1 // Copyright 2022 Google Inc. All Rights Reserved. 2 // 3 // Use of this source code is governed by a BSD-style license 4 // that can be found in the COPYING file in the root of the source 5 // tree. An additional intellectual property rights grant can be found 6 // in the file PATENTS. All contributing project authors may 7 // be found in the AUTHORS file in the root of the source tree. 8 // ----------------------------------------------------------------------------- 9 // 10 // Sharp RGB to YUV conversion. 11 12 #ifndef WEBP_SHARPYUV_SHARPYUV_H_ 13 #define WEBP_SHARPYUV_SHARPYUV_H_ 14 15 #ifdef __cplusplus 16 extern "C" { 17 #endif 18 19 #ifndef SHARPYUV_EXTERN 20 #ifdef WEBP_EXTERN 21 #define SHARPYUV_EXTERN WEBP_EXTERN 22 #else 23 // This explicitly marks library functions and allows for changing the 24 // signature for e.g., Windows DLL builds. 25 #if defined(__GNUC__) && __GNUC__ >= 4 26 #define SHARPYUV_EXTERN extern __attribute__((visibility("default"))) 27 #else 28 #if defined(_MSC_VER) && defined(WEBP_DLL) 29 #define SHARPYUV_EXTERN __declspec(dllexport) 30 #else 31 #define SHARPYUV_EXTERN extern 32 #endif /* _MSC_VER && WEBP_DLL */ 33 #endif /* __GNUC__ >= 4 */ 34 #endif /* WEBP_EXTERN */ 35 #endif /* SHARPYUV_EXTERN */ 36 37 // SharpYUV API version following the convention from semver.org 38 #define SHARPYUV_VERSION_MAJOR 0 39 #define SHARPYUV_VERSION_MINOR 2 40 #define SHARPYUV_VERSION_PATCH 0 41 // Version as a uint32_t. The major number is the high 8 bits. 42 // The minor number is the middle 8 bits. The patch number is the low 16 bits. 43 #define SHARPYUV_MAKE_VERSION(MAJOR, MINOR, PATCH) \ 44 (((MAJOR) << 24) | ((MINOR) << 16) | (PATCH)) 45 #define SHARPYUV_VERSION \ 46 SHARPYUV_MAKE_VERSION(SHARPYUV_VERSION_MAJOR, SHARPYUV_VERSION_MINOR, \ 47 SHARPYUV_VERSION_PATCH) 48 49 // Returns the library's version number, packed in hexadecimal. See 50 // SHARPYUV_VERSION. 51 SHARPYUV_EXTERN int SharpYuvGetVersion(void); 52 53 // RGB to YUV conversion matrix, in 16 bit fixed point. 54 // y = rgb_to_y[0] * r + rgb_to_y[1] * g + rgb_to_y[2] * b + rgb_to_y[3] 55 // u = rgb_to_u[0] * r + rgb_to_u[1] * g + rgb_to_u[2] * b + rgb_to_u[3] 56 // v = rgb_to_v[0] * r + rgb_to_v[1] * g + rgb_to_v[2] * b + rgb_to_v[3] 57 // Then y, u and v values are divided by 1<<16 and rounded. 58 typedef struct { 59 int rgb_to_y[4]; 60 int rgb_to_u[4]; 61 int rgb_to_v[4]; 62 } SharpYuvConversionMatrix; 63 64 // Converts RGB to YUV420 using a downsampling algorithm that minimizes 65 // artefacts caused by chroma subsampling. 66 // This is slower than standard downsampling (averaging of 4 UV values). 67 // Assumes that the image will be upsampled using a bilinear filter. If nearest 68 // neighbor is used instead, the upsampled image might look worse than with 69 // standard downsampling. 70 // r_ptr, g_ptr, b_ptr: pointers to the source r, g and b channels. Should point 71 // to uint8_t buffers if rgb_bit_depth is 8, or uint16_t buffers otherwise. 72 // rgb_step: distance in bytes between two horizontally adjacent pixels on the 73 // r, g and b channels. If rgb_bit_depth is > 8, it should be a 74 // multiple of 2. 75 // rgb_stride: distance in bytes between two vertically adjacent pixels on the 76 // r, g, and b channels. If rgb_bit_depth is > 8, it should be a 77 // multiple of 2. 78 // rgb_bit_depth: number of bits for each r/g/b value. One of: 8, 10, 12, 16. 79 // Note: 16 bit input is truncated to 14 bits before conversion to yuv. 80 // yuv_bit_depth: number of bits for each y/u/v value. One of: 8, 10, 12. 81 // y_ptr, u_ptr, v_ptr: pointers to the destination y, u and v channels. Should 82 // point to uint8_t buffers if yuv_bit_depth is 8, or uint16_t buffers 83 // otherwise. 84 // y_stride, u_stride, v_stride: distance in bytes between two vertically 85 // adjacent pixels on the y, u and v channels. If yuv_bit_depth > 8, they 86 // should be multiples of 2. 87 // width, height: width and height of the image in pixels 88 SHARPYUV_EXTERN int SharpYuvConvert(const void* r_ptr, const void* g_ptr, 89 const void* b_ptr, int rgb_step, 90 int rgb_stride, int rgb_bit_depth, 91 void* y_ptr, int y_stride, void* u_ptr, 92 int u_stride, void* v_ptr, int v_stride, 93 int yuv_bit_depth, int width, int height, 94 const SharpYuvConversionMatrix* yuv_matrix); 95 96 // TODO(b/194336375): Add YUV444 to YUV420 conversion. Maybe also add 422 97 // support (it's rarely used in practice, especially for images). 98 99 #ifdef __cplusplus 100 } // extern "C" 101 #endif 102 103 #endif // WEBP_SHARPYUV_SHARPYUV_H_ 104