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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
14 #ifndef WEBP_WEBP_ENCODE_H_
15 #define WEBP_WEBP_ENCODE_H_
16
17 #include "./types.h"
18
19 #ifdef __cplusplus
20 extern "C" {
21 #endif
22
23 #define WEBP_ENCODER_ABI_VERSION 0x0210 // 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 WebPImageHint WebPImageHint;
28 // typedef enum WebPEncCSP WebPEncCSP;
29 // typedef enum WebPPreset WebPPreset;
30 // typedef enum WebPEncodingError WebPEncodingError;
31 typedef struct WebPConfig WebPConfig;
32 typedef struct WebPPicture WebPPicture; // main structure for I/O
33 typedef struct WebPAuxStats WebPAuxStats;
34 typedef struct WebPMemoryWriter WebPMemoryWriter;
35
36 // Return the encoder's version number, packed in hexadecimal using 8bits for
37 // each of major/minor/revision. E.g: v2.5.7 is 0x020507.
38 WEBP_EXTERN int WebPGetEncoderVersion(void);
39
40 //------------------------------------------------------------------------------
41 // One-stop-shop call! No questions asked:
42
43 // Returns the size of the compressed data (pointed to by *output), or 0 if
44 // an error occurred. The compressed data must be released by the caller
45 // using the call 'WebPFree(*output)'.
46 // These functions compress using the lossy format, and the quality_factor
47 // can go from 0 (smaller output, lower quality) to 100 (best quality,
48 // larger output).
49 WEBP_EXTERN size_t WebPEncodeRGB(const uint8_t* rgb,
50 int width, int height, int stride,
51 float quality_factor, uint8_t** output);
52 WEBP_EXTERN size_t WebPEncodeBGR(const uint8_t* bgr,
53 int width, int height, int stride,
54 float quality_factor, uint8_t** output);
55 WEBP_EXTERN size_t WebPEncodeRGBA(const uint8_t* rgba,
56 int width, int height, int stride,
57 float quality_factor, uint8_t** output);
58 WEBP_EXTERN size_t WebPEncodeBGRA(const uint8_t* bgra,
59 int width, int height, int stride,
60 float quality_factor, uint8_t** output);
61
62 // These functions are the equivalent of the above, but compressing in a
63 // lossless manner. Files are usually larger than lossy format, but will
64 // not suffer any compression loss.
65 // Note these functions, like the lossy versions, use the library's default
66 // settings. For lossless this means 'exact' is disabled. RGB values in
67 // transparent areas will be modified to improve compression. To avoid this,
68 // use WebPEncode() and set WebPConfig::exact to 1.
69 WEBP_EXTERN size_t WebPEncodeLosslessRGB(const uint8_t* rgb,
70 int width, int height, int stride,
71 uint8_t** output);
72 WEBP_EXTERN size_t WebPEncodeLosslessBGR(const uint8_t* bgr,
73 int width, int height, int stride,
74 uint8_t** output);
75 WEBP_EXTERN size_t WebPEncodeLosslessRGBA(const uint8_t* rgba,
76 int width, int height, int stride,
77 uint8_t** output);
78 WEBP_EXTERN size_t WebPEncodeLosslessBGRA(const uint8_t* bgra,
79 int width, int height, int stride,
80 uint8_t** output);
81
82 //------------------------------------------------------------------------------
83 // Coding parameters
84
85 // Image characteristics hint for the underlying encoder.
86 typedef enum WebPImageHint {
87 WEBP_HINT_DEFAULT = 0, // default preset.
88 WEBP_HINT_PICTURE, // digital picture, like portrait, inner shot
89 WEBP_HINT_PHOTO, // outdoor photograph, with natural lighting
90 WEBP_HINT_GRAPH, // Discrete tone image (graph, map-tile etc).
91 WEBP_HINT_LAST
92 } WebPImageHint;
93
94 // Compression parameters.
95 struct WebPConfig {
96 int lossless; // Lossless encoding (0=lossy(default), 1=lossless).
97 float quality; // between 0 and 100. For lossy, 0 gives the smallest
98 // size and 100 the largest. For lossless, this
99 // parameter is the amount of effort put into the
100 // compression: 0 is the fastest but gives larger
101 // files compared to the slowest, but best, 100.
