TurboJPEG

TurboJPEG API. More...

Data Structures
struct	tjscalingfactor
	Scaling factor. More...
struct	tjregion
	Cropping region. More...
struct	tjtransform
	Lossless transform. More...

Macros
#define	TJ_NUMSAMP
	The number of chrominance subsampling options. More...
#define	TJ_NUMPF
	The number of pixel formats. More...
#define	TJ_NUMCS
	The number of JPEG colorspaces. More...
#define	TJFLAG_BOTTOMUP
	The uncompressed source/destination image is stored in bottom-up (Windows, OpenGL) order, not top-down (X11) order. More...
#define	TJFLAG_FASTUPSAMPLE
	When decompressing an image that was compressed using chrominance subsampling, use the fastest chrominance upsampling algorithm available in the underlying codec. More...
#define	TJFLAG_NOREALLOC
	Disable buffer (re)allocation. More...
#define	TJFLAG_FASTDCT
	Use the fastest DCT/IDCT algorithm available in the underlying codec. More...
#define	TJFLAG_ACCURATEDCT
	Use the most accurate DCT/IDCT algorithm available in the underlying codec. More...
#define	TJFLAG_STOPONWARNING
	Immediately discontinue the current compression/decompression/transform operation if the underlying codec throws a warning (non-fatal error). More...
#define	TJFLAG_PROGRESSIVE
	Use progressive entropy coding in JPEG images generated by the compression and transform functions. More...
#define	TJ_NUMERR
	The number of error codes. More...
#define	TJ_NUMXOP
	The number of transform operations. More...
#define	TJXOPT_PERFECT
	This option will cause tjTransform() to return an error if the transform is not perfect. More...
#define	TJXOPT_TRIM
	This option will cause tjTransform() to discard any partial MCU blocks that cannot be transformed. More...
#define	TJXOPT_CROP
	This option will enable lossless cropping. More...
#define	TJXOPT_GRAY
	This option will discard the color data in the input image and produce a grayscale output image. More...
#define	TJXOPT_NOOUTPUT
	This option will prevent tjTransform() from outputting a JPEG image for this particular transform (this can be used in conjunction with a custom filter to capture the transformed DCT coefficients without transcoding them.) More...
#define	TJXOPT_PROGRESSIVE
	This option will enable progressive entropy coding in the output image generated by this particular transform. More...
#define	TJXOPT_COPYNONE
	This option will prevent tjTransform() from copying any extra markers (including EXIF and ICC profile data) from the source image to the output image. More...
#define	TJPAD(width)
	Pad the given width to the nearest 32-bit boundary. More...
#define	TJSCALED(dimension, scalingFactor)
	Compute the scaled value of dimension using the given scaling factor. More...

Typedefs
typedef struct tjtransform	tjtransform
	Lossless transform. More...
typedef void *	tjhandle
	TurboJPEG instance handle. More...

Enumerations
enum	TJSAMP {   TJSAMP_444, TJSAMP_422, TJSAMP_420, TJSAMP_GRAY,   TJSAMP_440, TJSAMP_411 }
	Chrominance subsampling options. More...
enum	TJPF {   TJPF_RGB, TJPF_BGR, TJPF_RGBX, TJPF_BGRX,   TJPF_XBGR, TJPF_XRGB, TJPF_GRAY, TJPF_RGBA,   TJPF_BGRA, TJPF_ABGR, TJPF_ARGB, TJPF_CMYK,   TJPF_UNKNOWN }
	Pixel formats. More...
enum	TJCS {   TJCS_RGB, TJCS_YCbCr, TJCS_GRAY, TJCS_CMYK,   TJCS_YCCK }
	JPEG colorspaces. More...
enum	TJERR { TJERR_WARNING, TJERR_FATAL }
	Error codes. More...
enum	TJXOP {   TJXOP_NONE, TJXOP_HFLIP, TJXOP_VFLIP, TJXOP_TRANSPOSE,   TJXOP_TRANSVERSE, TJXOP_ROT90, TJXOP_ROT180, TJXOP_ROT270 }
	Transform operations for tjTransform() More...

Functions
DLLEXPORT tjhandle	tjInitCompress (void)
	Create a TurboJPEG compressor instance. More...
DLLEXPORT int	tjCompress2 (tjhandle handle, const unsigned char *srcBuf, int width, int pitch, int height, int pixelFormat, unsigned char **jpegBuf, unsigned long *jpegSize, int jpegSubsamp, int jpegQual, int flags)
	Compress an RGB, grayscale, or CMYK image into a JPEG image. More...
DLLEXPORT int	tjCompressFromYUV (tjhandle handle, const unsigned char *srcBuf, int width, int pad, int height, int subsamp, unsigned char **jpegBuf, unsigned long *jpegSize, int jpegQual, int flags)
	Compress a YUV planar image into a JPEG image. More...
DLLEXPORT int	tjCompressFromYUVPlanes (tjhandle handle, const unsigned char **srcPlanes, int width, const int *strides, int height, int subsamp, unsigned char **jpegBuf, unsigned long *jpegSize, int jpegQual, int flags)
	Compress a set of Y, U (Cb), and V (Cr) image planes into a JPEG image. More...
DLLEXPORT unsigned long	tjBufSize (int width, int height, int jpegSubsamp)
	The maximum size of the buffer (in bytes) required to hold a JPEG image with the given parameters. More...
DLLEXPORT unsigned long	tjBufSizeYUV2 (int width, int pad, int height, int subsamp)
	The size of the buffer (in bytes) required to hold a YUV planar image with the given parameters. More...
DLLEXPORT unsigned long	tjPlaneSizeYUV (int componentID, int width, int stride, int height, int subsamp)
	The size of the buffer (in bytes) required to hold a YUV image plane with the given parameters. More...
DLLEXPORT int	tjPlaneWidth (int componentID, int width, int subsamp)
	The plane width of a YUV image plane with the given parameters. More...
DLLEXPORT int	tjPlaneHeight (int componentID, int height, int subsamp)
	The plane height of a YUV image plane with the given parameters. More...
DLLEXPORT int	tjEncodeYUV3 (tjhandle handle, const unsigned char *srcBuf, int width, int pitch, int height, int pixelFormat, unsigned char *dstBuf, int pad, int subsamp, int flags)
	Encode an RGB or grayscale image into a YUV planar image. More...
DLLEXPORT int	tjEncodeYUVPlanes (tjhandle handle, const unsigned char *srcBuf, int width, int pitch, int height, int pixelFormat, unsigned char **dstPlanes, int *strides, int subsamp, int flags)
	Encode an RGB or grayscale image into separate Y, U (Cb), and V (Cr) image planes. More...
DLLEXPORT tjhandle	tjInitDecompress (void)
	Create a TurboJPEG decompressor instance. More...
DLLEXPORT int	tjDecompressHeader3 (tjhandle handle, const unsigned char *jpegBuf, unsigned long jpegSize, int *width, int *height, int *jpegSubsamp, int *jpegColorspace)
	Retrieve information about a JPEG image without decompressing it. More...
DLLEXPORT tjscalingfactor *	tjGetScalingFactors (int *numscalingfactors)
	Returns a list of fractional scaling factors that the JPEG decompressor in this implementation of TurboJPEG supports. More...
DLLEXPORT int	tjDecompress2 (tjhandle handle, const unsigned char *jpegBuf, unsigned long jpegSize, unsigned char *dstBuf, int width, int pitch, int height, int pixelFormat, int flags)
	Decompress a JPEG image to an RGB, grayscale, or CMYK image. More...
DLLEXPORT int	tjDecompressToYUV2 (tjhandle handle, const unsigned char *jpegBuf, unsigned long jpegSize, unsigned char *dstBuf, int width, int pad, int height, int flags)
	Decompress a JPEG image to a YUV planar image. More...
DLLEXPORT int	tjDecompressToYUVPlanes (tjhandle handle, const unsigned char *jpegBuf, unsigned long jpegSize, unsigned char **dstPlanes, int width, int *strides, int height, int flags)
	Decompress a JPEG image into separate Y, U (Cb), and V (Cr) image planes. More...
DLLEXPORT int	tjDecodeYUV (tjhandle handle, const unsigned char *srcBuf, int pad, int subsamp, unsigned char *dstBuf, int width, int pitch, int height, int pixelFormat, int flags)
	Decode a YUV planar image into an RGB or grayscale image. More...
DLLEXPORT int	tjDecodeYUVPlanes (tjhandle handle, const unsigned char **srcPlanes, const int *strides, int subsamp, unsigned char *dstBuf, int width, int pitch, int height, int pixelFormat, int flags)
	Decode a set of Y, U (Cb), and V (Cr) image planes into an RGB or grayscale image. More...
DLLEXPORT tjhandle	tjInitTransform (void)
	Create a new TurboJPEG transformer instance. More...
DLLEXPORT int	tjTransform (tjhandle handle, const unsigned char *jpegBuf, unsigned long jpegSize, int n, unsigned char **dstBufs, unsigned long *dstSizes, tjtransform *transforms, int flags)
	Losslessly transform a JPEG image into another JPEG image. More...
DLLEXPORT int	tjDestroy (tjhandle handle)
	Destroy a TurboJPEG compressor, decompressor, or transformer instance. More...
DLLEXPORT unsigned char *	tjAlloc (int bytes)
	Allocate an image buffer for use with TurboJPEG. More...
DLLEXPORT unsigned char *	tjLoadImage (const char *filename, int *width, int align, int *height, int *pixelFormat, int flags)
	Load an uncompressed image from disk into memory. More...
DLLEXPORT int	tjSaveImage (const char *filename, unsigned char *buffer, int width, int pitch, int height, int pixelFormat, int flags)
	Save an uncompressed image from memory to disk. More...
DLLEXPORT void	tjFree (unsigned char *buffer)
	Free an image buffer previously allocated by TurboJPEG. More...
DLLEXPORT char *	tjGetErrorStr2 (tjhandle handle)
	Returns a descriptive error message explaining why the last command failed. More...
DLLEXPORT int	tjGetErrorCode (tjhandle handle)
	Returns a code indicating the severity of the last error. More...

