1 | // Copyright 2015 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 | // AnimDecoder implementation. |
11 | // |
12 | |
13 | #ifdef HAVE_CONFIG_H |
14 | #include "src/webp/config.h" |
15 | #endif |
16 | |
17 | #include <assert.h> |
18 | #include <string.h> |
19 | |
20 | #include "src/utils/utils.h" |
21 | #include "src/webp/decode.h" |
22 | #include "src/webp/demux.h" |
23 | |
24 | #define NUM_CHANNELS 4 |
25 | |
26 | typedef void (*BlendRowFunc)(uint32_t* const, const uint32_t* const, int); |
27 | static void BlendPixelRowNonPremult(uint32_t* const src, |
28 | const uint32_t* const dst, int num_pixels); |
29 | static void BlendPixelRowPremult(uint32_t* const src, const uint32_t* const dst, |
30 | int num_pixels); |
31 | |
32 | struct WebPAnimDecoder { |
33 | WebPDemuxer* demux_; // Demuxer created from given WebP bitstream. |
34 | WebPDecoderConfig config_; // Decoder config. |
35 | // Note: we use a pointer to a function blending multiple pixels at a time to |
36 | // allow possible inlining of per-pixel blending function. |
37 | BlendRowFunc blend_func_; // Pointer to the chose blend row function. |
38 | WebPAnimInfo info_; // Global info about the animation. |
39 | uint8_t* curr_frame_; // Current canvas (not disposed). |
40 | uint8_t* prev_frame_disposed_; // Previous canvas (properly disposed). |
41 | int prev_frame_timestamp_; // Previous frame timestamp (milliseconds). |
42 | WebPIterator prev_iter_; // Iterator object for previous frame. |
43 | int prev_frame_was_keyframe_; // True if previous frame was a keyframe. |
44 | int next_frame_; // Index of the next frame to be decoded |
45 | // (starting from 1). |
46 | }; |
47 | |
48 | static void DefaultDecoderOptions(WebPAnimDecoderOptions* const dec_options) { |
49 | dec_options->color_mode = MODE_RGBA; |
50 | dec_options->use_threads = 0; |
51 | } |
52 | |
53 | int WebPAnimDecoderOptionsInitInternal(WebPAnimDecoderOptions* dec_options, |
54 | int abi_version) { |
55 | if (dec_options == NULL || |
56 | WEBP_ABI_IS_INCOMPATIBLE(abi_version, WEBP_DEMUX_ABI_VERSION)) { |
57 | return 0; |
58 | } |
59 | DefaultDecoderOptions(dec_options); |
60 | return 1; |
61 | } |
62 | |
63 | static int ApplyDecoderOptions(const WebPAnimDecoderOptions* const dec_options, |
64 | WebPAnimDecoder* const dec) { |
65 | WEBP_CSP_MODE mode; |
66 | WebPDecoderConfig* config = &dec->config_; |
67 | assert(dec_options != NULL); |
68 | |
69 | mode = dec_options->color_mode; |
70 | if (mode != MODE_RGBA && mode != MODE_BGRA && |
71 | mode != MODE_rgbA && mode != MODE_bgrA) { |
72 | return 0; |
73 | } |
74 | dec->blend_func_ = (mode == MODE_RGBA || mode == MODE_BGRA) |
75 | ? &BlendPixelRowNonPremult |
76 | : &BlendPixelRowPremult; |
77 | WebPInitDecoderConfig(config); |
78 | config->output.colorspace = mode; |
79 | config->output.is_external_memory = 1; |
80 | config->options.use_threads = dec_options->use_threads; |
81 | // Note: config->output.u.RGBA is set at the time of decoding each frame. |
82 | return 1; |
83 | } |
84 | |
85 | WebPAnimDecoder* WebPAnimDecoderNewInternal( |
86 | const WebPData* webp_data, const WebPAnimDecoderOptions* dec_options, |
87 | int abi_version) { |
88 | WebPAnimDecoderOptions options; |
89 | WebPAnimDecoder* dec = NULL; |
90 | if (webp_data == NULL || |
91 | WEBP_ABI_IS_INCOMPATIBLE(abi_version, WEBP_DEMUX_ABI_VERSION)) { |
92 | return NULL; |
93 | } |
94 | |
95 | // Note: calloc() so that the pointer members are initialized to NULL. |
96 | dec = (WebPAnimDecoder*)WebPSafeCalloc(1ULL, sizeof(*dec)); |