102 int method; // quality/speed trade-off (0=fast, 6=slower-better)
103
104 WebPImageHint image_hint; // Hint for image type (lossless only for now).
105
106 int target_size; // if non-zero, set the desired target size in bytes.
107 // Takes precedence over the 'compression' parameter.
108 float target_PSNR; // if non-zero, specifies the minimal distortion to
109 // try to achieve. Takes precedence over target_size.
110 int segments; // maximum number of segments to use, in [1..4]
111 int sns_strength; // Spatial Noise Shaping. 0=off, 100=maximum.
112 int filter_strength; // range: [0 = off .. 100 = strongest]
113 int filter_sharpness; // range: [0 = off .. 7 = least sharp]
114 int filter_type; // filtering type: 0 = simple, 1 = strong (only used
115 // if filter_strength > 0 or autofilter > 0)
116 int autofilter; // Auto adjust filter's strength [0 = off, 1 = on]
117 int alpha_compression; // Algorithm for encoding the alpha plane (0 = none,
118 // 1 = compressed with WebP lossless). Default is 1.
119 int alpha_filtering; // Predictive filtering method for alpha plane.
120 // 0: none, 1: fast, 2: best. Default if 1.
121 int alpha_quality; // Between 0 (smallest size) and 100 (lossless).
122 // Default is 100.
123 int pass; // number of entropy-analysis passes (in [1..10]).
124
125 int show_compressed; // if true, export the compressed picture back.
126 // In-loop filtering is not applied.
127 int preprocessing; // preprocessing filter:
128 // 0=none, 1=segment-smooth, 2=pseudo-random dithering
129 int partitions; // log2(number of token partitions) in [0..3]. Default
130 // is set to 0 for easier progressive decoding.
131 int partition_limit; // quality degradation allowed to fit the 512k limit
132 // on prediction modes coding (0: no degradation,
133 // 100: maximum possible degradation).
134 int emulate_jpeg_size; // If true, compression parameters will be remapped
135 // to better match the expected output size from
136 // JPEG compression. Generally, the output size will
137 // be similar but the degradation will be lower.
138 int thread_level; // If non-zero, try and use multi-threaded encoding.
139 int low_memory; // If set, reduce memory usage (but increase CPU use).
140
141 int near_lossless; // Near lossless encoding [0 = max loss .. 100 = off
142 // (default)].
143 int exact; // if non-zero, preserve the exact RGB values under
144 // transparent area. Otherwise, discard this invisible
145 // RGB information for better compression. The default
146 // value is 0.
147
148 int use_delta_palette; // reserved
149 int use_sharp_yuv; // if needed, use sharp (and slow) RGB->YUV conversion
150
151 int qmin; // minimum permissible quality factor
152 int qmax; // maximum permissible quality factor
153 };
154
155 // Enumerate some predefined settings for WebPConfig, depending on the type
156 // of source picture. These presets are used when calling WebPConfigPreset().
157 typedef enum WebPPreset {
158 WEBP_PRESET_DEFAULT = 0, // default preset.
159 WEBP_PRESET_PICTURE, // digital picture, like portrait, inner shot
160 WEBP_PRESET_PHOTO, // outdoor photograph, with natural lighting
161 WEBP_PRESET_DRAWING, // hand or line drawing, with high-contrast details
162 WEBP_PRESET_ICON, // small-sized colorful images
163 WEBP_PRESET_TEXT // text-like
164 } WebPPreset;
165
166 // Internal, version-checked, entry point
167 WEBP_NODISCARD WEBP_EXTERN int WebPConfigInitInternal(WebPConfig*, WebPPreset,
168 float, int);
169
170 // Should always be called, to initialize a fresh WebPConfig structure before
171 // modification. Returns false in case of version mismatch. WebPConfigInit()
172 // must have succeeded before using the 'config' object.
173 // Note that the default values are lossless=0 and quality=75.