Variables
static const int	tjMCUWidth [TJ_NUMSAMP]
	MCU block width (in pixels) for a given level of chrominance subsampling. More...
static const int	tjMCUHeight [TJ_NUMSAMP]
	MCU block height (in pixels) for a given level of chrominance subsampling. More...
static const int	tjRedOffset [TJ_NUMPF]
	Red offset (in bytes) for a given pixel format. More...
static const int	tjGreenOffset [TJ_NUMPF]
	Green offset (in bytes) for a given pixel format. More...
static const int	tjBlueOffset [TJ_NUMPF]
	Blue offset (in bytes) for a given pixel format. More...
static const int	tjAlphaOffset [TJ_NUMPF]
	Alpha offset (in bytes) for a given pixel format. More...
static const int	tjPixelSize [TJ_NUMPF]
	Pixel size (in bytes) for a given pixel format. More...

Detailed Description

TurboJPEG API.

This API provides an interface for generating, decoding, and transforming planar YUV and JPEG images in memory.

YUV Image Format Notes

Technically, the JPEG format uses the YCbCr colorspace (which is technically not a colorspace but a color transform), but per the convention of the digital video community, the TurboJPEG API uses "YUV" to refer to an image format consisting of Y, Cb, and Cr image planes.

Each plane is simply a 2D array of bytes, each byte representing the value of one of the components (Y, Cb, or Cr) at a particular location in the image. The width and height of each plane are determined by the image width, height, and level of chrominance subsampling. The luminance plane width is the image width padded to the nearest multiple of the horizontal subsampling factor (2 in the case of 4:2:0 and 4:2:2, 4 in the case of 4:1:1, 1 in the case of 4:4:4 or grayscale.) Similarly, the luminance plane height is the image height padded to the nearest multiple of the vertical subsampling factor (2 in the case of 4:2:0 or 4:4:0, 1 in the case of 4:4:4 or grayscale.) This is irrespective of any additional padding that may be specified as an argument to the various YUV functions. The chrominance plane width is equal to the luminance plane width divided by the horizontal subsampling factor, and the chrominance plane height is equal to the luminance plane height divided by the vertical subsampling factor.

For example, if the source image is 35 x 35 pixels and 4:2:2 subsampling is used, then the luminance plane would be 36 x 35 bytes, and each of the chrominance planes would be 18 x 35 bytes. If you specify a line padding of 4 bytes on top of this, then the luminance plane would be 36 x 35 bytes, and each of the chrominance planes would be 20 x 35 bytes.

Macro Definition Documentation

#define TJ_NUMCS

The number of JPEG colorspaces.

#define TJ_NUMERR

The number of error codes.

#define TJ_NUMPF

The number of pixel formats.

#define TJ_NUMSAMP

The number of chrominance subsampling options.

#define TJ_NUMXOP

The number of transform operations.

#define TJFLAG_ACCURATEDCT

Use the most accurate DCT/IDCT algorithm available in the underlying codec.

The default if this flag is not specified is implementation-specific. For example, the implementation of TurboJPEG for libjpeg[-turbo] uses the fast algorithm by default when compressing, because this has been shown to have only a very slight effect on accuracy, but it uses the accurate algorithm when decompressing, because this has been shown to have a larger effect.

#define TJFLAG_BOTTOMUP

The uncompressed source/destination image is stored in bottom-up (Windows, OpenGL) order, not top-down (X11) order.

#define TJFLAG_FASTDCT

Use the fastest DCT/IDCT algorithm available in the underlying codec.

The default if this flag is not specified is implementation-specific. For example, the implementation of TurboJPEG for libjpeg[-turbo] uses the fast algorithm by default when compressing, because this has been shown to have only a very slight effect on accuracy, but it uses the accurate algorithm when decompressing, because this has been shown to have a larger effect.

#define TJFLAG_FASTUPSAMPLE

When decompressing an image that was compressed using chrominance subsampling, use the fastest chrominance upsampling algorithm available in the underlying codec.

The default is to use smooth upsampling, which creates a smooth transition between neighboring chrominance components in order to reduce upsampling artifacts in the decompressed image.

#define TJFLAG_NOREALLOC

Disable buffer (re)allocation.

If passed to one of the JPEG compression or transform functions, this flag will cause those functions to generate an error if the JPEG image buffer is invalid or too small rather than attempting to allocate or reallocate that buffer. This reproduces the behavior of earlier versions of TurboJPEG.

#define TJFLAG_PROGRESSIVE

Use progressive entropy coding in JPEG images generated by the compression and transform functions.

Progressive entropy coding will generally improve compression relative to baseline entropy coding (the default), but it will reduce compression and decompression performance considerably.

#define TJFLAG_STOPONWARNING

Immediately discontinue the current compression/decompression/transform operation if the underlying codec throws a warning (non-fatal error).

The default behavior is to allow the operation to complete unless a fatal error is encountered.

#define TJPAD

(

width

)

Pad the given width to the nearest 32-bit boundary.

#define TJSCALED	(		dimension,
			scalingFactor
	)

Compute the scaled value of dimension using the given scaling factor.

This macro performs the integer equivalent of ceil(dimension * scalingFactor).

#define TJXOPT_COPYNONE

This option will prevent tjTransform() from copying any extra markers (including EXIF and ICC profile data) from the source image to the output image.

#define TJXOPT_CROP

This option will enable lossless cropping.

See tjTransform() for more information.

#define TJXOPT_GRAY

This option will discard the color data in the input image and produce a grayscale output image.

#define TJXOPT_NOOUTPUT

This option will prevent tjTransform() from outputting a JPEG image for this particular transform (this can be used in conjunction with a custom filter to capture the transformed DCT coefficients without transcoding them.)

#define TJXOPT_PERFECT

This option will cause tjTransform() to return an error if the transform is not perfect.

Lossless transforms operate on MCU blocks, whose size depends on the level of chrominance subsampling used (see tjMCUWidth and tjMCUHeight.) If the image's width or height is not evenly divisible by the MCU block size, then there will be partial MCU blocks on the right and/or bottom edges. It is not possible to move these partial MCU blocks to the top or left of the image, so any transform that would require that is "imperfect." If this option is not specified, then any partial MCU blocks that cannot be transformed will be left in place, which will create odd-looking strips on the right or bottom edge of the image.

