xref: /aosp_15_r20/external/webp/src/webp/decode.h (revision b2055c353e87c8814eb2b6b1b11112a1562253bd)
1 // Copyright 2010 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 //  Main decoding functions for WebP images.
11 //
12 // Author: Skal ([email protected])
13 
14 #ifndef WEBP_WEBP_DECODE_H_
15 #define WEBP_WEBP_DECODE_H_
16 
17 #include "./types.h"
18 
19 #ifdef __cplusplus
20 extern "C" {
21 #endif
22 
23 #define WEBP_DECODER_ABI_VERSION 0x0209    // MAJOR(8b) + MINOR(8b)
24 
25 // Note: forward declaring enumerations is not allowed in (strict) C and C++,
26 // the types are left here for reference.
27 // typedef enum VP8StatusCode VP8StatusCode;
28 // typedef enum WEBP_CSP_MODE WEBP_CSP_MODE;
29 typedef struct WebPRGBABuffer WebPRGBABuffer;
30 typedef struct WebPYUVABuffer WebPYUVABuffer;
31 typedef struct WebPDecBuffer WebPDecBuffer;
32 typedef struct WebPIDecoder WebPIDecoder;
33 typedef struct WebPBitstreamFeatures WebPBitstreamFeatures;
34 typedef struct WebPDecoderOptions WebPDecoderOptions;
35 typedef struct WebPDecoderConfig WebPDecoderConfig;
36 
37 // Return the decoder's version number, packed in hexadecimal using 8bits for
38 // each of major/minor/revision. E.g: v2.5.7 is 0x020507.
39 WEBP_EXTERN int WebPGetDecoderVersion(void);
40 
41 // Retrieve basic header information: width, height.
42 // This function will also validate the header, returning true on success,
43 // false otherwise. '*width' and '*height' are only valid on successful return.
44 // Pointers 'width' and 'height' can be passed NULL if deemed irrelevant.
45 // Note: The following chunk sequences (before the raw VP8/VP8L data) are
46 // considered valid by this function:
47 // RIFF + VP8(L)
48 // RIFF + VP8X + (optional chunks) + VP8(L)
49 // ALPH + VP8 <-- Not a valid WebP format: only allowed for internal purpose.
50 // VP8(L)     <-- Not a valid WebP format: only allowed for internal purpose.
51 WEBP_NODISCARD WEBP_EXTERN int WebPGetInfo(
52     const uint8_t* data, size_t data_size, int* width, int* height);
53 
54 // Decodes WebP images pointed to by 'data' and returns RGBA samples, along
55 // with the dimensions in *width and *height. The ordering of samples in
56 // memory is R, G, B, A, R, G, B, A... in scan order (endian-independent).
57 // The returned pointer should be deleted calling WebPFree().
58 // Returns NULL in case of error.
59 WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeRGBA(
60     const uint8_t* data, size_t data_size, int* width, int* height);
61 
62 // Same as WebPDecodeRGBA, but returning A, R, G, B, A, R, G, B... ordered data.
63 WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeARGB(
64     const uint8_t* data, size_t data_size, int* width, int* height);
65 
66 // Same as WebPDecodeRGBA, but returning B, G, R, A, B, G, R, A... ordered data.
67 WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeBGRA(
68     const uint8_t* data, size_t data_size, int* width, int* height);
69 
70 // Same as WebPDecodeRGBA, but returning R, G, B, R, G, B... ordered data.
71 // If the bitstream contains transparency, it is ignored.
72 WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeRGB(
73     const uint8_t* data, size_t data_size, int* width, int* height);
74 
75 // Same as WebPDecodeRGB, but returning B, G, R, B, G, R... ordered data.
76 WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeBGR(
77     const uint8_t* data, size_t data_size, int* width, int* height);
78 
79 // Decode WebP images pointed to by 'data' to Y'UV format(*). The pointer
80 // returned is the Y samples buffer. Upon return, *u and *v will point to
81 // the U and V chroma data. These U and V buffers need NOT be passed to
82 // WebPFree(), unlike the returned Y luma one. The dimension of the U and V
83 // planes are both (*width + 1) / 2 and (*height + 1) / 2.