174 WEBP_NODISCARD static WEBP_INLINE int WebPConfigInit(WebPConfig* config) {
175 return WebPConfigInitInternal(config, WEBP_PRESET_DEFAULT, 75.f,
176 WEBP_ENCODER_ABI_VERSION);
177 }
178
179 // This function will initialize the configuration according to a predefined
180 // set of parameters (referred to by 'preset') and a given quality factor.
181 // This function can be called as a replacement to WebPConfigInit(). Will
182 // return false in case of error.
183 WEBP_NODISCARD static WEBP_INLINE int WebPConfigPreset(WebPConfig* config,
184 WebPPreset preset,
185 float quality) {
186 return WebPConfigInitInternal(config, preset, quality,
187 WEBP_ENCODER_ABI_VERSION);
188 }
189
190 // Activate the lossless compression mode with the desired efficiency level
191 // between 0 (fastest, lowest compression) and 9 (slower, best compression).
192 // A good default level is '6', providing a fair tradeoff between compression
193 // speed and final compressed size.
194 // This function will overwrite several fields from config: 'method', 'quality'
195 // and 'lossless'. Returns false in case of parameter error.
196 WEBP_NODISCARD WEBP_EXTERN int WebPConfigLosslessPreset(WebPConfig* config,
197 int level);
198
199 // Returns true if 'config' is non-NULL and all configuration parameters are
200 // within their valid ranges.
201 WEBP_NODISCARD WEBP_EXTERN int WebPValidateConfig(const WebPConfig* config);
202
203 //------------------------------------------------------------------------------
204 // Input / Output
205 // Structure for storing auxiliary statistics.
206
207 struct WebPAuxStats {
208 int coded_size; // final size
209
210 float PSNR[5]; // peak-signal-to-noise ratio for Y/U/V/All/Alpha
211 int block_count[3]; // number of intra4/intra16/skipped macroblocks
212 int header_bytes[2]; // approximate number of bytes spent for header
213 // and mode-partition #0
214 int residual_bytes[3][4]; // approximate number of bytes spent for
215 // DC/AC/uv coefficients for each (0..3) segments.
216 int segment_size[4]; // number of macroblocks in each segments
217 int segment_quant[4]; // quantizer values for each segments
218 int segment_level[4]; // filtering strength for each segments [0..63]
219
220 int alpha_data_size; // size of the transparency data
221 int layer_data_size; // size of the enhancement layer data
222
223 // lossless encoder statistics
224 uint32_t lossless_features; // bit0:predictor bit1:cross-color transform
225 // bit2:subtract-green bit3:color indexing
226 int histogram_bits; // number of precision bits of histogram
227 int transform_bits; // precision bits for predictor transform
228 int cache_bits; // number of bits for color cache lookup
229 int palette_size; // number of color in palette, if used
230 int lossless_size; // final lossless size
231 int lossless_hdr_size; // lossless header (transform, huffman etc) size
232 int lossless_data_size; // lossless image data size
233 int cross_color_transform_bits; // precision bits for cross-color transform
234
235 uint32_t pad[1]; // padding for later use
236 };
237
238 // Signature for output function. Should return true if writing was successful.
239 // data/data_size is the segment of data to write, and 'picture' is for
240 // reference (and so one can make use of picture->custom_ptr).
241 typedef int (*WebPWriterFunction)(const uint8_t* data, size_t data_size,
242 const WebPPicture* picture);
243
244 // WebPMemoryWrite: a special WebPWriterFunction that writes to memory using
245 // the following WebPMemoryWriter object (to be set as a custom_ptr).
246 struct WebPMemoryWriter {
247 uint8_t* mem; // final buffer (of size 'max_size', larger than 'size').
248 size_t size; // final size
249 size_t max_size; // total capacity
250 uint32_t pad[1]; // padding for later use
251 };
252
253 // The following must be called first before any use.
254 WEBP_EXTERN void WebPMemoryWriterInit(WebPMemoryWriter* writer);
255
256 // The following must be called to deallocate writer->mem memory. The 'writer'
257 // object itself is not deallocated.
258 WEBP_EXTERN void WebPMemoryWriterClear(WebPMemoryWriter* writer);
259 // The custom writer to be used with WebPMemoryWriter as custom_ptr. Upon
260 // completion, writer.mem and writer.size will hold the coded data.
