encode.h 26 KB

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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. // WebP encoder: main interface
  11. //
  12. // Author: Skal (pascal.massimino@gmail.com)
  13. #ifndef WEBP_WEBP_ENCODE_H_
  14. #define WEBP_WEBP_ENCODE_H_
  15. #include "./types.h"
  16. #ifdef __cplusplus
  17. extern "C" {
  18. #endif
  19. #define WEBP_ENCODER_ABI_VERSION 0x0209 // MAJOR(8b) + MINOR(8b)
  20. // Note: forward declaring enumerations is not allowed in (strict) C and C++,
  21. // the types are left here for reference.
  22. // typedef enum WebPImageHint WebPImageHint;
  23. // typedef enum WebPEncCSP WebPEncCSP;
  24. // typedef enum WebPPreset WebPPreset;
  25. // typedef enum WebPEncodingError WebPEncodingError;
  26. typedef struct WebPConfig WebPConfig;
  27. typedef struct WebPPicture WebPPicture; // main structure for I/O
  28. typedef struct WebPAuxStats WebPAuxStats;
  29. typedef struct WebPMemoryWriter WebPMemoryWriter;
  30. // Return the encoder's version number, packed in hexadecimal using 8bits for
  31. // each of major/minor/revision. E.g: v2.5.7 is 0x020507.
  32. WEBP_EXTERN(int) WebPGetEncoderVersion(void);
  33. //------------------------------------------------------------------------------
  34. // One-stop-shop call! No questions asked:
  35. // Returns the size of the compressed data (pointed to by *output), or 0 if
  36. // an error occurred. The compressed data must be released by the caller
  37. // using the call 'WebPFree(*output)'.
  38. // These functions compress using the lossy format, and the quality_factor
  39. // can go from 0 (smaller output, lower quality) to 100 (best quality,
  40. // larger output).
  41. WEBP_EXTERN(size_t) WebPEncodeRGB(const uint8_t* rgb,
  42. int width, int height, int stride,
  43. float quality_factor, uint8_t** output);
  44. WEBP_EXTERN(size_t) WebPEncodeBGR(const uint8_t* bgr,
  45. int width, int height, int stride,
  46. float quality_factor, uint8_t** output);
  47. WEBP_EXTERN(size_t) WebPEncodeRGBA(const uint8_t* rgba,
  48. int width, int height, int stride,
  49. float quality_factor, uint8_t** output);
  50. WEBP_EXTERN(size_t) WebPEncodeBGRA(const uint8_t* bgra,
  51. int width, int height, int stride,
  52. float quality_factor, uint8_t** output);
  53. // These functions are the equivalent of the above, but compressing in a
  54. // lossless manner. Files are usually larger than lossy format, but will
  55. // not suffer any compression loss.
  56. WEBP_EXTERN(size_t) WebPEncodeLosslessRGB(const uint8_t* rgb,
  57. int width, int height, int stride,
  58. uint8_t** output);
  59. WEBP_EXTERN(size_t) WebPEncodeLosslessBGR(const uint8_t* bgr,
  60. int width, int height, int stride,
  61. uint8_t** output);
  62. WEBP_EXTERN(size_t) WebPEncodeLosslessRGBA(const uint8_t* rgba,
  63. int width, int height, int stride,
  64. uint8_t** output);
  65. WEBP_EXTERN(size_t) WebPEncodeLosslessBGRA(const uint8_t* bgra,
  66. int width, int height, int stride,
  67. uint8_t** output);
  68. // Releases memory returned by the WebPEncode*() functions above.
  69. WEBP_EXTERN(void) WebPFree(void* ptr);
  70. //------------------------------------------------------------------------------
  71. // Coding parameters
  72. // Image characteristics hint for the underlying encoder.