84 // Upon return, the Y buffer has a stride returned as '*stride', while U and V
85 // have a common stride returned as '*uv_stride'.
86 // 'width' and 'height' may be NULL, the other pointers must not be.
87 // Returns NULL in case of error.
88 // (*) Also named Y'CbCr. See: https://en.wikipedia.org/wiki/YCbCr
89 WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeYUV(
90     const uint8_t* data, size_t data_size, int* width, int* height,
91     uint8_t** u, uint8_t** v, int* stride, int* uv_stride);
92 
93 // These five functions are variants of the above ones, that decode the image
94 // directly into a pre-allocated buffer 'output_buffer'. The maximum storage
95 // available in this buffer is indicated by 'output_buffer_size'. If this
96 // storage is not sufficient (or an error occurred), NULL is returned.
97 // Otherwise, output_buffer is returned, for convenience.
98 // The parameter 'output_stride' specifies the distance (in bytes)
99 // between scanlines. Hence, output_buffer_size is expected to be at least
100 // output_stride x picture-height.
101 WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeRGBAInto(
102     const uint8_t* data, size_t data_size,
103     uint8_t* output_buffer, size_t output_buffer_size, int output_stride);
104 WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeARGBInto(
105     const uint8_t* data, size_t data_size,
106     uint8_t* output_buffer, size_t output_buffer_size, int output_stride);
107 WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeBGRAInto(
108     const uint8_t* data, size_t data_size,
109     uint8_t* output_buffer, size_t output_buffer_size, int output_stride);
110 
111 // RGB and BGR variants. Here too the transparency information, if present,
112 // will be dropped and ignored.
113 WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeRGBInto(
114     const uint8_t* data, size_t data_size,
115     uint8_t* output_buffer, size_t output_buffer_size, int output_stride);
116 WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeBGRInto(
117     const uint8_t* data, size_t data_size,
118     uint8_t* output_buffer, size_t output_buffer_size, int output_stride);
119 
120 // WebPDecodeYUVInto() is a variant of WebPDecodeYUV() that operates directly
121 // into pre-allocated luma/chroma plane buffers. This function requires the
122 // strides to be passed: one for the luma plane and one for each of the
123 // chroma ones. The size of each plane buffer is passed as 'luma_size',
124 // 'u_size' and 'v_size' respectively.
125 // Pointer to the luma plane ('*luma') is returned or NULL if an error occurred
126 // during decoding (or because some buffers were found to be too small).
127 WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPDecodeYUVInto(
128     const uint8_t* data, size_t data_size,
129     uint8_t* luma, size_t luma_size, int luma_stride,
130     uint8_t* u, size_t u_size, int u_stride,
131     uint8_t* v, size_t v_size, int v_stride);
132 
133 //------------------------------------------------------------------------------
134 // Output colorspaces and buffer
135 
136 // Colorspaces
137 // Note: the naming describes the byte-ordering of packed samples in memory.
138 // For instance, MODE_BGRA relates to samples ordered as B,G,R,A,B,G,R,A,...
139 // Non-capital names (e.g.:MODE_Argb) relates to pre-multiplied RGB channels.
140 // RGBA-4444 and RGB-565 colorspaces are represented by following byte-order:
141 // RGBA-4444: [r3 r2 r1 r0 g3 g2 g1 g0], [b3 b2 b1 b0 a3 a2 a1 a0], ...
142 // RGB-565: [r4 r3 r2 r1 r0 g5 g4 g3], [g2 g1 g0 b4 b3 b2 b1 b0], ...
143 // In the case WEBP_SWAP_16BITS_CSP is defined, the bytes are swapped for
144 // these two modes:
145 // RGBA-4444: [b3 b2 b1 b0 a3 a2 a1 a0], [r3 r2 r1 r0 g3 g2 g1 g0], ...