261 // writer.mem must be freed by calling WebPMemoryWriterClear.
262 WEBP_NODISCARD WEBP_EXTERN int WebPMemoryWrite(
263 const uint8_t* data, size_t data_size, const WebPPicture* picture);
264
265 // Progress hook, called from time to time to report progress. It can return
266 // false to request an abort of the encoding process, or true otherwise if
267 // everything is OK.
268 typedef int (*WebPProgressHook)(int percent, const WebPPicture* picture);
269
270 // Color spaces.
271 typedef enum WebPEncCSP {
272 // chroma sampling
273 WEBP_YUV420 = 0, // 4:2:0
274 WEBP_YUV420A = 4, // alpha channel variant
275 WEBP_CSP_UV_MASK = 3, // bit-mask to get the UV sampling factors
276 WEBP_CSP_ALPHA_BIT = 4 // bit that is set if alpha is present
277 } WebPEncCSP;
278
279 // Encoding error conditions.
280 typedef enum WebPEncodingError {
281 VP8_ENC_OK = 0,
282 VP8_ENC_ERROR_OUT_OF_MEMORY, // memory error allocating objects
283 VP8_ENC_ERROR_BITSTREAM_OUT_OF_MEMORY, // memory error while flushing bits
284 VP8_ENC_ERROR_NULL_PARAMETER, // a pointer parameter is NULL
285 VP8_ENC_ERROR_INVALID_CONFIGURATION, // configuration is invalid
286 VP8_ENC_ERROR_BAD_DIMENSION, // picture has invalid width/height
287 VP8_ENC_ERROR_PARTITION0_OVERFLOW, // partition is bigger than 512k
288 VP8_ENC_ERROR_PARTITION_OVERFLOW, // partition is bigger than 16M
289 VP8_ENC_ERROR_BAD_WRITE, // error while flushing bytes
290 VP8_ENC_ERROR_FILE_TOO_BIG, // file is bigger than 4G
291 VP8_ENC_ERROR_USER_ABORT, // abort request by user
292 VP8_ENC_ERROR_LAST // list terminator. always last.
293 } WebPEncodingError;
294
295 // maximum width/height allowed (inclusive), in pixels
296 #define WEBP_MAX_DIMENSION 16383
297
298 // Main exchange structure (input samples, output bytes, statistics)
299 //
300 // Once WebPPictureInit() has been called, it's ok to make all the INPUT fields
301 // (use_argb, y/u/v, argb, ...) point to user-owned data, even if
302 // WebPPictureAlloc() has been called. Depending on the value use_argb,
303 // it's guaranteed that either *argb or *y/*u/*v content will be kept untouched.
304 struct WebPPicture {
305 // INPUT
306 //////////////
307 // Main flag for encoder selecting between ARGB or YUV input.
308 // It is recommended to use ARGB input (*argb, argb_stride) for lossless
309 // compression, and YUV input (*y, *u, *v, etc.) for lossy compression
310 // since these are the respective native colorspace for these formats.
311 int use_argb;
312
313 // YUV input (mostly used for input to lossy compression)
314 WebPEncCSP colorspace; // colorspace: should be YUV420 for now (=Y'CbCr).
315 int width, height; // dimensions (less or equal to WEBP_MAX_DIMENSION)
316 uint8_t* y, *u, *v; // pointers to luma/chroma planes.
317 int y_stride, uv_stride; // luma/chroma strides.
318 uint8_t* a; // pointer to the alpha plane
319 int a_stride; // stride of the alpha plane
320 uint32_t pad1[2]; // padding for later use
321
322 // ARGB input (mostly used for input to lossless compression)
323 uint32_t* argb; // Pointer to argb (32 bit) plane.
324 int argb_stride; // This is stride in pixels units, not bytes.
325 uint32_t pad2[3]; // padding for later use
326
327 // OUTPUT
328 ///////////////
329 // Byte-emission hook, to store compressed bytes as they are ready.
330 WebPWriterFunction writer; // can be NULL
331 void* custom_ptr; // can be used by the writer.