#define TJXOPT_PROGRESSIVE

This option will enable progressive entropy coding in the output image generated by this particular transform.

Progressive entropy coding will generally improve compression relative to baseline entropy coding (the default), but it will reduce compression and decompression performance considerably.

#define TJXOPT_TRIM

This option will cause tjTransform() to discard any partial MCU blocks that cannot be transformed.

Typedef Documentation

typedef void* tjhandle

TurboJPEG instance handle.

typedef struct tjtransform tjtransform

Lossless transform.

Enumeration Type Documentation

enum TJCS

JPEG colorspaces.

Enumerator
TJCS_RGB	RGB colorspace. When compressing the JPEG image, the R, G, and B components in the source image are reordered into image planes, but no colorspace conversion or subsampling is performed. RGB JPEG images can be decompressed to any of the extended RGB pixel formats or grayscale, but they cannot be decompressed to YUV images.
TJCS_YCbCr	YCbCr colorspace. YCbCr is not an absolute colorspace but rather a mathematical transformation of RGB designed solely for storage and transmission. YCbCr images must be converted to RGB before they can actually be displayed. In the YCbCr colorspace, the Y (luminance) component represents the black & white portion of the original image, and the Cb and Cr (chrominance) components represent the color portion of the original image. Originally, the analog equivalent of this transformation allowed the same signal to drive both black & white and color televisions, but JPEG images use YCbCr primarily because it allows the color data to be optionally subsampled for the purposes of reducing bandwidth or disk space. YCbCr is the most common JPEG colorspace, and YCbCr JPEG images can be compressed from and decompressed to any of the extended RGB pixel formats or grayscale, or they can be decompressed to YUV planar images.
TJCS_GRAY	Grayscale colorspace. The JPEG image retains only the luminance data (Y component), and any color data from the source image is discarded. Grayscale JPEG images can be compressed from and decompressed to any of the extended RGB pixel formats or grayscale, or they can be decompressed to YUV planar images.
TJCS_CMYK	CMYK colorspace. When compressing the JPEG image, the C, M, Y, and K components in the source image are reordered into image planes, but no colorspace conversion or subsampling is performed. CMYK JPEG images can only be decompressed to CMYK pixels.
TJCS_YCCK	YCCK colorspace. YCCK (AKA "YCbCrK") is not an absolute colorspace but rather a mathematical transformation of CMYK designed solely for storage and transmission. It is to CMYK as YCbCr is to RGB. CMYK pixels can be reversibly transformed into YCCK, and as with YCbCr, the chrominance components in the YCCK pixels can be subsampled without incurring major perceptual loss. YCCK JPEG images can only be compressed from and decompressed to CMYK pixels.

enum TJERR

Error codes.

Enumerator
TJERR_WARNING	The error was non-fatal and recoverable, but the image may still be corrupt.
TJERR_FATAL	The error was fatal and non-recoverable.

enum TJPF

Pixel formats.

Enumerator
TJPF_RGB	RGB pixel format. The red, green, and blue components in the image are stored in 3-byte pixels in the order R, G, B from lowest to highest byte address within each pixel.
TJPF_BGR	BGR pixel format. The red, green, and blue components in the image are stored in 3-byte pixels in the order B, G, R from lowest to highest byte address within each pixel.
TJPF_RGBX	RGBX pixel format. The red, green, and blue components in the image are stored in 4-byte pixels in the order R, G, B from lowest to highest byte address within each pixel. The X component is ignored when compressing and undefined when decompressing.
TJPF_BGRX	BGRX pixel format. The red, green, and blue components in the image are stored in 4-byte pixels in the order B, G, R from lowest to highest byte address within each pixel. The X component is ignored when compressing and undefined when decompressing.
TJPF_XBGR	XBGR pixel format. The red, green, and blue components in the image are stored in 4-byte pixels in the order R, G, B from highest to lowest byte address within each pixel. The X component is ignored when compressing and undefined when decompressing.
TJPF_XRGB	XRGB pixel format. The red, green, and blue components in the image are stored in 4-byte pixels in the order B, G, R from highest to lowest byte address within each pixel. The X component is ignored when compressing and undefined when decompressing.
TJPF_GRAY	Grayscale pixel format. Each 1-byte pixel represents a luminance (brightness) level from 0 to 255.
TJPF_RGBA	RGBA pixel format. This is the same as TJPF_RGBX, except that when decompressing, the X component is guaranteed to be 0xFF, which can be interpreted as an opaque alpha channel.
TJPF_BGRA	BGRA pixel format. This is the same as TJPF_BGRX, except that when decompressing, the X component is guaranteed to be 0xFF, which can be interpreted as an opaque alpha channel.
TJPF_ABGR	ABGR pixel format. This is the same as TJPF_XBGR, except that when decompressing, the X component is guaranteed to be 0xFF, which can be interpreted as an opaque alpha channel.
TJPF_ARGB	ARGB pixel format. This is the same as TJPF_XRGB, except that when decompressing, the X component is guaranteed to be 0xFF, which can be interpreted as an opaque alpha channel.
TJPF_CMYK	CMYK pixel format. Unlike RGB, which is an additive color model used primarily for display, CMYK (Cyan/Magenta/Yellow/Key) is a subtractive color model used primarily for printing. In the CMYK color model, the value of each color component typically corresponds to an amount of cyan, magenta, yellow, or black ink that is applied to a white background. In order to convert between CMYK and RGB, it is necessary to use a color management system (CMS.) A CMS will attempt to map colors within the printer's gamut to perceptually similar colors in the display's gamut and vice versa, but the mapping is typically not 1:1 or reversible, nor can it be defined with a simple formula. Thus, such a conversion is out of scope for a codec library. However, the TurboJPEG API allows for compressing CMYK pixels into a YCCK JPEG image (see TJCS_YCCK) and decompressing YCCK JPEG images into CMYK pixels.
TJPF_UNKNOWN	Unknown pixel format. Currently this is only used by tjLoadImage().

enum TJSAMP

Chrominance subsampling options.

When pixels are converted from RGB to YCbCr (see TJCS_YCbCr) or from CMYK to YCCK (see TJCS_YCCK) as part of the JPEG compression process, some of the Cb and Cr (chrominance) components can be discarded or averaged together to produce a smaller image with little perceptible loss of image clarity (the human eye is more sensitive to small changes in brightness than to small changes in color.) This is called "chrominance subsampling".

Enumerator
TJSAMP_444	4:4:4 chrominance subsampling (no chrominance subsampling). The JPEG or YUV image will contain one chrominance component for every pixel in the source image.
TJSAMP_422	4:2:2 chrominance subsampling. The JPEG or YUV image will contain one chrominance component for every 2x1 block of pixels in the source image.
TJSAMP_420	4:2:0 chrominance subsampling. The JPEG or YUV image will contain one chrominance component for every 2x2 block of pixels in the source image.
TJSAMP_GRAY	Grayscale. The JPEG or YUV image will contain no chrominance components.
TJSAMP_440	4:4:0 chrominance subsampling. The JPEG or YUV image will contain one chrominance component for every 1x2 block of pixels in the source image. Note 4:4:0 subsampling is not fully accelerated in libjpeg-turbo.
TJSAMP_411	4:1:1 chrominance subsampling. The JPEG or YUV image will contain one chrominance component for every 4x1 block of pixels in the source image. JPEG images compressed with 4:1:1 subsampling will be almost exactly the same size as those compressed with 4:2:0 subsampling, and in the aggregate, both subsampling methods produce approximately the same perceptual quality. However, 4:1:1 is better able to reproduce sharp horizontal features. Note 4:1:1 subsampling is not fully accelerated in libjpeg-turbo.

enum TJXOP

Transform operations for tjTransform()

Enumerator
TJXOP_NONE	Do not transform the position of the image pixels.
TJXOP_HFLIP	Flip (mirror) image horizontally. This transform is imperfect if there are any partial MCU blocks on the right edge (see TJXOPT_PERFECT.)
TJXOP_VFLIP	Flip (mirror) image vertically. This transform is imperfect if there are any partial MCU blocks on the bottom edge (see TJXOPT_PERFECT.)
TJXOP_TRANSPOSE	Transpose image (flip/mirror along upper left to lower right axis.) This transform is always perfect.
TJXOP_TRANSVERSE	Transverse transpose image (flip/mirror along upper right to lower left axis.) This transform is imperfect if there are any partial MCU blocks in the image (see TJXOPT_PERFECT.)
TJXOP_ROT90	Rotate image clockwise by 90 degrees. This transform is imperfect if there are any partial MCU blocks on the bottom edge (see TJXOPT_PERFECT.)
TJXOP_ROT180	Rotate image 180 degrees. This transform is imperfect if there are any partial MCU blocks in the image (see TJXOPT_PERFECT.)
TJXOP_ROT270	Rotate image counter-clockwise by 90 degrees. This transform is imperfect if there are any partial MCU blocks on the right edge (see TJXOPT_PERFECT.)