97 | if (dec == NULL) goto Error; |
98 | |
99 | if (dec_options != NULL) { |
100 | options = *dec_options; |
101 | } else { |
102 | DefaultDecoderOptions(&options); |
103 | } |
104 | if (!ApplyDecoderOptions(&options, dec)) goto Error; |
105 | |
106 | dec->demux_ = WebPDemux(webp_data); |
107 | if (dec->demux_ == NULL) goto Error; |
108 | |
109 | dec->info_.canvas_width = WebPDemuxGetI(dec->demux_, WEBP_FF_CANVAS_WIDTH); |
110 | dec->info_.canvas_height = WebPDemuxGetI(dec->demux_, WEBP_FF_CANVAS_HEIGHT); |
111 | dec->info_.loop_count = WebPDemuxGetI(dec->demux_, WEBP_FF_LOOP_COUNT); |
112 | dec->info_.bgcolor = WebPDemuxGetI(dec->demux_, WEBP_FF_BACKGROUND_COLOR); |
113 | dec->info_.frame_count = WebPDemuxGetI(dec->demux_, WEBP_FF_FRAME_COUNT); |
114 | |
115 | // Note: calloc() because we fill frame with zeroes as well. |
116 | dec->curr_frame_ = (uint8_t*)WebPSafeCalloc( |
117 | dec->info_.canvas_width * NUM_CHANNELS, dec->info_.canvas_height); |
118 | if (dec->curr_frame_ == NULL) goto Error; |
119 | dec->prev_frame_disposed_ = (uint8_t*)WebPSafeCalloc( |
120 | dec->info_.canvas_width * NUM_CHANNELS, dec->info_.canvas_height); |
121 | if (dec->prev_frame_disposed_ == NULL) goto Error; |
122 | |
123 | WebPAnimDecoderReset(dec); |
124 | return dec; |
125 | |
126 | Error: |
127 | WebPAnimDecoderDelete(dec); |
128 | return NULL; |
129 | } |
130 | |
131 | int WebPAnimDecoderGetInfo(const WebPAnimDecoder* dec, WebPAnimInfo* info) { |
132 | if (dec == NULL || info == NULL) return 0; |
133 | *info = dec->info_; |
134 | return 1; |
135 | } |
136 | |
137 | // Returns true if the frame covers the full canvas. |
138 | static int IsFullFrame(int width, int height, int canvas_width, |
139 | int canvas_height) { |
140 | return (width == canvas_width && height == canvas_height); |
141 | } |
142 | |
143 | // Clear the canvas to transparent. |
144 | static int ZeroFillCanvas(uint8_t* buf, uint32_t canvas_width, |
145 | uint32_t canvas_height) { |
146 | const uint64_t size = |
147 | (uint64_t)canvas_width * canvas_height * NUM_CHANNELS * sizeof(*buf); |
148 | if (size != (size_t)size) return 0; |
149 | memset(buf, 0, (size_t)size); |
150 | return 1; |
151 | } |
152 | |
153 | // Clear given frame rectangle to transparent. |
154 | static void ZeroFillFrameRect(uint8_t* buf, int buf_stride, int x_offset, |
155 | int y_offset, int width, int height) { |
156 | int j; |
157 | assert(width * NUM_CHANNELS <= buf_stride); |
158 | buf += y_offset * buf_stride + x_offset * NUM_CHANNELS; |
159 | for (j = 0; j < height; ++j) { |
160 | memset(buf, 0, width * NUM_CHANNELS); |
161 | buf += buf_stride; |
162 | } |
163 | } |
164 | |
165 | // Copy width * height pixels from 'src' to 'dst'. |
166 | static int CopyCanvas(const uint8_t* src, uint8_t* dst, |
167 | uint32_t width, uint32_t height) { |
168 | const uint64_t size = (uint64_t)width * height * NUM_CHANNELS; |
169 | if (size != (size_t)size) return 0; |
170 | assert(src != NULL && dst != NULL); |
171 | memcpy(dst, src, (size_t)size); |
172 | return 1; |
173 | } |
174 | |
175 | // Returns true if the current frame is a key-frame. |
176 | static int IsKeyFrame(const WebPIterator* const curr, |
177 | const WebPIterator* const prev, |
178 | int prev_frame_was_key_frame, |
179 | int canvas_width, int canvas_height) { |
180 | if (curr->frame_num == 1) { |
181 | return 1; |
182 | } else if ((!curr->has_alpha || curr->blend_method == WEBP_MUX_NO_BLEND) && |
183 | IsFullFrame(curr->width, curr->height, |