146 // RGB-565: [g2 g1 g0 b4 b3 b2 b1 b0], [r4 r3 r2 r1 r0 g5 g4 g3], ...
147 
148 typedef enum WEBP_CSP_MODE {
149   MODE_RGB = 0, MODE_RGBA = 1,
150   MODE_BGR = 2, MODE_BGRA = 3,
151   MODE_ARGB = 4, MODE_RGBA_4444 = 5,
152   MODE_RGB_565 = 6,
153   // RGB-premultiplied transparent modes (alpha value is preserved)
154   MODE_rgbA = 7,
155   MODE_bgrA = 8,
156   MODE_Argb = 9,
157   MODE_rgbA_4444 = 10,
158   // YUV modes must come after RGB ones.
159   MODE_YUV = 11, MODE_YUVA = 12,  // yuv 4:2:0
160   MODE_LAST = 13
161 } WEBP_CSP_MODE;
162 
163 // Some useful macros:
WebPIsPremultipliedMode(WEBP_CSP_MODE mode)164 static WEBP_INLINE int WebPIsPremultipliedMode(WEBP_CSP_MODE mode) {
165   return (mode == MODE_rgbA || mode == MODE_bgrA || mode == MODE_Argb ||
166           mode == MODE_rgbA_4444);
167 }
168 
WebPIsAlphaMode(WEBP_CSP_MODE mode)169 static WEBP_INLINE int WebPIsAlphaMode(WEBP_CSP_MODE mode) {
170   return (mode == MODE_RGBA || mode == MODE_BGRA || mode == MODE_ARGB ||
171           mode == MODE_RGBA_4444 || mode == MODE_YUVA ||
172           WebPIsPremultipliedMode(mode));
173 }
174 
WebPIsRGBMode(WEBP_CSP_MODE mode)175 static WEBP_INLINE int WebPIsRGBMode(WEBP_CSP_MODE mode) {
176   return (mode < MODE_YUV);
177 }
178 
179 //------------------------------------------------------------------------------
180 // WebPDecBuffer: Generic structure for describing the output sample buffer.
181 
182 struct WebPRGBABuffer {    // view as RGBA
183   uint8_t* rgba;    // pointer to RGBA samples
184   int stride;       // stride in bytes from one scanline to the next.
185   size_t size;      // total size of the *rgba buffer.
186 };
187 
188 struct WebPYUVABuffer {              // view as YUVA
189   uint8_t* y, *u, *v, *a;     // pointer to luma, chroma U/V, alpha samples
190   int y_stride;               // luma stride
191   int u_stride, v_stride;     // chroma strides
192   int a_stride;               // alpha stride
193   size_t y_size;              // luma plane size
194   size_t u_size, v_size;      // chroma planes size
195   size_t a_size;              // alpha-plane size
196 };
197 
198 // Output buffer
199 struct WebPDecBuffer {
200   WEBP_CSP_MODE colorspace;  // Colorspace.
201   int width, height;         // Dimensions.
202   int is_external_memory;    // If non-zero, 'internal_memory' pointer is not
203                              // used. If value is '2' or more, the external
204                              // memory is considered 'slow' and multiple
205                              // read/write will be avoided.
206   union {
207     WebPRGBABuffer RGBA;
208     WebPYUVABuffer YUVA;
209   } u;                       // Nameless union of buffer parameters.
210   uint32_t       pad[4];     // padding for later use
211 
212   uint8_t* private_memory;   // Internally allocated memory (only when
213                              // is_external_memory is 0). Should not be used
214                              // externally, but accessed via the buffer union.
215 };
216 
217 // Internal, version-checked, entry point
218 WEBP_NODISCARD WEBP_EXTERN int WebPInitDecBufferInternal(WebPDecBuffer*, int);
219 
220 // Initialize the structure as empty. Must be called before any other use.