  73. typedef enum WebPImageHint {
  74. WEBP_HINT_DEFAULT = 0, // default preset.
  75. WEBP_HINT_PICTURE, // digital picture, like portrait, inner shot
  76. WEBP_HINT_PHOTO, // outdoor photograph, with natural lighting
  77. WEBP_HINT_GRAPH, // Discrete tone image (graph, map-tile etc).
  78. WEBP_HINT_LAST
  79. } WebPImageHint;
  80. // Compression parameters.
  81. struct WebPConfig {
  82. int lossless; // Lossless encoding (0=lossy(default), 1=lossless).
  83. float quality; // between 0 (smallest file) and 100 (biggest)
  84. int method; // quality/speed trade-off (0=fast, 6=slower-better)
  85. WebPImageHint image_hint; // Hint for image type (lossless only for now).
  86. // Parameters related to lossy compression only:
  87. int target_size; // if non-zero, set the desired target size in bytes.
  88. // Takes precedence over the 'compression' parameter.
  89. float target_PSNR; // if non-zero, specifies the minimal distortion to
  90. // try to achieve. Takes precedence over target_size.
  91. int segments; // maximum number of segments to use, in [1..4]
  92. int sns_strength; // Spatial Noise Shaping. 0=off, 100=maximum.
  93. int filter_strength; // range: [0 = off .. 100 = strongest]
  94. int filter_sharpness; // range: [0 = off .. 7 = least sharp]
  95. int filter_type; // filtering type: 0 = simple, 1 = strong (only used
  96. // if filter_strength > 0 or autofilter > 0)
  97. int autofilter; // Auto adjust filter's strength [0 = off, 1 = on]
  98. int alpha_compression; // Algorithm for encoding the alpha plane (0 = none,
  99. // 1 = compressed with WebP lossless). Default is 1.
  100. int alpha_filtering; // Predictive filtering method for alpha plane.
  101. // 0: none, 1: fast, 2: best. Default if 1.
  102. int alpha_quality; // Between 0 (smallest size) and 100 (lossless).
  103. // Default is 100.
  104. int pass; // number of entropy-analysis passes (in [1..10]).
  105. int show_compressed; // if true, export the compressed picture back.
  106. // In-loop filtering is not applied.
  107. int preprocessing; // preprocessing filter:
  108. // 0=none, 1=segment-smooth, 2=pseudo-random dithering
  109. int partitions; // log2(number of token partitions) in [0..3]. Default
  110. // is set to 0 for easier progressive decoding.
  111. int partition_limit; // quality degradation allowed to fit the 512k limit
  112. // on prediction modes coding (0: no degradation,
  113. // 100: maximum possible degradation).
  114. int emulate_jpeg_size; // If true, compression parameters will be remapped
  115. // to better match the expected output size from
  116. // JPEG compression. Generally, the output size will
  117. // be similar but the degradation will be lower.
  118. int thread_level; // If non-zero, try and use multi-threaded encoding.
  119. int low_memory; // If set, reduce memory usage (but increase CPU use).
  120. int near_lossless; // Near lossless encoding [0 = off(default) .. 100].
  121. // This feature is experimental.
  122. int exact; // if non-zero, preserve the exact RGB values under
  123. // transparent area. Otherwise, discard this invisible
  124. // RGB information for better compression. The default
  125. // value is 0.
  126. #ifdef WEBP_EXPERIMENTAL_FEATURES
  127. int delta_palettization;
  128. uint32_t pad[2]; // padding for later use
  129. #else
  130. uint32_t pad[3]; // padding for later use
  131. #endif // WEBP_EXPERIMENTAL_FEATURES
  132. };
  133. // Enumerate some predefined settings for WebPConfig, depending on the type
  134. // of source picture. These presets are used when calling WebPConfigPreset().