Function Documentation

DLLEXPORT unsigned char* tjAlloc

(

int

bytes

)

Allocate an image buffer for use with TurboJPEG.

You should always use this function to allocate the JPEG destination buffer(s) for the compression and transform functions unless you are disabling automatic buffer (re)allocation (by setting TJFLAG_NOREALLOC.)

Parameters

bytes

the number of bytes to allocate

Returns

a pointer to a newly-allocated buffer with the specified number of bytes.

See Also

tjFree()

DLLEXPORT unsigned long tjBufSize	(	int	width,
		int	height,
		int	jpegSubsamp
	)

The maximum size of the buffer (in bytes) required to hold a JPEG image with the given parameters.

The number of bytes returned by this function is larger than the size of the uncompressed source image. The reason for this is that the JPEG format uses 16-bit coefficients, and it is thus possible for a very high-quality JPEG image with very high-frequency content to expand rather than compress when converted to the JPEG format. Such images represent a very rare corner case, but since there is no way to predict the size of a JPEG image prior to compression, the corner case has to be handled.

Parameters

width	width (in pixels) of the image
height	height (in pixels) of the image
jpegSubsamp	the level of chrominance subsampling to be used when generating the JPEG image (see Chrominance subsampling options.)

Returns

the maximum size of the buffer (in bytes) required to hold the image, or -1 if the arguments are out of bounds.

DLLEXPORT unsigned long tjBufSizeYUV2	(	int	width,
		int	pad,
		int	height,
		int	subsamp
	)

The size of the buffer (in bytes) required to hold a YUV planar image with the given parameters.

Parameters

width	width (in pixels) of the image
pad	the width of each line in each plane of the image is padded to the nearest multiple of this number of bytes (must be a power of 2.)
height	height (in pixels) of the image
subsamp	level of chrominance subsampling in the image (see Chrominance subsampling options.)

Returns

the size of the buffer (in bytes) required to hold the image, or -1 if the arguments are out of bounds.

DLLEXPORT int tjCompress2	(	tjhandle	handle,
		const unsigned char *	srcBuf,
		int	width,
		int	pitch,
		int	height,
		int	pixelFormat,
		unsigned char **	jpegBuf,
		unsigned long *	jpegSize,
		int	jpegSubsamp,
		int	jpegQual,
		int	flags
	)

Compress an RGB, grayscale, or CMYK image into a JPEG image.

Parameters

handle	a handle to a TurboJPEG compressor or transformer instance
srcBuf	pointer to an image buffer containing RGB, grayscale, or CMYK pixels to be compressed
width	width (in pixels) of the source image
pitch	bytes per line in the source image. Normally, this should be width * tjPixelSize[pixelFormat] if the image is unpadded, or TJPAD(width * tjPixelSize[pixelFormat]) if each line of the image is padded to the nearest 32-bit boundary, as is the case for Windows bitmaps. You can also be clever and use this parameter to skip lines, etc. Setting this parameter to 0 is the equivalent of setting it to width * tjPixelSize[pixelFormat].
height	height (in pixels) of the source image
pixelFormat	pixel format of the source image (see Pixel formats.)
jpegBuf	address of a pointer to an image buffer that will receive the JPEG image. TurboJPEG has the ability to reallocate the JPEG buffer to accommodate the size of the JPEG image. Thus, you can choose to: pre-allocate the JPEG buffer with an arbitrary size using tjAlloc() and let TurboJPEG grow the buffer as needed, set *jpegBuf to NULL to tell TurboJPEG to allocate the buffer for you, or pre-allocate the buffer to a "worst case" size determined by calling tjBufSize(). This should ensure that the buffer never has to be re-allocated (setting TJFLAG_NOREALLOC guarantees that it won't be.) If you choose option 1, *jpegSize should be set to the size of your pre-allocated buffer. In any case, unless you have set TJFLAG_NOREALLOC, you should always check *jpegBuf upon return from this function, as it may have changed.
jpegSize	pointer to an unsigned long variable that holds the size of the JPEG image buffer. If *jpegBuf points to a pre-allocated buffer, then *jpegSize should be set to the size of the buffer. Upon return, *jpegSize will contain the size of the JPEG image (in bytes.) If *jpegBuf points to a JPEG image buffer that is being reused from a previous call to one of the JPEG compression functions, then *jpegSize is ignored.
jpegSubsamp	the level of chrominance subsampling to be used when generating the JPEG image (see Chrominance subsampling options.)
jpegQual	the image quality of the generated JPEG image (1 = worst, 100 = best)
flags	the bitwise OR of one or more of the flags

Returns

0 if successful, or -1 if an error occurred (see tjGetErrorStr2() and tjGetErrorCode().)

DLLEXPORT int tjCompressFromYUV	(	tjhandle	handle,
		const unsigned char *	srcBuf,
		int	width,
		int	pad,
		int	height,
		int	subsamp,
		unsigned char **	jpegBuf,
		unsigned long *	jpegSize,
		int	jpegQual,
		int	flags
	)

Compress a YUV planar image into a JPEG image.

Parameters

handle	a handle to a TurboJPEG compressor or transformer instance
srcBuf	pointer to an image buffer containing a YUV planar image to be compressed. The size of this buffer should match the value returned by tjBufSizeYUV2() for the given image width, height, padding, and level of chrominance subsampling. The Y, U (Cb), and V (Cr) image planes should be stored sequentially in the source buffer (refer to YUV Image Format Notes.)
width	width (in pixels) of the source image. If the width is not an even multiple of the MCU block width (see tjMCUWidth), then an intermediate buffer copy will be performed within TurboJPEG.
pad	the line padding used in the source image. For instance, if each line in each plane of the YUV image is padded to the nearest multiple of 4 bytes, then pad should be set to 4.
height	height (in pixels) of the source image. If the height is not an even multiple of the MCU block height (see tjMCUHeight), then an intermediate buffer copy will be performed within TurboJPEG.
subsamp	the level of chrominance subsampling used in the source image (see Chrominance subsampling options.)
jpegBuf	address of a pointer to an image buffer that will receive the JPEG image. TurboJPEG has the ability to reallocate the JPEG buffer to accommodate the size of the JPEG image. Thus, you can choose to: pre-allocate the JPEG buffer with an arbitrary size using tjAlloc() and let TurboJPEG grow the buffer as needed, set *jpegBuf to NULL to tell TurboJPEG to allocate the buffer for you, or pre-allocate the buffer to a "worst case" size determined by calling tjBufSize(). This should ensure that the buffer never has to be re-allocated (setting TJFLAG_NOREALLOC guarantees that it won't be.) If you choose option 1, *jpegSize should be set to the size of your pre-allocated buffer. In any case, unless you have set TJFLAG_NOREALLOC, you should always check *jpegBuf upon return from this function, as it may have changed.
jpegSize	pointer to an unsigned long variable that holds the size of the JPEG image buffer. If *jpegBuf points to a pre-allocated buffer, then *jpegSize should be set to the size of the buffer. Upon return, *jpegSize will contain the size of the JPEG image (in bytes.) If *jpegBuf points to a JPEG image buffer that is being reused from a previous call to one of the JPEG compression functions, then *jpegSize is ignored.
jpegQual	the image quality of the generated JPEG image (1 = worst, 100 = best)
flags	the bitwise OR of one or more of the flags

Returns

0 if successful, or -1 if an error occurred (see tjGetErrorStr2() and tjGetErrorCode().)