221 // Returns false in case of version mismatch
WebPInitDecBuffer(WebPDecBuffer * buffer)222 WEBP_NODISCARD static WEBP_INLINE int WebPInitDecBuffer(WebPDecBuffer* buffer) {
223   return WebPInitDecBufferInternal(buffer, WEBP_DECODER_ABI_VERSION);
224 }
225 
226 // Free any memory associated with the buffer. Must always be called last.
227 // Note: doesn't free the 'buffer' structure itself.
228 WEBP_EXTERN void WebPFreeDecBuffer(WebPDecBuffer* buffer);
229 
230 //------------------------------------------------------------------------------
231 // Enumeration of the status codes
232 
233 typedef enum WEBP_NODISCARD VP8StatusCode {
234   VP8_STATUS_OK = 0,
235   VP8_STATUS_OUT_OF_MEMORY,
236   VP8_STATUS_INVALID_PARAM,
237   VP8_STATUS_BITSTREAM_ERROR,
238   VP8_STATUS_UNSUPPORTED_FEATURE,
239   VP8_STATUS_SUSPENDED,
240   VP8_STATUS_USER_ABORT,
241   VP8_STATUS_NOT_ENOUGH_DATA
242 } VP8StatusCode;
243 
244 //------------------------------------------------------------------------------
245 // Incremental decoding
246 //
247 // This API allows streamlined decoding of partial data.
248 // Picture can be incrementally decoded as data become available thanks to the
249 // WebPIDecoder object. This object can be left in a SUSPENDED state if the
250 // picture is only partially decoded, pending additional input.
251 // Code example:
252 /*
253      WebPInitDecBuffer(&output_buffer);
254      output_buffer.colorspace = mode;
255      ...
256      WebPIDecoder* idec = WebPINewDecoder(&output_buffer);
257      while (additional_data_is_available) {
258        // ... (get additional data in some new_data[] buffer)
259        status = WebPIAppend(idec, new_data, new_data_size);
260        if (status != VP8_STATUS_OK && status != VP8_STATUS_SUSPENDED) {
261          break;    // an error occurred.
262        }
263 
264        // The above call decodes the current available buffer.
265        // Part of the image can now be refreshed by calling
266        // WebPIDecGetRGB()/WebPIDecGetYUVA() etc.
267      }
268      WebPIDelete(idec);
269 */
270 
271 // Creates a new incremental decoder with the supplied buffer parameter.
272 // This output_buffer can be passed NULL, in which case a default output buffer
273 // is used (with MODE_RGB). Otherwise, an internal reference to 'output_buffer'
274 // is kept, which means that the lifespan of 'output_buffer' must be larger than
275 // that of the returned WebPIDecoder object.
276 // The supplied 'output_buffer' content MUST NOT be changed between calls to
277 // WebPIAppend() or WebPIUpdate() unless 'output_buffer.is_external_memory' is
278 // not set to 0. In such a case, it is allowed to modify the pointers, size and
279 // stride of output_buffer.u.RGBA or output_buffer.u.YUVA, provided they remain
280 // within valid bounds.
281 // All other fields of WebPDecBuffer MUST remain constant between calls.
282 // Returns NULL if the allocation failed.
283 WEBP_NODISCARD WEBP_EXTERN WebPIDecoder* WebPINewDecoder(
284     WebPDecBuffer* output_buffer);
285 
286 // This function allocates and initializes an incremental-decoder object, which
287 // will output the RGB/A samples specified by 'csp' into a preallocated
288 // buffer 'output_buffer'. The size of this buffer is at least
289 // 'output_buffer_size' and the stride (distance in bytes between two scanlines)
290 // is specified by 'output_stride'.
291 // Additionally, output_buffer can be passed NULL in which case the output
292 // buffer will be allocated automatically when the decoding starts. The
293 // colorspace 'csp' is taken into account for allocating this buffer. All other
294 // parameters are ignored.
295 // Returns NULL if the allocation failed, or if some parameters are invalid.