332
333 // map for extra information (only for lossy compression mode)
334 int extra_info_type; // 1: intra type, 2: segment, 3: quant
335 // 4: intra-16 prediction mode,
336 // 5: chroma prediction mode,
337 // 6: bit cost, 7: distortion
338 uint8_t* extra_info; // if not NULL, points to an array of size
339 // ((width + 15) / 16) * ((height + 15) / 16) that
340 // will be filled with a macroblock map, depending
341 // on extra_info_type.
342
343 // STATS AND REPORTS
344 ///////////////////////////
345 // Pointer to side statistics (updated only if not NULL)
346 WebPAuxStats* stats;
347
348 // Error code for the latest error encountered during encoding
349 WebPEncodingError error_code;
350
351 // If not NULL, report progress during encoding.
352 WebPProgressHook progress_hook;
353
354 void* user_data; // this field is free to be set to any value and
355 // used during callbacks (like progress-report e.g.).
356
357 uint32_t pad3[3]; // padding for later use
358
359 // Unused for now
360 uint8_t* pad4, *pad5;
361 uint32_t pad6[8]; // padding for later use
362
363 // PRIVATE FIELDS
364 ////////////////////
365 void* memory_; // row chunk of memory for yuva planes
366 void* memory_argb_; // and for argb too.
367 void* pad7[2]; // padding for later use
368 };
369
370 // Internal, version-checked, entry point
371 WEBP_NODISCARD WEBP_EXTERN int WebPPictureInitInternal(WebPPicture*, int);
372
373 // Should always be called, to initialize the structure. Returns false in case
374 // of version mismatch. WebPPictureInit() must have succeeded before using the
375 // 'picture' object.
376 // Note that, by default, use_argb is false and colorspace is WEBP_YUV420.
377 WEBP_NODISCARD static WEBP_INLINE int WebPPictureInit(WebPPicture* picture) {
378 return WebPPictureInitInternal(picture, WEBP_ENCODER_ABI_VERSION);
379 }
380
381 //------------------------------------------------------------------------------
382 // WebPPicture utils
383
384 // Convenience allocation / deallocation based on picture->width/height:
385 // Allocate y/u/v buffers as per colorspace/width/height specification.
386 // Note! This function will free the previous buffer if needed.
387 // Returns false in case of memory error.
388 WEBP_NODISCARD WEBP_EXTERN int WebPPictureAlloc(WebPPicture* picture);
389
390 // Release the memory allocated by WebPPictureAlloc() or WebPPictureImport*().
391 // Note that this function does _not_ free the memory used by the 'picture'
392 // object itself.
393 // Besides memory (which is reclaimed) all other fields of 'picture' are
394 // preserved.
395 WEBP_EXTERN void WebPPictureFree(WebPPicture* picture);
396
397 // Copy the pixels of *src into *dst, using WebPPictureAlloc. Upon return, *dst
398 // will fully own the copied pixels (this is not a view). The 'dst' picture need
399 // not be initialized as its content is overwritten.
400 // Returns false in case of memory allocation error.
401 WEBP_NODISCARD WEBP_EXTERN int WebPPictureCopy(const WebPPicture* src,
402 WebPPicture* dst);
403
404 // Compute the single distortion for packed planes of samples.
405 // 'src' will be compared to 'ref', and the raw distortion stored into
406 // '*distortion'. The refined metric (log(MSE), log(1 - ssim),...' will be
407 // stored in '*result'.
408 // 'x_step' is the horizontal stride (in bytes) between samples.
409 // 'src/ref_stride' is the byte distance between rows.
410 // Returns false in case of error (bad parameter, memory allocation error, ...).
411 WEBP_NODISCARD WEBP_EXTERN int WebPPlaneDistortion(
412 const uint8_t* src, size_t src_stride,
413 const uint8_t* ref, size_t ref_stride, int width, int height, size_t x_step,
414 int type, // 0 = PSNR, 1 = SSIM, 2 = LSIM
415 float* distortion, float* result);
416
417 // Compute PSNR, SSIM or LSIM distortion metric between two pictures. Results
418 // are in dB, stored in result[] in the B/G/R/A/All order. The distortion is
419 // always performed using ARGB samples. Hence if the input is YUV(A), the
420 // picture will be internally converted to ARGB (just for the measurement).