  135. typedef enum WebPPreset {
  136. WEBP_PRESET_DEFAULT = 0, // default preset.
  137. WEBP_PRESET_PICTURE, // digital picture, like portrait, inner shot
  138. WEBP_PRESET_PHOTO, // outdoor photograph, with natural lighting
  139. WEBP_PRESET_DRAWING, // hand or line drawing, with high-contrast details
  140. WEBP_PRESET_ICON, // small-sized colorful images
  141. WEBP_PRESET_TEXT // text-like
  142. } WebPPreset;
  143. // Internal, version-checked, entry point
  144. WEBP_EXTERN(int) WebPConfigInitInternal(WebPConfig*, WebPPreset, float, int);
  145. // Should always be called, to initialize a fresh WebPConfig structure before
  146. // modification. Returns false in case of version mismatch. WebPConfigInit()
  147. // must have succeeded before using the 'config' object.
  148. // Note that the default values are lossless=0 and quality=75.
  149. static WEBP_INLINE int WebPConfigInit(WebPConfig* config) {
  150. return WebPConfigInitInternal(config, WEBP_PRESET_DEFAULT, 75.f,
  151. WEBP_ENCODER_ABI_VERSION);
  152. }
  153. // This function will initialize the configuration according to a predefined
  154. // set of parameters (referred to by 'preset') and a given quality factor.
  155. // This function can be called as a replacement to WebPConfigInit(). Will
  156. // return false in case of error.
  157. static WEBP_INLINE int WebPConfigPreset(WebPConfig* config,
  158. WebPPreset preset, float quality) {
  159. return WebPConfigInitInternal(config, preset, quality,
  160. WEBP_ENCODER_ABI_VERSION);
  161. }
  162. // Activate the lossless compression mode with the desired efficiency level
  163. // between 0 (fastest, lowest compression) and 9 (slower, best compression).
  164. // A good default level is '6', providing a fair tradeoff between compression
  165. // speed and final compressed size.
  166. // This function will overwrite several fields from config: 'method', 'quality'
  167. // and 'lossless'. Returns false in case of parameter error.
  168. WEBP_EXTERN(int) WebPConfigLosslessPreset(WebPConfig* config, int level);
  169. // Returns true if 'config' is non-NULL and all configuration parameters are
  170. // within their valid ranges.
  171. WEBP_EXTERN(int) WebPValidateConfig(const WebPConfig* config);
  172. //------------------------------------------------------------------------------
  173. // Input / Output
  174. // Structure for storing auxiliary statistics (mostly for lossy encoding).
  175. struct WebPAuxStats {
  176. int coded_size; // final size
  177. float PSNR[5]; // peak-signal-to-noise ratio for Y/U/V/All/Alpha
  178. int block_count[3]; // number of intra4/intra16/skipped macroblocks
  179. int header_bytes[2]; // approximate number of bytes spent for header
  180. // and mode-partition #0
  181. int residual_bytes[3][4]; // approximate number of bytes spent for
  182. // DC/AC/uv coefficients for each (0..3) segments.
  183. int segment_size[4]; // number of macroblocks in each segments
  184. int segment_quant[4]; // quantizer values for each segments
  185. int segment_level[4]; // filtering strength for each segments [0..63]
  186. int alpha_data_size; // size of the transparency data
  187. int layer_data_size; // size of the enhancement layer data
  188. // lossless encoder statistics
  189. uint32_t lossless_features; // bit0:predictor bit1:cross-color transform
  190. // bit2:subtract-green bit3:color indexing
  191. int histogram_bits; // number of precision bits of histogram
  192. int transform_bits; // precision bits for transform
  193. int cache_bits; // number of bits for color cache lookup
  194. int palette_size; // number of color in palette, if used
  195. int lossless_size; // final lossless size
  196. int lossless_hdr_size; // lossless header (transform, huffman etc) size
  197. int lossless_data_size; // lossless image data size
  198. uint32_t pad[2]; // padding for later use
  199. };
  200. // Signature for output function. Should return true if writing was successful.
  201. // data/data_size is the segment of data to write, and 'picture' is for
  202. // reference (and so one can make use of picture->custom_ptr).
  203. typedef int (*WebPWriterFunction)(const uint8_t* data, size_t data_size,
  204. const WebPPicture* picture);
  205. // WebPMemoryWrite: a special WebPWriterFunction that writes to memory using
  206. // the following WebPMemoryWriter object (to be set as a custom_ptr).