DLLEXPORT int tjCompressFromYUVPlanes	(	tjhandle	handle,
		const unsigned char **	srcPlanes,
		int	width,
		const int *	strides,
		int	height,
		int	subsamp,
		unsigned char **	jpegBuf,
		unsigned long *	jpegSize,
		int	jpegQual,
		int	flags
	)

Compress a set of Y, U (Cb), and V (Cr) image planes into a JPEG image.

Parameters

handle	a handle to a TurboJPEG compressor or transformer instance
srcPlanes	an array of pointers to Y, U (Cb), and V (Cr) image planes (or just a Y plane, if compressing a grayscale image) that contain a YUV image to be compressed. These planes can be contiguous or non-contiguous in memory. The size of each plane should match the value returned by tjPlaneSizeYUV() for the given image width, height, strides, and level of chrominance subsampling. Refer to YUV Image Format Notes for more details.
width	width (in pixels) of the source image. If the width is not an even multiple of the MCU block width (see tjMCUWidth), then an intermediate buffer copy will be performed within TurboJPEG.
strides	an array of integers, each specifying the number of bytes per line in the corresponding plane of the YUV source image. Setting the stride for any plane to 0 is the same as setting it to the plane width (see YUV Image Format Notes.) If strides is NULL, then the strides for all planes will be set to their respective plane widths. You can adjust the strides in order to specify an arbitrary amount of line padding in each plane or to create a JPEG image from a subregion of a larger YUV planar image.
height	height (in pixels) of the source image. If the height is not an even multiple of the MCU block height (see tjMCUHeight), then an intermediate buffer copy will be performed within TurboJPEG.
subsamp	the level of chrominance subsampling used in the source image (see Chrominance subsampling options.)
jpegBuf	address of a pointer to an image buffer that will receive the JPEG image. TurboJPEG has the ability to reallocate the JPEG buffer to accommodate the size of the JPEG image. Thus, you can choose to: pre-allocate the JPEG buffer with an arbitrary size using tjAlloc() and let TurboJPEG grow the buffer as needed, set *jpegBuf to NULL to tell TurboJPEG to allocate the buffer for you, or pre-allocate the buffer to a "worst case" size determined by calling tjBufSize(). This should ensure that the buffer never has to be re-allocated (setting TJFLAG_NOREALLOC guarantees that it won't be.) If you choose option 1, *jpegSize should be set to the size of your pre-allocated buffer. In any case, unless you have set TJFLAG_NOREALLOC, you should always check *jpegBuf upon return from this function, as it may have changed.
jpegSize	pointer to an unsigned long variable that holds the size of the JPEG image buffer. If *jpegBuf points to a pre-allocated buffer, then *jpegSize should be set to the size of the buffer. Upon return, *jpegSize will contain the size of the JPEG image (in bytes.) If *jpegBuf points to a JPEG image buffer that is being reused from a previous call to one of the JPEG compression functions, then *jpegSize is ignored.
jpegQual	the image quality of the generated JPEG image (1 = worst, 100 = best)
flags	the bitwise OR of one or more of the flags

Returns

0 if successful, or -1 if an error occurred (see tjGetErrorStr2() and tjGetErrorCode().)

DLLEXPORT int tjDecodeYUV	(	tjhandle	handle,
		const unsigned char *	srcBuf,
		int	pad,
		int	subsamp,
		unsigned char *	dstBuf,
		int	width,
		int	pitch,
		int	height,
		int	pixelFormat,
		int	flags
	)

Decode a YUV planar image into an RGB or grayscale image.

This function uses the accelerated color conversion routines in the underlying codec but does not execute any of the other steps in the JPEG decompression process.

Parameters

handle	a handle to a TurboJPEG decompressor or transformer instance
srcBuf	pointer to an image buffer containing a YUV planar image to be decoded. The size of this buffer should match the value returned by tjBufSizeYUV2() for the given image width, height, padding, and level of chrominance subsampling. The Y, U (Cb), and V (Cr) image planes should be stored sequentially in the source buffer (refer to YUV Image Format Notes.)
pad	Use this parameter to specify that the width of each line in each plane of the YUV source image is padded to the nearest multiple of this number of bytes (must be a power of 2.)
subsamp	the level of chrominance subsampling used in the YUV source image (see Chrominance subsampling options.)
dstBuf	pointer to an image buffer that will receive the decoded image. This buffer should normally be pitch * height bytes in size, but the dstBuf pointer can also be used to decode into a specific region of a larger buffer.
width	width (in pixels) of the source and destination images
pitch	bytes per line in the destination image. Normally, this should be width * tjPixelSize[pixelFormat] if the destination image is unpadded, or TJPAD(width * tjPixelSize[pixelFormat]) if each line of the destination image should be padded to the nearest 32-bit boundary, as is the case for Windows bitmaps. You can also be clever and use the pitch parameter to skip lines, etc. Setting this parameter to 0 is the equivalent of setting it to width * tjPixelSize[pixelFormat].
height	height (in pixels) of the source and destination images
pixelFormat	pixel format of the destination image (see Pixel formats.)
flags	the bitwise OR of one or more of the flags

Returns

0 if successful, or -1 if an error occurred (see tjGetErrorStr2() and tjGetErrorCode().)

DLLEXPORT int tjDecodeYUVPlanes	(	tjhandle	handle,
		const unsigned char **	srcPlanes,
		const int *	strides,
		int	subsamp,
		unsigned char *	dstBuf,
		int	width,
		int	pitch,
		int	height,
		int	pixelFormat,
		int	flags
	)

Decode a set of Y, U (Cb), and V (Cr) image planes into an RGB or grayscale image.

This function uses the accelerated color conversion routines in the underlying codec but does not execute any of the other steps in the JPEG decompression process.

Parameters

handle	a handle to a TurboJPEG decompressor or transformer instance
srcPlanes	an array of pointers to Y, U (Cb), and V (Cr) image planes (or just a Y plane, if decoding a grayscale image) that contain a YUV image to be decoded. These planes can be contiguous or non-contiguous in memory. The size of each plane should match the value returned by tjPlaneSizeYUV() for the given image width, height, strides, and level of chrominance subsampling. Refer to YUV Image Format Notes for more details.
strides	an array of integers, each specifying the number of bytes per line in the corresponding plane of the YUV source image. Setting the stride for any plane to 0 is the same as setting it to the plane width (see YUV Image Format Notes.) If strides is NULL, then the strides for all planes will be set to their respective plane widths. You can adjust the strides in order to specify an arbitrary amount of line padding in each plane or to decode a subregion of a larger YUV planar image.
subsamp	the level of chrominance subsampling used in the YUV source image (see Chrominance subsampling options.)
dstBuf	pointer to an image buffer that will receive the decoded image. This buffer should normally be pitch * height bytes in size, but the dstBuf pointer can also be used to decode into a specific region of a larger buffer.
width	width (in pixels) of the source and destination images
pitch	bytes per line in the destination image. Normally, this should be width * tjPixelSize[pixelFormat] if the destination image is unpadded, or TJPAD(width * tjPixelSize[pixelFormat]) if each line of the destination image should be padded to the nearest 32-bit boundary, as is the case for Windows bitmaps. You can also be clever and use the pitch parameter to skip lines, etc. Setting this parameter to 0 is the equivalent of setting it to width * tjPixelSize[pixelFormat].
height	height (in pixels) of the source and destination images
pixelFormat	pixel format of the destination image (see Pixel formats.)
flags	the bitwise OR of one or more of the flags

Returns

0 if successful, or -1 if an error occurred (see tjGetErrorStr2() and tjGetErrorCode().)

DLLEXPORT int tjDecompress2	(	tjhandle	handle,
		const unsigned char *	jpegBuf,
		unsigned long	jpegSize,
		unsigned char *	dstBuf,
		int	width,
		int	pitch,
		int	height,
		int	pixelFormat,
		int	flags
	)

Decompress a JPEG image to an RGB, grayscale, or CMYK image.

