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 "../webp/config.h" 15 #endif 16 17 #include <assert.h> 18 #include <string.h> 19 20 #include "../utils/utils.h" 21 #include "../webp/decode.h" 22 #include "../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 { 116 const int canvas_bytes = 117 dec->info_.canvas_width * NUM_CHANNELS * dec->info_.canvas_height; 118 // Note: calloc() because we fill frame with zeroes as well. 119 dec->curr_frame_ = WebPSafeCalloc(1ULL, canvas_bytes); 120 if (dec->curr_frame_ == NULL) goto Error; 121 dec->prev_frame_disposed_ = WebPSafeCalloc(1ULL, canvas_bytes); 122 if (dec->prev_frame_disposed_ == NULL) goto Error; 123 } 124 125 WebPAnimDecoderReset(dec); 126 127 return dec; 128 129 Error: 130 WebPAnimDecoderDelete(dec); 131 return NULL; 132 } 133 134 int WebPAnimDecoderGetInfo(const WebPAnimDecoder* dec, WebPAnimInfo* info) { 135 if (dec == NULL || info == NULL) return 0; 136 *info = dec->info_; 137 return 1; 138 } 139 140 // Returns true if the frame covers the full canvas. 141 static int IsFullFrame(int width, int height, int canvas_width, 142 int canvas_height) { 143 return (width == canvas_width && height == canvas_height); 144 } 145 146 // Clear the canvas to transparent. 147 static void ZeroFillCanvas(uint8_t* buf, uint32_t canvas_width, 148 uint32_t canvas_height) { 149 memset(buf, 0, canvas_width * NUM_CHANNELS * canvas_height); 150 } 151 152 // Clear given frame rectangle to transparent. 153 static void ZeroFillFrameRect(uint8_t* buf, int buf_stride, int x_offset, 154 int y_offset, int width, int height) { 155 int j; 156 assert(width * NUM_CHANNELS <= buf_stride); 157 buf += y_offset * buf_stride + x_offset * NUM_CHANNELS; 158 for (j = 0; j < height; ++j) { 159 memset(buf, 0, width * NUM_CHANNELS); 160 buf += buf_stride; 161 } 162 } 163 164 // Copy width * height pixels from 'src' to 'dst'. 165 static void CopyCanvas(const uint8_t* src, uint8_t* dst, 166 uint32_t width, uint32_t height) { 167 assert(src != NULL && dst != NULL); 168 memcpy(dst, src, width * NUM_CHANNELS * height); 169 } 170 171 // Returns true if the current frame is a key-frame. 172 static int IsKeyFrame(const WebPIterator* const curr, 173 const WebPIterator* const prev, 174 int prev_frame_was_key_frame, 175 int canvas_width, int canvas_height) { 176 if (curr->frame_num == 1) { 177 return 1; 178 } else if ((!curr->has_alpha || curr->blend_method == WEBP_MUX_NO_BLEND) && 179 IsFullFrame(curr->width, curr->height, 180 canvas_width, canvas_height)) { 181 return 1; 182 } else { 183 return (prev->dispose_method == WEBP_MUX_DISPOSE_BACKGROUND) && 184 (IsFullFrame(prev->width, prev->height, canvas_width, 185 canvas_height) || 186 prev_frame_was_key_frame); 187 } 188 } 189 190 191 // Blend a single channel of 'src' over 'dst', given their alpha channel values. 192 // 'src' and 'dst' are assumed to be NOT pre-multiplied by alpha. 193 static uint8_t BlendChannelNonPremult(uint32_t src, uint8_t src_a, 194 uint32_t dst, uint8_t dst_a, 195 uint32_t scale, int shift) { 196 const uint8_t src_channel = (src >> shift) & 0xff; 197 const uint8_t dst_channel = (dst >> shift) & 0xff; 198 const uint32_t blend_unscaled = src_channel * src_a + dst_channel * dst_a; 199 assert(blend_unscaled < (1ULL << 32) / scale); 200 return (blend_unscaled * scale) >> 24; 201 } 202 203 // Blend 'src' over 'dst' assuming they are NOT pre-multiplied by alpha. 204 static uint32_t BlendPixelNonPremult(uint32_t src, uint32_t dst) { 205 const uint8_t src_a = (src >> 24) & 0xff; 206 207 if (src_a == 0) { 208 return dst; 209 } else { 210 const uint8_t dst_a = (dst >> 24) & 0xff; 211 // This is the approximate integer arithmetic for the actual formula: 212 // dst_factor_a = (dst_a * (255 - src_a)) / 255. 