184 | canvas_width, canvas_height)) { |
185 | return 1; |
186 | } else { |
187 | return (prev->dispose_method == WEBP_MUX_DISPOSE_BACKGROUND) && |
188 | (IsFullFrame(prev->width, prev->height, canvas_width, |
189 | canvas_height) || |
190 | prev_frame_was_key_frame); |
191 | } |
192 | } |
193 | |
194 | |
195 | // Blend a single channel of 'src' over 'dst', given their alpha channel values. |
196 | // 'src' and 'dst' are assumed to be NOT pre-multiplied by alpha. |
197 | static uint8_t BlendChannelNonPremult(uint32_t src, uint8_t src_a, |
198 | uint32_t dst, uint8_t dst_a, |
199 | uint32_t scale, int shift) { |
200 | const uint8_t src_channel = (src >> shift) & 0xff; |
201 | const uint8_t dst_channel = (dst >> shift) & 0xff; |
202 | const uint32_t blend_unscaled = src_channel * src_a + dst_channel * dst_a; |
203 | assert(blend_unscaled < (1ULL << 32) / scale); |
204 | return (blend_unscaled * scale) >> 24; |
205 | } |
206 | |
207 | // Blend 'src' over 'dst' assuming they are NOT pre-multiplied by alpha. |
208 | static uint32_t BlendPixelNonPremult(uint32_t src, uint32_t dst) { |
209 | const uint8_t src_a = (src >> 24) & 0xff; |
210 | |
211 | if (src_a == 0) { |
212 | return dst; |
213 | } else { |
214 | const uint8_t dst_a = (dst >> 24) & 0xff; |
215 | // This is the approximate integer arithmetic for the actual formula: |
216 | // dst_factor_a = (dst_a * (255 - src_a)) / 255. |
217 | const uint8_t dst_factor_a = (dst_a * (256 - src_a)) >> 8; |
218 | const uint8_t blend_a = src_a + dst_factor_a; |
219 | const uint32_t scale = (1UL << 24) / blend_a; |
220 | |
221 | const uint8_t blend_r = |
222 | BlendChannelNonPremult(src, src_a, dst, dst_factor_a, scale, 0); |
223 | const uint8_t blend_g = |
224 | BlendChannelNonPremult(src, src_a, dst, dst_factor_a, scale, 8); |
225 | const uint8_t blend_b = |
226 | BlendChannelNonPremult(src, src_a, dst, dst_factor_a, scale, 16); |
227 | assert(src_a + dst_factor_a < 256); |
228 | |
229 | return (blend_r << 0) | |
230 | (blend_g << 8) | |
231 | (blend_b << 16) | |
232 | ((uint32_t)blend_a << 24); |
233 | } |
234 | } |
235 | |
236 | // Blend 'num_pixels' in 'src' over 'dst' assuming they are NOT pre-multiplied |
237 | // by alpha. |
238 | static void BlendPixelRowNonPremult(uint32_t* const src, |
239 | const uint32_t* const dst, int num_pixels) { |
240 | int i; |
241 | for (i = 0; i < num_pixels; ++i) { |
242 | const uint8_t src_alpha = (src[i] >> 24) & 0xff; |
243 | if (src_alpha != 0xff) { |
244 | src[i] = BlendPixelNonPremult(src[i], dst[i]); |
245 | } |
246 | } |
247 | } |
248 | |
249 | // Individually multiply each channel in 'pix' by 'scale'. |
250 | static WEBP_INLINE uint32_t ChannelwiseMultiply(uint32_t pix, uint32_t scale) { |
251 | uint32_t mask = 0x00FF00FF; |
252 | uint32_t rb = ((pix & mask) * scale) >> 8; |
253 | uint32_t ag = ((pix >> 8) & mask) * scale; |
254 | return (rb & mask) | (ag & ~mask); |
255 | } |
256 | |
257 | // Blend 'src' over 'dst' assuming they are pre-multiplied by alpha. |
258 | static uint32_t BlendPixelPremult(uint32_t src, uint32_t dst) { |
259 | const uint8_t src_a = (src >> 24) & 0xff; |
260 | return src + ChannelwiseMultiply(dst, 256 - src_a); |
261 | } |
262 | |
263 | // Blend 'num_pixels' in 'src' over 'dst' assuming they are pre-multiplied by |
264 | // alpha. |
265 | static void BlendPixelRowPremult(uint32_t* const src, const uint32_t* const dst, |
266 | int num_pixels) { |
267 | int i; |
268 | for (i = 0; i < num_pixels; ++i) { |
269 | const uint8_t src_alpha = (src[i] >> 24) & 0xff; |