Parameters

handle	a handle to a TurboJPEG decompressor or transformer instance
jpegBuf	pointer to a buffer containing the JPEG image to decompress
jpegSize	size of the JPEG image (in bytes)
dstBuf	pointer to an image buffer that will receive the decompressed image. This buffer should normally be pitch * scaledHeight bytes in size, where scaledHeight can be determined by calling TJSCALED() with the JPEG image height and one of the scaling factors returned by tjGetScalingFactors(). The dstBuf pointer may also be used to decompress into a specific region of a larger buffer.
width	desired width (in pixels) of the destination image. If this is different than the width of the JPEG image being decompressed, then TurboJPEG will use scaling in the JPEG decompressor to generate the largest possible image that will fit within the desired width. If width is set to 0, then only the height will be considered when determining the scaled image size.
pitch	bytes per line in the destination image. Normally, this is scaledWidth * tjPixelSize[pixelFormat] if the decompressed image is unpadded, else TJPAD(scaledWidth * tjPixelSize[pixelFormat]) if each line of the decompressed image is padded to the nearest 32-bit boundary, as is the case for Windows bitmaps. (NOTE: scaledWidth can be determined by calling TJSCALED() with the JPEG image width and one of the scaling factors returned by tjGetScalingFactors().) You can also be clever and use the pitch parameter to skip lines, etc. Setting this parameter to 0 is the equivalent of setting it to scaledWidth * tjPixelSize[pixelFormat].
height	desired height (in pixels) of the destination image. If this is different than the height of the JPEG image being decompressed, then TurboJPEG will use scaling in the JPEG decompressor to generate the largest possible image that will fit within the desired height. If height is set to 0, then only the width will be considered when determining the scaled image size.
pixelFormat	pixel format of the destination image (see Pixel formats.)
flags	the bitwise OR of one or more of the flags

Returns

0 if successful, or -1 if an error occurred (see tjGetErrorStr2() and tjGetErrorCode().)

DLLEXPORT int tjDecompressHeader3	(	tjhandle	handle,
		const unsigned char *	jpegBuf,
		unsigned long	jpegSize,
		int *	width,
		int *	height,
		int *	jpegSubsamp,
		int *	jpegColorspace
	)

Retrieve information about a JPEG image without decompressing it.

Parameters

handle	a handle to a TurboJPEG decompressor or transformer instance
jpegBuf	pointer to a buffer containing a JPEG image
jpegSize	size of the JPEG image (in bytes)
width	pointer to an integer variable that will receive the width (in pixels) of the JPEG image
height	pointer to an integer variable that will receive the height (in pixels) of the JPEG image
jpegSubsamp	pointer to an integer variable that will receive the level of chrominance subsampling used when the JPEG image was compressed (see Chrominance subsampling options.)
jpegColorspace	pointer to an integer variable that will receive one of the JPEG colorspace constants, indicating the colorspace of the JPEG image (see JPEG colorspaces.)

Returns

0 if successful, or -1 if an error occurred (see tjGetErrorStr2() and tjGetErrorCode().)

DLLEXPORT int tjDecompressToYUV2	(	tjhandle	handle,
		const unsigned char *	jpegBuf,
		unsigned long	jpegSize,
		unsigned char *	dstBuf,
		int	width,
		int	pad,
		int	height,
		int	flags
	)

Decompress a JPEG image to a YUV planar image.

This function performs JPEG decompression but leaves out the color conversion step, so a planar YUV image is generated instead of an RGB image.

Parameters

handle	a handle to a TurboJPEG decompressor or transformer instance
jpegBuf	pointer to a buffer containing the JPEG image to decompress
jpegSize	size of the JPEG image (in bytes)
dstBuf	pointer to an image buffer that will receive the YUV image. Use tjBufSizeYUV2() to determine the appropriate size for this buffer based on the image width, height, padding, and level of subsampling. The Y, U (Cb), and V (Cr) image planes will be stored sequentially in the buffer (refer to YUV Image Format Notes.)
width	desired width (in pixels) of the YUV image. If this is different than the width of the JPEG image being decompressed, then TurboJPEG will use scaling in the JPEG decompressor to generate the largest possible image that will fit within the desired width. If width is set to 0, then only the height will be considered when determining the scaled image size. If the scaled width is not an even multiple of the MCU block width (see tjMCUWidth), then an intermediate buffer copy will be performed within TurboJPEG.
pad	the width of each line in each plane of the YUV image will be padded to the nearest multiple of this number of bytes (must be a power of 2.) To generate images suitable for X Video, pad should be set to 4.
height	desired height (in pixels) of the YUV image. If this is different than the height of the JPEG image being decompressed, then TurboJPEG will use scaling in the JPEG decompressor to generate the largest possible image that will fit within the desired height. If height is set to 0, then only the width will be considered when determining the scaled image size. If the scaled height is not an even multiple of the MCU block height (see tjMCUHeight), then an intermediate buffer copy will be performed within TurboJPEG.
flags	the bitwise OR of one or more of the flags

Returns

0 if successful, or -1 if an error occurred (see tjGetErrorStr2() and tjGetErrorCode().)

DLLEXPORT int tjDecompressToYUVPlanes	(	tjhandle	handle,
		const unsigned char *	jpegBuf,
		unsigned long	jpegSize,
		unsigned char **	dstPlanes,
		int	width,
		int *	strides,
		int	height,
		int	flags
	)

Decompress a JPEG image into separate Y, U (Cb), and V (Cr) image planes.

This function performs JPEG decompression but leaves out the color conversion step, so a planar YUV image is generated instead of an RGB image.

Parameters

handle	a handle to a TurboJPEG decompressor or transformer instance
jpegBuf	pointer to a buffer containing the JPEG image to decompress
jpegSize	size of the JPEG image (in bytes)
dstPlanes	an array of pointers to Y, U (Cb), and V (Cr) image planes (or just a Y plane, if decompressing a grayscale image) that will receive the YUV image. These planes can be contiguous or non-contiguous in memory. Use tjPlaneSizeYUV() to determine the appropriate size for each plane based on the scaled image width, scaled image height, strides, and level of chrominance subsampling. Refer to YUV Image Format Notes for more details.
width	desired width (in pixels) of the YUV image. If this is different than the width of the JPEG image being decompressed, then TurboJPEG will use scaling in the JPEG decompressor to generate the largest possible image that will fit within the desired width. If width is set to 0, then only the height will be considered when determining the scaled image size. If the scaled width is not an even multiple of the MCU block width (see tjMCUWidth), then an intermediate buffer copy will be performed within TurboJPEG.
strides	an array of integers, each specifying the number of bytes per line in the corresponding plane of the output image. Setting the stride for any plane to 0 is the same as setting it to the scaled plane width (see YUV Image Format Notes.) If strides is NULL, then the strides for all planes will be set to their respective scaled plane widths. You can adjust the strides in order to add an arbitrary amount of line padding to each plane or to decompress the JPEG image into a subregion of a larger YUV planar image.
height	desired height (in pixels) of the YUV image. If this is different than the height of the JPEG image being decompressed, then TurboJPEG will use scaling in the JPEG decompressor to generate the largest possible image that will fit within the desired height. If height is set to 0, then only the width will be considered when determining the scaled image size. If the scaled height is not an even multiple of the MCU block height (see tjMCUHeight), then an intermediate buffer copy will be performed within TurboJPEG.
flags	the bitwise OR of one or more of the flags

Returns

0 if successful, or -1 if an error occurred (see tjGetErrorStr2() and tjGetErrorCode().)

DLLEXPORT int tjDestroy

(

tjhandle

handle

)

Destroy a TurboJPEG compressor, decompressor, or transformer instance.

Parameters

handle

a handle to a TurboJPEG compressor, decompressor or transformer instance

Returns

0 if successful, or -1 if an error occurred (see tjGetErrorStr2().)

DLLEXPORT int tjEncodeYUV3	(	tjhandle	handle,
		const unsigned char *	srcBuf,
		int	width,
		int	pitch,
		int	height,
		int	pixelFormat,
		unsigned char *	dstBuf,
		int	pad,
		int	subsamp,
		int	flags
	)

Encode an RGB or grayscale image into a YUV planar image.