  207. struct WebPMemoryWriter {
  208. uint8_t* mem; // final buffer (of size 'max_size', larger than 'size').
  209. size_t size; // final size
  210. size_t max_size; // total capacity
  211. uint32_t pad[1]; // padding for later use
  212. };
  213. // The following must be called first before any use.
  214. WEBP_EXTERN(void) WebPMemoryWriterInit(WebPMemoryWriter* writer);
  215. // The following must be called to deallocate writer->mem memory. The 'writer'
  216. // object itself is not deallocated.
  217. WEBP_EXTERN(void) WebPMemoryWriterClear(WebPMemoryWriter* writer);
  218. // The custom writer to be used with WebPMemoryWriter as custom_ptr. Upon
  219. // completion, writer.mem and writer.size will hold the coded data.
  220. // writer.mem must be freed by calling WebPMemoryWriterClear.
  221. WEBP_EXTERN(int) WebPMemoryWrite(const uint8_t* data, size_t data_size,
  222. const WebPPicture* picture);
  223. // Progress hook, called from time to time to report progress. It can return
  224. // false to request an abort of the encoding process, or true otherwise if
  225. // everything is OK.
  226. typedef int (*WebPProgressHook)(int percent, const WebPPicture* picture);
  227. // Color spaces.
  228. typedef enum WebPEncCSP {
  229. // chroma sampling
  230. WEBP_YUV420 = 0, // 4:2:0
  231. WEBP_YUV420A = 4, // alpha channel variant
  232. WEBP_CSP_UV_MASK = 3, // bit-mask to get the UV sampling factors
  233. WEBP_CSP_ALPHA_BIT = 4 // bit that is set if alpha is present
  234. } WebPEncCSP;
  235. // Encoding error conditions.
  236. typedef enum WebPEncodingError {
  237. VP8_ENC_OK = 0,
  238. VP8_ENC_ERROR_OUT_OF_MEMORY, // memory error allocating objects
  239. VP8_ENC_ERROR_BITSTREAM_OUT_OF_MEMORY, // memory error while flushing bits
  240. VP8_ENC_ERROR_NULL_PARAMETER, // a pointer parameter is NULL
  241. VP8_ENC_ERROR_INVALID_CONFIGURATION, // configuration is invalid
  242. VP8_ENC_ERROR_BAD_DIMENSION, // picture has invalid width/height
  243. VP8_ENC_ERROR_PARTITION0_OVERFLOW, // partition is bigger than 512k
  244. VP8_ENC_ERROR_PARTITION_OVERFLOW, // partition is bigger than 16M
  245. VP8_ENC_ERROR_BAD_WRITE, // error while flushing bytes
  246. VP8_ENC_ERROR_FILE_TOO_BIG, // file is bigger than 4G
  247. VP8_ENC_ERROR_USER_ABORT, // abort request by user
  248. VP8_ENC_ERROR_LAST // list terminator. always last.
  249. } WebPEncodingError;
  250. // maximum width/height allowed (inclusive), in pixels
  251. #define WEBP_MAX_DIMENSION 16383
  252. // Main exchange structure (input samples, output bytes, statistics)
  253. struct WebPPicture {
  254. // INPUT
  255. //////////////
  256. // Main flag for encoder selecting between ARGB or YUV input.
  257. // It is recommended to use ARGB input (*argb, argb_stride) for lossless
  258. // compression, and YUV input (*y, *u, *v, etc.) for lossy compression
  259. // since these are the respective native colorspace for these formats.
  260. int use_argb;
  261. // YUV input (mostly used for input to lossy compression)
  262. WebPEncCSP colorspace; // colorspace: should be YUV420 for now (=Y'CbCr).
  263. int width, height; // dimensions (less or equal to WEBP_MAX_DIMENSION)
  264. uint8_t *y, *u, *v; // pointers to luma/chroma planes.
  265. int y_stride, uv_stride; // luma/chroma strides.