296 WEBP_NODISCARD WEBP_EXTERN WebPIDecoder* WebPINewRGB(
297     WEBP_CSP_MODE csp,
298     uint8_t* output_buffer, size_t output_buffer_size, int output_stride);
299 
300 // This function allocates and initializes an incremental-decoder object, which
301 // will output the raw luma/chroma samples into a preallocated planes if
302 // supplied. The luma plane is specified by its pointer 'luma', its size
303 // 'luma_size' and its stride 'luma_stride'. Similarly, the chroma-u plane
304 // is specified by the 'u', 'u_size' and 'u_stride' parameters, and the chroma-v
305 // plane by 'v' and 'v_size'. And same for the alpha-plane. The 'a' pointer
306 // can be pass NULL in case one is not interested in the transparency plane.
307 // Conversely, 'luma' can be passed NULL if no preallocated planes are supplied.
308 // In this case, the output buffer will be automatically allocated (using
309 // MODE_YUVA) when decoding starts. All parameters are then ignored.
310 // Returns NULL if the allocation failed or if a parameter is invalid.
311 WEBP_NODISCARD WEBP_EXTERN WebPIDecoder* WebPINewYUVA(
312     uint8_t* luma, size_t luma_size, int luma_stride,
313     uint8_t* u, size_t u_size, int u_stride,
314     uint8_t* v, size_t v_size, int v_stride,
315     uint8_t* a, size_t a_size, int a_stride);
316 
317 // Deprecated version of the above, without the alpha plane.
318 // Kept for backward compatibility.
319 WEBP_NODISCARD WEBP_EXTERN WebPIDecoder* WebPINewYUV(
320     uint8_t* luma, size_t luma_size, int luma_stride,
321     uint8_t* u, size_t u_size, int u_stride,
322     uint8_t* v, size_t v_size, int v_stride);
323 
324 // Deletes the WebPIDecoder object and associated memory. Must always be called
325 // if WebPINewDecoder, WebPINewRGB or WebPINewYUV succeeded.
326 WEBP_EXTERN void WebPIDelete(WebPIDecoder* idec);
327 
328 // Copies and decodes the next available data. Returns VP8_STATUS_OK when
329 // the image is successfully decoded. Returns VP8_STATUS_SUSPENDED when more
330 // data is expected. Returns error in other cases.
331 WEBP_EXTERN VP8StatusCode WebPIAppend(
332     WebPIDecoder* idec, const uint8_t* data, size_t data_size);
333 
334 // A variant of the above function to be used when data buffer contains
335 // partial data from the beginning. In this case data buffer is not copied
336 // to the internal memory.
337 // Note that the value of the 'data' pointer can change between calls to
338 // WebPIUpdate, for instance when the data buffer is resized to fit larger data.
339 WEBP_EXTERN VP8StatusCode WebPIUpdate(
340     WebPIDecoder* idec, const uint8_t* data, size_t data_size);
341 
342 // Returns the RGB/A image decoded so far. Returns NULL if output params
343 // are not initialized yet. The RGB/A output type corresponds to the colorspace
344 // specified during call to WebPINewDecoder() or WebPINewRGB().
345 // *last_y is the index of last decoded row in raster scan order. Some pointers
346 // (*last_y, *width etc.) can be NULL if corresponding information is not
347 // needed. The values in these pointers are only valid on successful (non-NULL)
348 // return.
349 WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPIDecGetRGB(
350     const WebPIDecoder* idec, int* last_y,
351     int* width, int* height, int* stride);
352 
353 // Same as above function to get a YUVA image. Returns pointer to the luma
354 // plane or NULL in case of error. If there is no alpha information
355 // the alpha pointer '*a' will be returned NULL.