213 const uint8_t dst_factor_a = (dst_a * (256 - src_a)) >> 8; 214 const uint8_t blend_a = src_a + dst_factor_a; 215 const uint32_t scale = (1UL << 24) / blend_a; 216 217 const uint8_t blend_r = 218 BlendChannelNonPremult(src, src_a, dst, dst_factor_a, scale, 0); 219 const uint8_t blend_g = 220 BlendChannelNonPremult(src, src_a, dst, dst_factor_a, scale, 8); 221 const uint8_t blend_b = 222 BlendChannelNonPremult(src, src_a, dst, dst_factor_a, scale, 16); 223 assert(src_a + dst_factor_a < 256); 224 225 return (blend_r << 0) | 226 (blend_g << 8) | 227 (blend_b << 16) | 228 ((uint32_t)blend_a << 24); 229 } 230 } 231 232 // Blend 'num_pixels' in 'src' over 'dst' assuming they are NOT pre-multiplied 233 // by alpha. 234 static void BlendPixelRowNonPremult(uint32_t* const src, 235 const uint32_t* const dst, int num_pixels) { 236 int i; 237 for (i = 0; i < num_pixels; ++i) { 238 const uint8_t src_alpha = (src[i] >> 24) & 0xff; 239 if (src_alpha != 0xff) { 240 src[i] = BlendPixelNonPremult(src[i], dst[i]); 241 } 242 } 243 } 244 245 // Individually multiply each channel in 'pix' by 'scale'. 246 static WEBP_INLINE uint32_t ChannelwiseMultiply(uint32_t pix, uint32_t scale) { 247 uint32_t mask = 0x00FF00FF; 248 uint32_t rb = ((pix & mask) * scale) >> 8; 249 uint32_t ag = ((pix >> 8) & mask) * scale; 250 return (rb & mask) | (ag & ~mask); 251 } 252 253 // Blend 'src' over 'dst' assuming they are pre-multiplied by alpha. 254 static uint32_t BlendPixelPremult(uint32_t src, uint32_t dst) { 255 const uint8_t src_a = (src >> 24) & 0xff; 256 return src + ChannelwiseMultiply(dst, 256 - src_a); 257 } 258 259 // Blend 'num_pixels' in 'src' over 'dst' assuming they are pre-multiplied by 260 // alpha. 261 static void BlendPixelRowPremult(uint32_t* const src, const uint32_t* const dst, 262 int num_pixels) { 263 int i; 264 for (i = 0; i < num_pixels; ++i) { 265 const uint8_t src_alpha = (src[i] >> 24) & 0xff; 266 if (src_alpha != 0xff) { 267 src[i] = BlendPixelPremult(src[i], dst[i]); 268 } 269 } 270 } 271 272 // Returns two ranges (<left, width> pairs) at row 'canvas_y', that belong to 273 // 'src' but not 'dst'. A point range is empty if the corresponding width is 0. 274 static void FindBlendRangeAtRow(const WebPIterator* const src, 275 const WebPIterator* const dst, int canvas_y, 276 int* const left1, int* const width1, 277 int* const left2, int* const width2) { 278 const int src_max_x = src->x_offset + src->width; 279 const int dst_max_x = dst->x_offset + dst->width; 280 const int dst_max_y = dst->y_offset + dst->height; 281 assert(canvas_y >= src->y_offset && canvas_y < (src->y_offset + src->height)); 282 *left1 = -1; 283 *width1 = 0; 284 *left2 = -1; 285 *width2 = 0; 286 287 if (canvas_y < dst->y_offset || canvas_y >= dst_max_y || 288 src->x_offset >= dst_max_x || src_max_x <= dst->x_offset) { 289 *left1 = src->x_offset; 290 *width1 = src->width; 291 return; 292 } 293 294 if (src->x_offset < dst->x_offset) { 295 *left1 = src->x_offset; 296 *width1 = dst->x_offset - src->x_offset; 297 } 298 299 if (src_max_x > dst_max_x) { 300 *left2 = dst_max_x; 301 *width2 = src_max_x - dst_max_x; 302 } 303 } 304 305 int WebPAnimDecoderGetNext(WebPAnimDecoder* dec, 306 uint8_t** buf_ptr, int* timestamp_ptr) { 307 WebPIterator iter; 308 uint32_t width; 309 uint32_t height; 310 int is_key_frame; 311 int timestamp; 312 BlendRowFunc blend_row; 313 314 if (dec == NULL || buf_ptr == NULL || timestamp_ptr == NULL) return 0; 315 if (!WebPAnimDecoderHasMoreFrames(dec)) return 0; 316 317 width = dec->info_.canvas_width; 318 height = dec->info_.canvas_height; 319 blend_row = dec->blend_func_; 320 321 // Get compressed frame. 322 if (!WebPDemuxGetFrame(dec->demux_, dec->next_frame_, &iter)) { 323 return 0; 324 } 325 timestamp = dec->prev_frame_timestamp_ + iter.duration; 326 327 // Initialize. 328 is_key_frame = IsKeyFrame(&iter, &dec->prev_iter_, 329 dec->prev_frame_was_keyframe_, width, height); 330 if (is_key_frame) { 331 ZeroFillCanvas(dec->curr_frame_, width, height); 332 } else { 333 CopyCanvas(dec->prev_frame_disposed_, dec->curr_frame_, width, height); 334 } 335 336 // Decode. 