  266. uint8_t* a; // pointer to the alpha plane
  267. int a_stride; // stride of the alpha plane
  268. uint32_t pad1[2]; // padding for later use
  269. // ARGB input (mostly used for input to lossless compression)
  270. uint32_t* argb; // Pointer to argb (32 bit) plane.
  271. int argb_stride; // This is stride in pixels units, not bytes.
  272. uint32_t pad2[3]; // padding for later use
  273. // OUTPUT
  274. ///////////////
  275. // Byte-emission hook, to store compressed bytes as they are ready.
  276. WebPWriterFunction writer; // can be NULL
  277. void* custom_ptr; // can be used by the writer.
  278. // map for extra information (only for lossy compression mode)
  279. int extra_info_type; // 1: intra type, 2: segment, 3: quant
  280. // 4: intra-16 prediction mode,
  281. // 5: chroma prediction mode,
  282. // 6: bit cost, 7: distortion
  283. uint8_t* extra_info; // if not NULL, points to an array of size
  284. // ((width + 15) / 16) * ((height + 15) / 16) that
  285. // will be filled with a macroblock map, depending
  286. // on extra_info_type.
  287. // STATS AND REPORTS
  288. ///////////////////////////
  289. // Pointer to side statistics (updated only if not NULL)
  290. WebPAuxStats* stats;
  291. // Error code for the latest error encountered during encoding
  292. WebPEncodingError error_code;
  293. // If not NULL, report progress during encoding.
  294. WebPProgressHook progress_hook;
  295. void* user_data; // this field is free to be set to any value and
  296. // used during callbacks (like progress-report e.g.).
  297. uint32_t pad3[3]; // padding for later use
  298. // Unused for now
  299. uint8_t *pad4, *pad5;
  300. uint32_t pad6[8]; // padding for later use
  301. // PRIVATE FIELDS
  302. ////////////////////
  303. void* memory_; // row chunk of memory for yuva planes
  304. void* memory_argb_; // and for argb too.
  305. void* pad7[2]; // padding for later use
  306. };
  307. // Internal, version-checked, entry point
  308. WEBP_EXTERN(int) WebPPictureInitInternal(WebPPicture*, int);
  309. // Should always be called, to initialize the structure. Returns false in case
  310. // of version mismatch. WebPPictureInit() must have succeeded before using the
  311. // 'picture' object.
  312. // Note that, by default, use_argb is false and colorspace is WEBP_YUV420.
  313. static WEBP_INLINE int WebPPictureInit(WebPPicture* picture) {
  314. return WebPPictureInitInternal(picture, WEBP_ENCODER_ABI_VERSION);
  315. }
  316. //------------------------------------------------------------------------------
  317. // WebPPicture utils
  318. // Convenience allocation / deallocation based on picture->width/height:
  319. // Allocate y/u/v buffers as per colorspace/width/height specification.
  320. // Note! This function will free the previous buffer if needed.
  321. // Returns false in case of memory error.
  322. WEBP_EXTERN(int) WebPPictureAlloc(WebPPicture* picture);
  323. // Release the memory allocated by WebPPictureAlloc() or WebPPictureImport*().
  324. // Note that this function does _not_ free the memory used by the 'picture'
  325. // object itself.
  326. // Besides memory (which is reclaimed) all other fields of 'picture' are
  327. // preserved.
  328. WEBP_EXTERN(void) WebPPictureFree(WebPPicture* picture);
  329. // Copy the pixels of *src into *dst, using WebPPictureAlloc. Upon return, *dst
  330. // will fully own the copied pixels (this is not a view). The 'dst' picture need
  331. // not be initialized as its content is overwritten.
  332. // Returns false in case of memory allocation error.
  333. WEBP_EXTERN(int) WebPPictureCopy(const WebPPicture* src, WebPPicture* dst);
  334. // Compute PSNR, SSIM or LSIM distortion metric between two pictures. Results
  335. // are in dB, stored in result[] in the Y/U/V/Alpha/All or B/G/R/A/All order.