356 WEBP_NODISCARD WEBP_EXTERN uint8_t* WebPIDecGetYUVA(
357     const WebPIDecoder* idec, int* last_y,
358     uint8_t** u, uint8_t** v, uint8_t** a,
359     int* width, int* height, int* stride, int* uv_stride, int* a_stride);
360 
361 // Deprecated alpha-less version of WebPIDecGetYUVA(): it will ignore the
362 // alpha information (if present). Kept for backward compatibility.
WebPIDecGetYUV(const WebPIDecoder * idec,int * last_y,uint8_t ** u,uint8_t ** v,int * width,int * height,int * stride,int * uv_stride)363 WEBP_NODISCARD static WEBP_INLINE uint8_t* WebPIDecGetYUV(
364     const WebPIDecoder* idec, int* last_y, uint8_t** u, uint8_t** v,
365     int* width, int* height, int* stride, int* uv_stride) {
366   return WebPIDecGetYUVA(idec, last_y, u, v, NULL, width, height,
367                          stride, uv_stride, NULL);
368 }
369 
370 // Generic call to retrieve information about the displayable area.
371 // If non NULL, the left/right/width/height pointers are filled with the visible
372 // rectangular area so far.
373 // Returns NULL in case the incremental decoder object is in an invalid state.
374 // Otherwise returns the pointer to the internal representation. This structure
375 // is read-only, tied to WebPIDecoder's lifespan and should not be modified.
376 WEBP_NODISCARD WEBP_EXTERN const WebPDecBuffer* WebPIDecodedArea(
377     const WebPIDecoder* idec, int* left, int* top, int* width, int* height);
378 
379 //------------------------------------------------------------------------------
380 // Advanced decoding parametrization
381 //
382 //  Code sample for using the advanced decoding API
383 /*
384      // A) Init a configuration object
385      WebPDecoderConfig config;
386      CHECK(WebPInitDecoderConfig(&config));
387 
388      // B) optional: retrieve the bitstream's features.
389      CHECK(WebPGetFeatures(data, data_size, &config.input) == VP8_STATUS_OK);
390 
391      // C) Adjust 'config', if needed
392      config.options.no_fancy_upsampling = 1;
393      config.output.colorspace = MODE_BGRA;
394      // etc.
395 
396      // Note that you can also make config.output point to an externally
397      // supplied memory buffer, provided it's big enough to store the decoded
398      // picture. Otherwise, config.output will just be used to allocate memory
399      // and store the decoded picture.
400 
401      // D) Decode!
402      CHECK(WebPDecode(data, data_size, &config) == VP8_STATUS_OK);
403 
404      // E) Decoded image is now in config.output (and config.output.u.RGBA)
405 
406      // F) Reclaim memory allocated in config's object. It's safe to call
407      // this function even if the memory is external and wasn't allocated
408      // by WebPDecode().
409      WebPFreeDecBuffer(&config.output);
410 */
411 
412 // Features gathered from the bitstream
413 struct WebPBitstreamFeatures {
414   int width;          // Width in pixels, as read from the bitstream.
415   int height;         // Height in pixels, as read from the bitstream.
416   int has_alpha;      // True if the bitstream contains an alpha channel.
417   int has_animation;  // True if the bitstream is an animation.
418   int format;         // 0 = undefined (/mixed), 1 = lossy, 2 = lossless
419 
420   uint32_t pad[5];    // padding for later use
421 };
422 
423 // Internal, version-checked, entry point
424 WEBP_EXTERN VP8StatusCode WebPGetFeaturesInternal(
425     const uint8_t*, size_t, WebPBitstreamFeatures*, int);
426 
427 // Retrieve features from the bitstream. The *features structure is filled
428 // with information gathered from the bitstream.
429 // Returns VP8_STATUS_OK when the features are successfully retrieved. Returns
430 // VP8_STATUS_NOT_ENOUGH_DATA when more data is needed to retrieve the
431 // features from headers. Returns error in other cases.
432 // Note: The following chunk sequences (before the raw VP8/VP8L data) are
433 // considered valid by this function:
434 // RIFF + VP8(L)
435 // RIFF + VP8X + (optional chunks) + VP8(L)
436 // ALPH + VP8 <-- Not a valid WebP format: only allowed for internal purpose.
