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1 // Copyright 2011 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 // Internal header: WebP decoding parameters and custom IO on buffer
11 //
12 // Author: somnath@google.com (Somnath Banerjee)
13 
14 #ifndef WEBP_DEC_WEBPI_DEC_H_
15 #define WEBP_DEC_WEBPI_DEC_H_
16 
17 #ifdef __cplusplus
18 extern "C" {
19 #endif
20 
21 #include "src/utils/rescaler_utils.h"
22 #include "src/dec/vp8_dec.h"
23 
24 //------------------------------------------------------------------------------
25 // WebPDecParams: Decoding output parameters. Transient internal object.
26 
27 typedef struct WebPDecParams WebPDecParams;
28 typedef int (*OutputFunc)(const VP8Io* const io, WebPDecParams* const p);
29 typedef int (*OutputAlphaFunc)(const VP8Io* const io, WebPDecParams* const p,
30                                int expected_num_out_lines);
31 typedef int (*OutputRowFunc)(WebPDecParams* const p, int y_pos,
32                              int max_out_lines);
33 
34 struct WebPDecParams {
35   WebPDecBuffer* output;             // output buffer.
36   uint8_t* tmp_y, *tmp_u, *tmp_v;    // cache for the fancy upsampler
37                                      // or used for tmp rescaling
38 
39   int last_y;                 // coordinate of the line that was last output
40   const WebPDecoderOptions* options;  // if not NULL, use alt decoding features
41 
42   WebPRescaler* scaler_y, *scaler_u, *scaler_v, *scaler_a;  // rescalers
43   void* memory;                  // overall scratch memory for the output work.
44 
45   OutputFunc emit;               // output RGB or YUV samples
46   OutputAlphaFunc emit_alpha;    // output alpha channel
47   OutputRowFunc emit_alpha_row;  // output one line of rescaled alpha values
48 };
49 
50 // Should be called first, before any use of the WebPDecParams object.
51 void WebPResetDecParams(WebPDecParams* const params);
52 
53 //------------------------------------------------------------------------------
54 // Header parsing helpers
55 
56 // Structure storing a description of the RIFF headers.
57 typedef struct {
58   const uint8_t* data;         // input buffer
59   size_t data_size;            // input buffer size
60   int have_all_data;           // true if all data is known to be available
61   size_t offset;               // offset to main data chunk (VP8 or VP8L)
62   const uint8_t* alpha_data;   // points to alpha chunk (if present)
63   size_t alpha_data_size;      // alpha chunk size
64   size_t compressed_size;      // VP8/VP8L compressed data size
65   size_t riff_size;            // size of the riff payload (or 0 if absent)
66   int is_lossless;             // true if a VP8L chunk is present
67 } WebPHeaderStructure;
68 
69 // Skips over all valid chunks prior to the first VP8/VP8L frame header.
70 // Returns: VP8_STATUS_OK, VP8_STATUS_BITSTREAM_ERROR (invalid header/chunk),
71 // VP8_STATUS_NOT_ENOUGH_DATA (partial input) or VP8_STATUS_UNSUPPORTED_FEATURE
72 // in the case of non-decodable features (animation for instance).
73 // In 'headers', compressed_size, offset, alpha_data, alpha_size, and lossless
74 // fields are updated appropriately upon success.
75 VP8StatusCode WebPParseHeaders(WebPHeaderStructure* const headers);
76 
77 //------------------------------------------------------------------------------
78 // Misc utils
79 
80 // Initializes VP8Io with custom setup, io and teardown functions. The default
81 // hooks will use the supplied 'params' as io->opaque handle.
82 void WebPInitCustomIo(WebPDecParams* const params, VP8Io* const io);
83 
84 // Setup crop_xxx fields, mb_w and mb_h in io. 'src_colorspace' refers
85 // to the *compressed* format, not the output one.
86 int WebPIoInitFromOptions(const WebPDecoderOptions* const options,
87                           VP8Io* const io, WEBP_CSP_MODE src_colorspace);
88 
89 //------------------------------------------------------------------------------
90 // Internal functions regarding WebPDecBuffer memory (in buffer.c).
91 // Don't really need to be externally visible for now.
92 
93 // Prepare 'buffer' with the requested initial dimensions width/height.
94 // If no external storage is supplied, initializes buffer by allocating output
95 // memory and setting up the stride information. Validate the parameters. Return
96 // an error code in case of problem (no memory, or invalid stride / size /
97 // dimension / etc.). If *options is not NULL, also verify that the options'
98 // parameters are valid and apply them to the width/height dimensions of the
99 // output buffer. This takes cropping / scaling / rotation into account.
100 // Also incorporates the options->flip flag to flip the buffer parameters if
101 // needed.
102 VP8StatusCode WebPAllocateDecBuffer(int width, int height,
103                                     const WebPDecoderOptions* const options,
104                                     WebPDecBuffer* const buffer);
105 
106 // Flip buffer vertically by negating the various strides.
107 VP8StatusCode WebPFlipBuffer(WebPDecBuffer* const buffer);
108 
109 // Copy 'src' into 'dst' buffer, making sure 'dst' is not marked as owner of the
110 // memory (still held by 'src'). No pixels are copied.
111 void WebPCopyDecBuffer(const WebPDecBuffer* const src,
112                        WebPDecBuffer* const dst);
113 
114 // Copy and transfer ownership from src to dst (beware of parameter order!)
115 void WebPGrabDecBuffer(WebPDecBuffer* const src, WebPDecBuffer* const dst);
116 
117 // Copy pixels from 'src' into a *preallocated* 'dst' buffer. Returns
118 // VP8_STATUS_INVALID_PARAM if the 'dst' is not set up correctly for the copy.
119 VP8StatusCode WebPCopyDecBufferPixels(const WebPDecBuffer* const src,
120                                       WebPDecBuffer* const dst);
121 
122 // Returns true if decoding will be slow with the current configuration
123 // and bitstream features.
124 int WebPAvoidSlowMemory(const WebPDecBuffer* const output,
125                         const WebPBitstreamFeatures* const features);
126 
127 //------------------------------------------------------------------------------
128 
129 #ifdef __cplusplus
130 }    // extern "C"
131 #endif
132 
133 #endif  // WEBP_DEC_WEBPI_DEC_H_
134