337 { 338 const uint8_t* in = iter.fragment.bytes; 339 const size_t in_size = iter.fragment.size; 340 const size_t out_offset = 341 (iter.y_offset * width + iter.x_offset) * NUM_CHANNELS; 342 WebPDecoderConfig* const config = &dec->config_; 343 WebPRGBABuffer* const buf = &config->output.u.RGBA; 344 buf->stride = NUM_CHANNELS * width; 345 buf->size = buf->stride * iter.height; 346 buf->rgba = dec->curr_frame_ + out_offset; 347 348 if (WebPDecode(in, in_size, config) != VP8_STATUS_OK) { 349 goto Error; 350 } 351 } 352 353 // During the decoding of current frame, we may have set some pixels to be 354 // transparent (i.e. alpha < 255). However, the value of each of these 355 // pixels should have been determined by blending it against the value of 356 // that pixel in the previous frame if blending method of is WEBP_MUX_BLEND. 357 if (iter.frame_num > 1 && iter.blend_method == WEBP_MUX_BLEND && 358 !is_key_frame) { 359 if (dec->prev_iter_.dispose_method == WEBP_MUX_DISPOSE_NONE) { 360 int y; 361 // Blend transparent pixels with pixels in previous canvas. 362 for (y = 0; y < iter.height; ++y) { 363 const size_t offset = 364 (iter.y_offset + y) * width + iter.x_offset; 365 blend_row((uint32_t*)dec->curr_frame_ + offset, 366 (uint32_t*)dec->prev_frame_disposed_ + offset, iter.width); 367 } 368 } else { 369 int y; 370 assert(dec->prev_iter_.dispose_method == WEBP_MUX_DISPOSE_BACKGROUND); 371 // We need to blend a transparent pixel with its value just after 372 // initialization. That is, blend it with: 373 // * Fully transparent pixel if it belongs to prevRect <-- No-op. 374 // * The pixel in the previous canvas otherwise <-- Need alpha-blending. 375 for (y = 0; y < iter.height; ++y) { 376 const int canvas_y = iter.y_offset + y; 377 int left1, width1, left2, width2; 378 FindBlendRangeAtRow(&iter, &dec->prev_iter_, canvas_y, &left1, &width1, 379 &left2, &width2); 380 if (width1 > 0) { 381 const size_t offset1 = canvas_y * width + left1; 382 blend_row((uint32_t*)dec->curr_frame_ + offset1, 383 (uint32_t*)dec->prev_frame_disposed_ + offset1, width1); 384 } 385 if (width2 > 0) { 386 const size_t offset2 = canvas_y * width + left2; 387 blend_row((uint32_t*)dec->curr_frame_ + offset2, 388 (uint32_t*)dec->prev_frame_disposed_ + offset2, width2); 389 } 390 } 391 } 392 } 393 394 // Update info of the previous frame and dispose it for the next iteration. 395 dec->prev_frame_timestamp_ = timestamp; 396 dec->prev_iter_ = iter; 397 dec->prev_frame_was_keyframe_ = is_key_frame; 398 CopyCanvas(dec->curr_frame_, dec->prev_frame_disposed_, width, height); 399 if (dec->prev_iter_.dispose_method == WEBP_MUX_DISPOSE_BACKGROUND) { 400 ZeroFillFrameRect(dec->prev_frame_disposed_, width * NUM_CHANNELS, 401 dec->prev_iter_.x_offset, dec->prev_iter_.y_offset, 402 dec->prev_iter_.width, dec->prev_iter_.height); 403 } 404 ++dec->next_frame_; 405 406 // All OK, fill in the values. 407 *buf_ptr = dec->curr_frame_; 408 *timestamp_ptr = timestamp; 409 return 1; 410 411 Error: 412 WebPDemuxReleaseIterator(&iter); 413 return 0; 414 } 415 416 int WebPAnimDecoderHasMoreFrames(const WebPAnimDecoder* dec) { 417 if (dec == NULL) return 0; 418 return (dec->next_frame_ <= (int)dec->info_.frame_count); 419 } 420 421 void WebPAnimDecoderReset(WebPAnimDecoder* dec) { 422 if (dec != NULL) { 423 dec->prev_frame_timestamp_ = 0; 424 memset(&dec->prev_iter_, 0, sizeof(dec->prev_iter_)); 425 dec->prev_frame_was_keyframe_ = 0; 426 dec->next_frame_ = 1; 427 } 428 } 429 430 const WebPDemuxer* WebPAnimDecoderGetDemuxer(const WebPAnimDecoder* dec) { 431 if (dec == NULL) return NULL; 432 return dec->demux_; 433 } 434 435 void WebPAnimDecoderDelete(WebPAnimDecoder* dec) { 436 if (dec != NULL) { 437 WebPDemuxDelete(dec->demux_); 438 WebPSafeFree(dec->curr_frame_); 439 WebPSafeFree(dec->prev_frame_disposed_); 440 WebPSafeFree(dec); 441 } 442 } 443