  336. // Returns false in case of error (src and ref don't have same dimension, ...)
  337. // Warning: this function is rather CPU-intensive.
  338. WEBP_EXTERN(int) WebPPictureDistortion(
  339. const WebPPicture* src, const WebPPicture* ref,
  340. int metric_type, // 0 = PSNR, 1 = SSIM, 2 = LSIM
  341. float result[5]);
  342. // self-crops a picture to the rectangle defined by top/left/width/height.
  343. // Returns false in case of memory allocation error, or if the rectangle is
  344. // outside of the source picture.
  345. // The rectangle for the view is defined by the top-left corner pixel
  346. // coordinates (left, top) as well as its width and height. This rectangle
  347. // must be fully be comprised inside the 'src' source picture. If the source
  348. // picture uses the YUV420 colorspace, the top and left coordinates will be
  349. // snapped to even values.
  350. WEBP_EXTERN(int) WebPPictureCrop(WebPPicture* picture,
  351. int left, int top, int width, int height);
  352. // Extracts a view from 'src' picture into 'dst'. The rectangle for the view
  353. // is defined by the top-left corner pixel coordinates (left, top) as well
  354. // as its width and height. This rectangle must be fully be comprised inside
  355. // the 'src' source picture. If the source picture uses the YUV420 colorspace,
  356. // the top and left coordinates will be snapped to even values.
  357. // Picture 'src' must out-live 'dst' picture. Self-extraction of view is allowed
  358. // ('src' equal to 'dst') as a mean of fast-cropping (but note that doing so,
  359. // the original dimension will be lost). Picture 'dst' need not be initialized
  360. // with WebPPictureInit() if it is different from 'src', since its content will
  361. // be overwritten.
  362. // Returns false in case of memory allocation error or invalid parameters.
  363. WEBP_EXTERN(int) WebPPictureView(const WebPPicture* src,
  364. int left, int top, int width, int height,
  365. WebPPicture* dst);
  366. // Returns true if the 'picture' is actually a view and therefore does
  367. // not own the memory for pixels.
  368. WEBP_EXTERN(int) WebPPictureIsView(const WebPPicture* picture);
  369. // Rescale a picture to new dimension width x height.
  370. // If either 'width' or 'height' (but not both) is 0 the corresponding
  371. // dimension will be calculated preserving the aspect ratio.
  372. // No gamma correction is applied.
  373. // Returns false in case of error (invalid parameter or insufficient memory).
  374. WEBP_EXTERN(int) WebPPictureRescale(WebPPicture* pic, int width, int height);
  375. // Colorspace conversion function to import RGB samples.
  376. // Previous buffer will be free'd, if any.
  377. // *rgb buffer should have a size of at least height * rgb_stride.
  378. // Returns false in case of memory error.
  379. WEBP_EXTERN(int) WebPPictureImportRGB(
  380. WebPPicture* picture, const uint8_t* rgb, int rgb_stride);
  381. // Same, but for RGBA buffer.
  382. WEBP_EXTERN(int) WebPPictureImportRGBA(
  383. WebPPicture* picture, const uint8_t* rgba, int rgba_stride);
  384. // Same, but for RGBA buffer. Imports the RGB direct from the 32-bit format
  385. // input buffer ignoring the alpha channel. Avoids needing to copy the data
  386. // to a temporary 24-bit RGB buffer to import the RGB only.
  387. WEBP_EXTERN(int) WebPPictureImportRGBX(
  388. WebPPicture* picture, const uint8_t* rgbx, int rgbx_stride);
  389. // Variants of the above, but taking BGR(A|X) input.
  390. WEBP_EXTERN(int) WebPPictureImportBGR(
  391. WebPPicture* picture, const uint8_t* bgr, int bgr_stride);
  392. WEBP_EXTERN(int) WebPPictureImportBGRA(
  393. WebPPicture* picture, const uint8_t* bgra, int bgra_stride);
  394. WEBP_EXTERN(int) WebPPictureImportBGRX(
  395. WebPPicture* picture, const uint8_t* bgrx, int bgrx_stride);
  396. // Converts picture->argb data to the YUV420A format. The 'colorspace'
  397. // parameter is deprecated and should be equal to WEBP_YUV420.