This function uses the accelerated color conversion routines in the underlying codec but does not execute any of the other steps in the JPEG compression process.

Parameters

handle	a handle to a TurboJPEG compressor or transformer instance
srcBuf	pointer to an image buffer containing RGB or grayscale pixels to be encoded
width	width (in pixels) of the source image
pitch	bytes per line in the source image. Normally, this should be width * tjPixelSize[pixelFormat] if the image is unpadded, or TJPAD(width * tjPixelSize[pixelFormat]) if each line of the image is padded to the nearest 32-bit boundary, as is the case for Windows bitmaps. You can also be clever and use this parameter to skip lines, etc. Setting this parameter to 0 is the equivalent of setting it to width * tjPixelSize[pixelFormat].
height	height (in pixels) of the source image
pixelFormat	pixel format of the source image (see Pixel formats.)
dstBuf	pointer to an image buffer that will receive the YUV image. Use tjBufSizeYUV2() to determine the appropriate size for this buffer based on the image width, height, padding, and level of chrominance subsampling. The Y, U (Cb), and V (Cr) image planes will be stored sequentially in the buffer (refer to YUV Image Format Notes.)
pad	the width of each line in each plane of the YUV image will be padded to the nearest multiple of this number of bytes (must be a power of 2.) To generate images suitable for X Video, pad should be set to 4.
subsamp	the level of chrominance subsampling to be used when generating the YUV image (see Chrominance subsampling options.) To generate images suitable for X Video, subsamp should be set to TJSAMP_420. This produces an image compatible with the I420 (AKA "YUV420P") format.
flags	the bitwise OR of one or more of the flags

Returns

0 if successful, or -1 if an error occurred (see tjGetErrorStr2() and tjGetErrorCode().)

DLLEXPORT int tjEncodeYUVPlanes	(	tjhandle	handle,
		const unsigned char *	srcBuf,
		int	width,
		int	pitch,
		int	height,
		int	pixelFormat,
		unsigned char **	dstPlanes,
		int *	strides,
		int	subsamp,
		int	flags
	)

Encode an RGB or grayscale image into separate Y, U (Cb), and V (Cr) image planes.

This function uses the accelerated color conversion routines in the underlying codec but does not execute any of the other steps in the JPEG compression process.

Parameters

handle	a handle to a TurboJPEG compressor or transformer instance
srcBuf	pointer to an image buffer containing RGB or grayscale pixels to be encoded
width	width (in pixels) of the source image
pitch	bytes per line in the source image. Normally, this should be width * tjPixelSize[pixelFormat] if the image is unpadded, or TJPAD(width * tjPixelSize[pixelFormat]) if each line of the image is padded to the nearest 32-bit boundary, as is the case for Windows bitmaps. You can also be clever and use this parameter to skip lines, etc. Setting this parameter to 0 is the equivalent of setting it to width * tjPixelSize[pixelFormat].
height	height (in pixels) of the source image
pixelFormat	pixel format of the source image (see Pixel formats.)
dstPlanes	an array of pointers to Y, U (Cb), and V (Cr) image planes (or just a Y plane, if generating a grayscale image) that will receive the encoded image. These planes can be contiguous or non-contiguous in memory. Use tjPlaneSizeYUV() to determine the appropriate size for each plane based on the image width, height, strides, and level of chrominance subsampling. Refer to YUV Image Format Notes for more details.
strides	an array of integers, each specifying the number of bytes per line in the corresponding plane of the output image. Setting the stride for any plane to 0 is the same as setting it to the plane width (see YUV Image Format Notes.) If strides is NULL, then the strides for all planes will be set to their respective plane widths. You can adjust the strides in order to add an arbitrary amount of line padding to each plane or to encode an RGB or grayscale image into a subregion of a larger YUV planar image.
subsamp	the level of chrominance subsampling to be used when generating the YUV image (see Chrominance subsampling options.) To generate images suitable for X Video, subsamp should be set to TJSAMP_420. This produces an image compatible with the I420 (AKA "YUV420P") format.
flags	the bitwise OR of one or more of the flags

Returns

0 if successful, or -1 if an error occurred (see tjGetErrorStr2() and tjGetErrorCode().)

DLLEXPORT void tjFree

(

unsigned char *

buffer

)

Free an image buffer previously allocated by TurboJPEG.

You should always use this function to free JPEG destination buffer(s) that were automatically (re)allocated by the compression and transform functions or that were manually allocated using tjAlloc().

Parameters

buffer

address of the buffer to free

See Also

tjAlloc()

DLLEXPORT int tjGetErrorCode

(

tjhandle

handle

)

Returns a code indicating the severity of the last error.

See Error codes.

Parameters

handle

a handle to a TurboJPEG compressor, decompressor or transformer instance

Returns

a code indicating the severity of the last error. See Error codes.

DLLEXPORT char* tjGetErrorStr2

(

tjhandle

handle

)

Returns a descriptive error message explaining why the last command failed.

Parameters

handle

a handle to a TurboJPEG compressor, decompressor, or transformer instance, or NULL if the error was generated by a global function (but note that retrieving the error message for a global function is not thread-safe.)

Returns

a descriptive error message explaining why the last command failed.

DLLEXPORT tjscalingfactor* tjGetScalingFactors

(

int *

numscalingfactors

)

Returns a list of fractional scaling factors that the JPEG decompressor in this implementation of TurboJPEG supports.

Parameters

numscalingfactors

pointer to an integer variable that will receive the number of elements in the list

Returns

a pointer to a list of fractional scaling factors, or NULL if an error is encountered (see tjGetErrorStr2().)

DLLEXPORT tjhandle tjInitCompress

(

void

)

Create a TurboJPEG compressor instance.

Returns

a handle to the newly-created instance, or NULL if an error occurred (see tjGetErrorStr2().)

DLLEXPORT tjhandle tjInitDecompress

(

void

)

Create a TurboJPEG decompressor instance.

Returns

a handle to the newly-created instance, or NULL if an error occurred (see tjGetErrorStr2().)

DLLEXPORT tjhandle tjInitTransform

(

void

)

Create a new TurboJPEG transformer instance.

Returns

a handle to the newly-created instance, or NULL if an error occurred (see tjGetErrorStr2().)

DLLEXPORT unsigned char* tjLoadImage	(	const char *	filename,
		int *	width,
		int	align,
		int *	height,
		int *	pixelFormat,
		int	flags
	)

Load an uncompressed image from disk into memory.

Parameters

filename	name of a file containing an uncompressed image in Windows BMP or PBMPLUS (PPM/PGM) format
width	pointer to an integer variable that will receive the width (in pixels) of the uncompressed image
align	row alignment of the image buffer to be returned (must be a power of 2.) For instance, setting this parameter to 4 will cause all rows in the image buffer to be padded to the nearest 32-bit boundary, and setting this parameter to 1 will cause all rows in the image buffer to be unpadded.
height	pointer to an integer variable that will receive the height (in pixels) of the uncompressed image
pixelFormat	pointer to an integer variable that specifies or will receive the pixel format of the uncompressed image buffer. The behavior of tjLoadImage() will vary depending on the value of *pixelFormat passed to the function: TJPF_UNKNOWN : The uncompressed image buffer returned by the function will use the most optimal pixel format for the file type, and *pixelFormat will contain the ID of this pixel format upon successful return from the function. TJPF_GRAY : Only PGM files and 8-bit BMP files with a grayscale colormap can be loaded. TJPF_CMYK : The RGB or grayscale pixels stored in the file will be converted using a quick & dirty algorithm that is suitable only for testing purposes (proper conversion between CMYK and other formats requires a color management system.) Other pixel formats : The uncompressed image buffer will use the specified pixel format, and pixel format conversion will be performed if necessary.
flags	the bitwise OR of one or more of the flags.

Returns

a pointer to a newly-allocated buffer containing the uncompressed image, converted to the chosen pixel format and with the chosen row alignment, or NULL if an error occurred (see tjGetErrorStr2().) This buffer should be freed using tjFree().

DLLEXPORT int tjPlaneHeight	(	int	componentID,
		int	height,
		int	subsamp
	)

The plane height of a YUV image plane with the given parameters.