421 // Warning: this function is rather CPU-intensive.
422 WEBP_NODISCARD WEBP_EXTERN int WebPPictureDistortion(
423 const WebPPicture* src, const WebPPicture* ref,
424 int metric_type, // 0 = PSNR, 1 = SSIM, 2 = LSIM
425 float result[5]);
426
427 // self-crops a picture to the rectangle defined by top/left/width/height.
428 // Returns false in case of memory allocation error, or if the rectangle is
429 // outside of the source picture.
430 // The rectangle for the view is defined by the top-left corner pixel
431 // coordinates (left, top) as well as its width and height. This rectangle
432 // must be fully be comprised inside the 'src' source picture. If the source
433 // picture uses the YUV420 colorspace, the top and left coordinates will be
434 // snapped to even values.
435 WEBP_NODISCARD WEBP_EXTERN int WebPPictureCrop(
436 WebPPicture* picture, int left, int top, int width, int height);
437
438 // Extracts a view from 'src' picture into 'dst'. The rectangle for the view
439 // is defined by the top-left corner pixel coordinates (left, top) as well
440 // as its width and height. This rectangle must be fully be comprised inside
441 // the 'src' source picture. If the source picture uses the YUV420 colorspace,
442 // the top and left coordinates will be snapped to even values.
443 // Picture 'src' must out-live 'dst' picture. Self-extraction of view is allowed
444 // ('src' equal to 'dst') as a mean of fast-cropping (but note that doing so,
445 // the original dimension will be lost). Picture 'dst' need not be initialized
446 // with WebPPictureInit() if it is different from 'src', since its content will
447 // be overwritten.
448 // Returns false in case of invalid parameters.
449 WEBP_NODISCARD WEBP_EXTERN int WebPPictureView(
450 const WebPPicture* src, int left, int top, int width, int height,
451 WebPPicture* dst);
452
453 // Returns true if the 'picture' is actually a view and therefore does
454 // not own the memory for pixels.
455 WEBP_EXTERN int WebPPictureIsView(const WebPPicture* picture);
456
457 // Rescale a picture to new dimension width x height.
458 // If either 'width' or 'height' (but not both) is 0 the corresponding
459 // dimension will be calculated preserving the aspect ratio.
460 // No gamma correction is applied.
461 // Returns false in case of error (invalid parameter or insufficient memory).
462 WEBP_NODISCARD WEBP_EXTERN int WebPPictureRescale(WebPPicture* picture,
463 int width, int height);
464
465 // Colorspace conversion function to import RGB samples.
466 // Previous buffer will be free'd, if any.
467 // *rgb buffer should have a size of at least height * rgb_stride.
468 // Returns false in case of memory error.
469 WEBP_NODISCARD WEBP_EXTERN int WebPPictureImportRGB(
470 WebPPicture* picture, const uint8_t* rgb, int rgb_stride);
471 // Same, but for RGBA buffer.
472 WEBP_NODISCARD WEBP_EXTERN int WebPPictureImportRGBA(
473 WebPPicture* picture, const uint8_t* rgba, int rgba_stride);
474 // Same, but for RGBA buffer. Imports the RGB direct from the 32-bit format
475 // input buffer ignoring the alpha channel. Avoids needing to copy the data
476 // to a temporary 24-bit RGB buffer to import the RGB only.
477 WEBP_NODISCARD WEBP_EXTERN int WebPPictureImportRGBX(
478 WebPPicture* picture, const uint8_t* rgbx, int rgbx_stride);
479
480 // Variants of the above, but taking BGR(A|X) input.
481 WEBP_NODISCARD WEBP_EXTERN int WebPPictureImportBGR(
482 WebPPicture* picture, const uint8_t* bgr, int bgr_stride);
483 WEBP_NODISCARD WEBP_EXTERN int WebPPictureImportBGRA(
484 WebPPicture* picture, const uint8_t* bgra, int bgra_stride);
485 WEBP_NODISCARD WEBP_EXTERN int WebPPictureImportBGRX(
486 WebPPicture* picture, const uint8_t* bgrx, int bgrx_stride);
487
488 // Converts picture->argb data to the YUV420A format. The 'colorspace'
489 // parameter is deprecated and should be equal to WEBP_YUV420.