  398. // Upon return, picture->use_argb is set to false. The presence of real
  399. // non-opaque transparent values is detected, and 'colorspace' will be
  400. // adjusted accordingly. Note that this method is lossy.
  401. // Returns false in case of error.
  402. WEBP_EXTERN(int) WebPPictureARGBToYUVA(WebPPicture* picture,
  403. WebPEncCSP /*colorspace = WEBP_YUV420*/);
  404. // Same as WebPPictureARGBToYUVA(), but the conversion is done using
  405. // pseudo-random dithering with a strength 'dithering' between
  406. // 0.0 (no dithering) and 1.0 (maximum dithering). This is useful
  407. // for photographic picture.
  408. WEBP_EXTERN(int) WebPPictureARGBToYUVADithered(
  409. WebPPicture* picture, WebPEncCSP colorspace, float dithering);
  410. // Performs 'smart' RGBA->YUVA420 downsampling and colorspace conversion.
  411. // Downsampling is handled with extra care in case of color clipping. This
  412. // method is roughly 2x slower than WebPPictureARGBToYUVA() but produces better
  413. // YUV representation.
  414. // Returns false in case of error.
  415. WEBP_EXTERN(int) WebPPictureSmartARGBToYUVA(WebPPicture* picture);
  416. // Converts picture->yuv to picture->argb and sets picture->use_argb to true.
  417. // The input format must be YUV_420 or YUV_420A.
  418. // Note that the use of this method is discouraged if one has access to the
  419. // raw ARGB samples, since using YUV420 is comparatively lossy. Also, the
  420. // conversion from YUV420 to ARGB incurs a small loss too.
  421. // Returns false in case of error.
  422. WEBP_EXTERN(int) WebPPictureYUVAToARGB(WebPPicture* picture);
  423. // Helper function: given a width x height plane of RGBA or YUV(A) samples
  424. // clean-up the YUV or RGB samples under fully transparent area, to help
  425. // compressibility (no guarantee, though).
  426. WEBP_EXTERN(void) WebPCleanupTransparentArea(WebPPicture* picture);
  427. // Scan the picture 'picture' for the presence of non fully opaque alpha values.
  428. // Returns true in such case. Otherwise returns false (indicating that the
  429. // alpha plane can be ignored altogether e.g.).
  430. WEBP_EXTERN(int) WebPPictureHasTransparency(const WebPPicture* picture);
  431. // Remove the transparency information (if present) by blending the color with
  432. // the background color 'background_rgb' (specified as 24bit RGB triplet).
  433. // After this call, all alpha values are reset to 0xff.
  434. WEBP_EXTERN(void) WebPBlendAlpha(WebPPicture* pic, uint32_t background_rgb);
  435. //------------------------------------------------------------------------------
  436. // Main call
  437. // Main encoding call, after config and picture have been initialized.
  438. // 'picture' must be less than 16384x16384 in dimension (cf WEBP_MAX_DIMENSION),
  439. // and the 'config' object must be a valid one.
  440. // Returns false in case of error, true otherwise.
  441. // In case of error, picture->error_code is updated accordingly.
  442. // 'picture' can hold the source samples in both YUV(A) or ARGB input, depending
  443. // on the value of 'picture->use_argb'. It is highly recommended to use
  444. // the former for lossy encoding, and the latter for lossless encoding
  445. // (when config.lossless is true). Automatic conversion from one format to
  446. // another is provided but they both incur some loss.
  447. WEBP_EXTERN(int) WebPEncode(const WebPConfig* config, WebPPicture* picture);
  448. //------------------------------------------------------------------------------
  449. #ifdef __cplusplus
  450. } // extern "C"
  451. #endif
  452. #endif /* WEBP_WEBP_ENCODE_H_ */