270 | if (src_alpha != 0xff) { |
271 | src[i] = BlendPixelPremult(src[i], dst[i]); |
272 | } |
273 | } |
274 | } |
275 | |
276 | // Returns two ranges (<left, width> pairs) at row 'canvas_y', that belong to |
277 | // 'src' but not 'dst'. A point range is empty if the corresponding width is 0. |
278 | static void FindBlendRangeAtRow(const WebPIterator* const src, |
279 | const WebPIterator* const dst, int canvas_y, |
280 | int* const left1, int* const width1, |
281 | int* const left2, int* const width2) { |
282 | const int src_max_x = src->x_offset + src->width; |
283 | const int dst_max_x = dst->x_offset + dst->width; |
284 | const int dst_max_y = dst->y_offset + dst->height; |
285 | assert(canvas_y >= src->y_offset && canvas_y < (src->y_offset + src->height)); |
286 | *left1 = -1; |
287 | *width1 = 0; |
288 | *left2 = -1; |
289 | *width2 = 0; |
290 | |
291 | if (canvas_y < dst->y_offset || canvas_y >= dst_max_y || |
292 | src->x_offset >= dst_max_x || src_max_x <= dst->x_offset) { |
293 | *left1 = src->x_offset; |
294 | *width1 = src->width; |
295 | return; |
296 | } |
297 | |
298 | if (src->x_offset < dst->x_offset) { |
299 | *left1 = src->x_offset; |
300 | *width1 = dst->x_offset - src->x_offset; |
301 | } |
302 | |
303 | if (src_max_x > dst_max_x) { |
304 | *left2 = dst_max_x; |
305 | *width2 = src_max_x - dst_max_x; |
306 | } |
307 | } |
308 | |
309 | int WebPAnimDecoderGetNext(WebPAnimDecoder* dec, |
310 | uint8_t** buf_ptr, int* timestamp_ptr) { |
311 | WebPIterator iter; |
312 | uint32_t width; |
313 | uint32_t height; |
314 | int is_key_frame; |
315 | int timestamp; |
316 | BlendRowFunc blend_row; |
317 | |
318 | if (dec == NULL || buf_ptr == NULL || timestamp_ptr == NULL) return 0; |
319 | if (!WebPAnimDecoderHasMoreFrames(dec)) return 0; |
320 | |
321 | width = dec->info_.canvas_width; |
322 | height = dec->info_.canvas_height; |
323 | blend_row = dec->blend_func_; |
324 | |
325 | // Get compressed frame. |
326 | if (!WebPDemuxGetFrame(dec->demux_, dec->next_frame_, &iter)) { |
327 | return 0; |
328 | } |
329 | timestamp = dec->prev_frame_timestamp_ + iter.duration; |
330 | |
331 | // Initialize. |
332 | is_key_frame = IsKeyFrame(&iter, &dec->prev_iter_, |
333 | dec->prev_frame_was_keyframe_, width, height); |
334 | if (is_key_frame) { |
335 | if (!ZeroFillCanvas(dec->curr_frame_, width, height)) { |
336 | goto Error; |
337 | } |
338 | } else { |
339 | if (!CopyCanvas(dec->prev_frame_disposed_, dec->curr_frame_, |
340 | width, height)) { |
341 | goto Error; |
342 | } |
343 | } |
344 | |
345 | // Decode. |
346 | { |
347 | const uint8_t* in = iter.fragment.bytes; |
348 | const size_t in_size = iter.fragment.size; |
349 | const size_t out_offset = |
350 | (iter.y_offset * width + iter.x_offset) * NUM_CHANNELS; |
351 | WebPDecoderConfig* const config = &dec->config_; |
352 | WebPRGBABuffer* const buf = &config->output.u.RGBA; |
353 | buf->stride = NUM_CHANNELS * width; |
354 | buf->size = buf->stride * iter.height; |
355 | buf->rgba = dec->curr_frame_ + out_offset; |
356 | |
357 | if (WebPDecode(in, in_size, config) != VP8_STATUS_OK) { |
358 | goto Error; |
359 | } |
360 | } |
361 | |
362 | // During the decoding of current frame, we may have set some pixels to be |
363 | // transparent (i.e. alpha < 255). However, the value of each of these |
364 | // pixels should have been determined by blending it against the value of |
365 | // that pixel in the previous frame if blending method of is WEBP_MUX_BLEND. |