490 // Upon return, picture->use_argb is set to false. The presence of real
491 // non-opaque transparent values is detected, and 'colorspace' will be
492 // adjusted accordingly. Note that this method is lossy.
493 // Returns false in case of error.
494 WEBP_NODISCARD WEBP_EXTERN int WebPPictureARGBToYUVA(
495 WebPPicture* picture, WebPEncCSP /*colorspace = WEBP_YUV420*/);
496
497 // Same as WebPPictureARGBToYUVA(), but the conversion is done using
498 // pseudo-random dithering with a strength 'dithering' between
499 // 0.0 (no dithering) and 1.0 (maximum dithering). This is useful
500 // for photographic picture.
501 WEBP_NODISCARD WEBP_EXTERN int WebPPictureARGBToYUVADithered(
502 WebPPicture* picture, WebPEncCSP colorspace, float dithering);
503
504 // Performs 'sharp' RGBA->YUVA420 downsampling and colorspace conversion
505 // Downsampling is handled with extra care in case of color clipping. This
506 // method is roughly 2x slower than WebPPictureARGBToYUVA() but produces better
507 // and sharper YUV representation.
508 // Returns false in case of error.
509 WEBP_NODISCARD WEBP_EXTERN int WebPPictureSharpARGBToYUVA(WebPPicture* picture);
510 // kept for backward compatibility:
511 WEBP_NODISCARD WEBP_EXTERN int WebPPictureSmartARGBToYUVA(WebPPicture* picture);
512
513 // Converts picture->yuv to picture->argb and sets picture->use_argb to true.
514 // The input format must be YUV_420 or YUV_420A. The conversion from YUV420 to
515 // ARGB incurs a small loss too.
516 // Note that the use of this colorspace is discouraged if one has access to the
517 // raw ARGB samples, since using YUV420 is comparatively lossy.
518 // Returns false in case of error.
519 WEBP_NODISCARD WEBP_EXTERN int WebPPictureYUVAToARGB(WebPPicture* picture);
520
521 // Helper function: given a width x height plane of RGBA or YUV(A) samples
522 // clean-up or smoothen the YUV or RGB samples under fully transparent area,
523 // to help compressibility (no guarantee, though).
524 WEBP_EXTERN void WebPCleanupTransparentArea(WebPPicture* picture);
525
526 // Scan the picture 'picture' for the presence of non fully opaque alpha values.
527 // Returns true in such case. Otherwise returns false (indicating that the
528 // alpha plane can be ignored altogether e.g.).
529 WEBP_EXTERN int WebPPictureHasTransparency(const WebPPicture* picture);
530
531 // Remove the transparency information (if present) by blending the color with
532 // the background color 'background_rgb' (specified as 24bit RGB triplet).
533 // After this call, all alpha values are reset to 0xff.
534 WEBP_EXTERN void WebPBlendAlpha(WebPPicture* picture, uint32_t background_rgb);
535
536 //------------------------------------------------------------------------------
537 // Main call
538
539 // Main encoding call, after config and picture have been initialized.
540 // 'picture' must be less than 16384x16384 in dimension (cf WEBP_MAX_DIMENSION),
541 // and the 'config' object must be a valid one.
542 // Returns false in case of error, true otherwise.
543 // In case of error, picture->error_code is updated accordingly.
544 // 'picture' can hold the source samples in both YUV(A) or ARGB input, depending
545 // on the value of 'picture->use_argb'. It is highly recommended to use
546 // the former for lossy encoding, and the latter for lossless encoding
547 // (when config.lossless is true). Automatic conversion from one format to
548 // another is provided but they both incur some loss.
549 WEBP_NODISCARD WEBP_EXTERN int WebPEncode(const WebPConfig* config,
550 WebPPicture* picture);
551
552 //------------------------------------------------------------------------------
553
554 #ifdef __cplusplus
555 } // extern "C"
556 #endif
557
558 #endif // WEBP_WEBP_ENCODE_H_