437 // VP8(L)     <-- Not a valid WebP format: only allowed for internal purpose.
WebPGetFeatures(const uint8_t * data,size_t data_size,WebPBitstreamFeatures * features)438 static WEBP_INLINE VP8StatusCode WebPGetFeatures(
439     const uint8_t* data, size_t data_size,
440     WebPBitstreamFeatures* features) {
441   return WebPGetFeaturesInternal(data, data_size, features,
442                                  WEBP_DECODER_ABI_VERSION);
443 }
444 
445 // Decoding options
446 struct WebPDecoderOptions {
447   int bypass_filtering;               // if true, skip the in-loop filtering
448   int no_fancy_upsampling;            // if true, use faster pointwise upsampler
449   int use_cropping;                   // if true, cropping is applied _first_
450   int crop_left, crop_top;            // top-left position for cropping.
451                                       // Will be snapped to even values.
452   int crop_width, crop_height;        // dimension of the cropping area
453   int use_scaling;                    // if true, scaling is applied _afterward_
454   int scaled_width, scaled_height;    // final resolution
455   int use_threads;                    // if true, use multi-threaded decoding
456   int dithering_strength;             // dithering strength (0=Off, 100=full)
457   int flip;                           // if true, flip output vertically
458   int alpha_dithering_strength;       // alpha dithering strength in [0..100]
459 
460   uint32_t pad[5];                    // padding for later use
461 };
462 
463 // Main object storing the configuration for advanced decoding.
464 struct WebPDecoderConfig {
465   WebPBitstreamFeatures input;  // Immutable bitstream features (optional)
466   WebPDecBuffer output;         // Output buffer (can point to external mem)
467   WebPDecoderOptions options;   // Decoding options
468 };
469 
470 // Internal, version-checked, entry point
471 WEBP_NODISCARD WEBP_EXTERN int WebPInitDecoderConfigInternal(WebPDecoderConfig*,
472                                                              int);
473 
474 // Initialize the configuration as empty. This function must always be
475 // called first, unless WebPGetFeatures() is to be called.
476 // Returns false in case of mismatched version.
WebPInitDecoderConfig(WebPDecoderConfig * config)477 WEBP_NODISCARD static WEBP_INLINE int WebPInitDecoderConfig(
478     WebPDecoderConfig* config) {
479   return WebPInitDecoderConfigInternal(config, WEBP_DECODER_ABI_VERSION);
480 }
481 
482 // Instantiate a new incremental decoder object with the requested
483 // configuration. The bitstream can be passed using 'data' and 'data_size'
484 // parameter, in which case the features will be parsed and stored into
485 // config->input. Otherwise, 'data' can be NULL and no parsing will occur.
486 // Note that 'config' can be NULL too, in which case a default configuration
487 // is used. If 'config' is not NULL, it must outlive the WebPIDecoder object
488 // as some references to its fields will be used. No internal copy of 'config'
489 // is made.
490 // The return WebPIDecoder object must always be deleted calling WebPIDelete().
491 // Returns NULL in case of error (and config->status will then reflect
492 // the error condition, if available).
493 WEBP_NODISCARD WEBP_EXTERN WebPIDecoder* WebPIDecode(
494     const uint8_t* data, size_t data_size, WebPDecoderConfig* config);
495 
496 // Non-incremental version. This version decodes the full data at once, taking
497 // 'config' into account. Returns decoding status (which should be VP8_STATUS_OK
498 // if the decoding was successful). Note that 'config' cannot be NULL.
499 WEBP_EXTERN VP8StatusCode WebPDecode(const uint8_t* data, size_t data_size,
500                                      WebPDecoderConfig* config);
501 
502 #ifdef __cplusplus
503 }    // extern "C"
504 #endif
505 
506 #endif  // WEBP_WEBP_DECODE_H_
507