366 | if (iter.frame_num > 1 && iter.blend_method == WEBP_MUX_BLEND && |
367 | !is_key_frame) { |
368 | if (dec->prev_iter_.dispose_method == WEBP_MUX_DISPOSE_NONE) { |
369 | int y; |
370 | // Blend transparent pixels with pixels in previous canvas. |
371 | for (y = 0; y < iter.height; ++y) { |
372 | const size_t offset = |
373 | (iter.y_offset + y) * width + iter.x_offset; |
374 | blend_row((uint32_t*)dec->curr_frame_ + offset, |
375 | (uint32_t*)dec->prev_frame_disposed_ + offset, iter.width); |
376 | } |
377 | } else { |
378 | int y; |
379 | assert(dec->prev_iter_.dispose_method == WEBP_MUX_DISPOSE_BACKGROUND); |
380 | // We need to blend a transparent pixel with its value just after |
381 | // initialization. That is, blend it with: |
382 | // * Fully transparent pixel if it belongs to prevRect <-- No-op. |
383 | // * The pixel in the previous canvas otherwise <-- Need alpha-blending. |
384 | for (y = 0; y < iter.height; ++y) { |
385 | const int canvas_y = iter.y_offset + y; |
386 | int left1, width1, left2, width2; |
387 | FindBlendRangeAtRow(&iter, &dec->prev_iter_, canvas_y, &left1, &width1, |
388 | &left2, &width2); |
389 | if (width1 > 0) { |
390 | const size_t offset1 = canvas_y * width + left1; |
391 | blend_row((uint32_t*)dec->curr_frame_ + offset1, |
392 | (uint32_t*)dec->prev_frame_disposed_ + offset1, width1); |
393 | } |
394 | if (width2 > 0) { |
395 | const size_t offset2 = canvas_y * width + left2; |
396 | blend_row((uint32_t*)dec->curr_frame_ + offset2, |
397 | (uint32_t*)dec->prev_frame_disposed_ + offset2, width2); |
398 | } |
399 | } |
400 | } |
401 | } |
402 | |
403 | // Update info of the previous frame and dispose it for the next iteration. |
404 | dec->prev_frame_timestamp_ = timestamp; |
405 | WebPDemuxReleaseIterator(&dec->prev_iter_); |
406 | dec->prev_iter_ = iter; |
407 | dec->prev_frame_was_keyframe_ = is_key_frame; |
408 | CopyCanvas(dec->curr_frame_, dec->prev_frame_disposed_, width, height); |
409 | if (dec->prev_iter_.dispose_method == WEBP_MUX_DISPOSE_BACKGROUND) { |
410 | ZeroFillFrameRect(dec->prev_frame_disposed_, width * NUM_CHANNELS, |
411 | dec->prev_iter_.x_offset, dec->prev_iter_.y_offset, |
412 | dec->prev_iter_.width, dec->prev_iter_.height); |
413 | } |
414 | ++dec->next_frame_; |
415 | |
416 | // All OK, fill in the values. |
417 | *buf_ptr = dec->curr_frame_; |
418 | *timestamp_ptr = timestamp; |
419 | return 1; |
420 | |
421 | Error: |
422 | WebPDemuxReleaseIterator(&iter); |
423 | return 0; |
424 | } |
425 | |
426 | int WebPAnimDecoderHasMoreFrames(const WebPAnimDecoder* dec) { |
427 | if (dec == NULL) return 0; |
428 | return (dec->next_frame_ <= (int)dec->info_.frame_count); |
429 | } |
430 | |
431 | void WebPAnimDecoderReset(WebPAnimDecoder* dec) { |
432 | if (dec != NULL) { |
433 | dec->prev_frame_timestamp_ = 0; |
434 | WebPDemuxReleaseIterator(&dec->prev_iter_); |
435 | memset(&dec->prev_iter_, 0, sizeof(dec->prev_iter_)); |
436 | dec->prev_frame_was_keyframe_ = 0; |
437 | dec->next_frame_ = 1; |
438 | } |
439 | } |
440 | |
441 | const WebPDemuxer* WebPAnimDecoderGetDemuxer(const WebPAnimDecoder* dec) { |
442 | if (dec == NULL) return NULL; |
443 | return dec->demux_; |
444 | } |
445 | |
446 | void WebPAnimDecoderDelete(WebPAnimDecoder* dec) { |
447 | if (dec != NULL) { |
448 | WebPDemuxReleaseIterator(&dec->prev_iter_); |
449 | WebPDemuxDelete(dec->demux_); |
450 | WebPSafeFree(dec->curr_frame_); |
451 | WebPSafeFree(dec->prev_frame_disposed_); |
452 | WebPSafeFree(dec); |
453 | } |
454 | } |
455 | |