Refer to YUV Image Format Notes for a description of plane height.

Parameters

componentID	ID number of the image plane (0 = Y, 1 = U/Cb, 2 = V/Cr)
height	height (in pixels) of the YUV image
subsamp	level of chrominance subsampling in the image (see Chrominance subsampling options.)

Returns

the plane height of a YUV image plane with the given parameters, or -1 if the arguments are out of bounds.

DLLEXPORT unsigned long tjPlaneSizeYUV	(	int	componentID,
		int	width,
		int	stride,
		int	height,
		int	subsamp
	)

The size of the buffer (in bytes) required to hold a YUV image plane with the given parameters.

Parameters

componentID	ID number of the image plane (0 = Y, 1 = U/Cb, 2 = V/Cr)
width	width (in pixels) of the YUV image. NOTE: this is the width of the whole image, not the plane width.
stride	bytes per line in the image plane. Setting this to 0 is the equivalent of setting it to the plane width.
height	height (in pixels) of the YUV image. NOTE: this is the height of the whole image, not the plane height.
subsamp	level of chrominance subsampling in the image (see Chrominance subsampling options.)

Returns

the size of the buffer (in bytes) required to hold the YUV image plane, or -1 if the arguments are out of bounds.

DLLEXPORT int tjPlaneWidth	(	int	componentID,
		int	width,
		int	subsamp
	)

The plane width of a YUV image plane with the given parameters.

Refer to YUV Image Format Notes for a description of plane width.

Parameters

componentID	ID number of the image plane (0 = Y, 1 = U/Cb, 2 = V/Cr)
width	width (in pixels) of the YUV image
subsamp	level of chrominance subsampling in the image (see Chrominance subsampling options.)

Returns

the plane width of a YUV image plane with the given parameters, or -1 if the arguments are out of bounds.

DLLEXPORT int tjSaveImage	(	const char *	filename,
		unsigned char *	buffer,
		int	width,
		int	pitch,
		int	height,
		int	pixelFormat,
		int	flags
	)

Save an uncompressed image from memory to disk.

Parameters

filename	name of a file to which to save the uncompressed image. The image will be stored in Windows BMP or PBMPLUS (PPM/PGM) format, depending on the file extension.
buffer	pointer to an image buffer containing RGB, grayscale, or CMYK pixels to be saved
width	width (in pixels) of the uncompressed image
pitch	bytes per line in the image buffer. Setting this parameter to 0 is the equivalent of setting it to width * tjPixelSize[pixelFormat].
height	height (in pixels) of the uncompressed image
pixelFormat	pixel format of the image buffer (see Pixel formats.) If this parameter is set to TJPF_GRAY, then the image will be stored in PGM or 8-bit (indexed color) BMP format. Otherwise, the image will be stored in PPM or 24-bit BMP format. If this parameter is set to TJPF_CMYK, then the CMYK pixels will be converted to RGB using a quick & dirty algorithm that is suitable only for testing (proper conversion between CMYK and other formats requires a color management system.)
flags	the bitwise OR of one or more of the flags.

Returns

0 if successful, or -1 if an error occurred (see tjGetErrorStr2().)

DLLEXPORT int tjTransform	(	tjhandle	handle,
		const unsigned char *	jpegBuf,
		unsigned long	jpegSize,
		int	n,
		unsigned char **	dstBufs,
		unsigned long *	dstSizes,
		tjtransform *	transforms,
		int	flags
	)

Losslessly transform a JPEG image into another JPEG image.

Lossless transforms work by moving the raw DCT coefficients from one JPEG image structure to another without altering the values of the coefficients. While this is typically faster than decompressing the image, transforming it, and re-compressing it, lossless transforms are not free. Each lossless transform requires reading and performing Huffman decoding on all of the coefficients in the source image, regardless of the size of the destination image. Thus, this function provides a means of generating multiple transformed images from the same source or applying multiple transformations simultaneously, in order to eliminate the need to read the source coefficients multiple times.

Parameters

handle	a handle to a TurboJPEG transformer instance
jpegBuf	pointer to a buffer containing the JPEG source image to transform
jpegSize	size of the JPEG source image (in bytes)
n	the number of transformed JPEG images to generate
dstBufs	pointer to an array of n image buffers. dstBufs[i] will receive a JPEG image that has been transformed using the parameters in transforms[i]. TurboJPEG has the ability to reallocate the JPEG buffer to accommodate the size of the JPEG image. Thus, you can choose to: pre-allocate the JPEG buffer with an arbitrary size using tjAlloc() and let TurboJPEG grow the buffer as needed, set dstBufs[i] to NULL to tell TurboJPEG to allocate the buffer for you, or pre-allocate the buffer to a "worst case" size determined by calling tjBufSize() with the transformed or cropped width and height. Under normal circumstances, this should ensure that the buffer never has to be re-allocated (setting TJFLAG_NOREALLOC guarantees that it won't be.) Note, however, that there are some rare cases (such as transforming images with a large amount of embedded EXIF or ICC profile data) in which the output image will be larger than the worst-case size, and TJFLAG_NOREALLOC cannot be used in those cases. If you choose option 1, dstSizes[i] should be set to the size of your pre-allocated buffer. In any case, unless you have set TJFLAG_NOREALLOC, you should always check dstBufs[i] upon return from this function, as it may have changed.
dstSizes	pointer to an array of n unsigned long variables that will receive the actual sizes (in bytes) of each transformed JPEG image. If dstBufs[i] points to a pre-allocated buffer, then dstSizes[i] should be set to the size of the buffer. Upon return, dstSizes[i] will contain the size of the JPEG image (in bytes.)
transforms	pointer to an array of n tjtransform structures, each of which specifies the transform parameters and/or cropping region for the corresponding transformed output image.
flags	the bitwise OR of one or more of the flags

Returns

0 if successful, or -1 if an error occurred (see tjGetErrorStr2() and tjGetErrorCode().)

Variable Documentation

const int tjAlphaOffset[TJ_NUMPF]

static

Alpha offset (in bytes) for a given pixel format.

This specifies the number of bytes that the Alpha component is offset from the start of the pixel. For instance, if a pixel of format TJ_BGRA is stored in char pixel[], then the alpha component will be pixel[tjAlphaOffset[TJ_BGRA]]. This will be -1 if the pixel format does not have an alpha component.

const int tjBlueOffset[TJ_NUMPF]

static

Blue offset (in bytes) for a given pixel format.

This specifies the number of bytes that the Blue component is offset from the start of the pixel. For instance, if a pixel of format TJ_BGRX is stored in char pixel[], then the blue component will be pixel[tjBlueOffset[TJ_BGRX]]. This will be -1 if the pixel format does not have a blue component.

const int tjGreenOffset[TJ_NUMPF]

static

Green offset (in bytes) for a given pixel format.

This specifies the number of bytes that the green component is offset from the start of the pixel. For instance, if a pixel of format TJ_BGRX is stored in char pixel[], then the green component will be pixel[tjGreenOffset[TJ_BGRX]]. This will be -1 if the pixel format does not have a green component.

const int tjMCUHeight[TJ_NUMSAMP]

static

MCU block height (in pixels) for a given level of chrominance subsampling.

MCU block sizes:

• 8x8 for no subsampling or grayscale
• 16x8 for 4:2:2
• 8x16 for 4:4:0
• 16x16 for 4:2:0
• 32x8 for 4:1:1

const int tjMCUWidth[TJ_NUMSAMP]

static

MCU block width (in pixels) for a given level of chrominance subsampling.

MCU block sizes:

• 8x8 for no subsampling or grayscale
• 16x8 for 4:2:2
• 8x16 for 4:4:0
• 16x16 for 4:2:0
• 32x8 for 4:1:1

const int tjPixelSize[TJ_NUMPF]

static

Pixel size (in bytes) for a given pixel format.

const int tjRedOffset[TJ_NUMPF]

static

Red offset (in bytes) for a given pixel format.

This specifies the number of bytes that the red component is offset from the start of the pixel. For instance, if a pixel of format TJ_BGRX is stored in char pixel[], then the red component will be pixel[tjRedOffset[TJ_BGRX]]. This will be -1 if the pixel format does not have a red component.