go-libwebp

Experimental translation from libwebp to Go source.
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muxedit.c (22060B)


      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 // Set and delete APIs for mux.
     11 //
     12 // Authors: Urvang (urvang@google.com)
     13 //          Vikas (vikasa@google.com)
     14 
     15 #include <assert.h>
     16 #include <stddef.h>
     17 #include <string.h>
     18 
     19 #include "src/dec/vp8_dec.h"
     20 #include "src/mux/muxi.h"
     21 #include "src/utils/utils.h"
     22 #include "src/webp/format_constants.h"
     23 #include "src/webp/mux.h"
     24 #include "src/webp/mux_types.h"
     25 #include "src/webp/types.h"
     26 
     27 //------------------------------------------------------------------------------
     28 // Life of a mux object.
     29 
     30 static void MuxInit(WebPMux* const mux) {
     31   assert(mux != NULL);
     32   memset(mux, 0, sizeof(*mux));
     33   mux->canvas_width = 0;     // just to be explicit
     34   mux->canvas_height = 0;
     35 }
     36 
     37 WebPMux* WebPNewInternal(int version) {
     38   if (WEBP_ABI_IS_INCOMPATIBLE(version, WEBP_MUX_ABI_VERSION)) {
     39     return NULL;
     40   } else {
     41     WebPMux* const mux = (WebPMux*)WebPSafeMalloc(1ULL, sizeof(WebPMux));
     42     if (mux != NULL) MuxInit(mux);
     43     return mux;
     44   }
     45 }
     46 
     47 // Delete all images in 'wpi_list'.
     48 static void DeleteAllImages(WebPMuxImage** const wpi_list) {
     49   while (*wpi_list != NULL) {
     50     *wpi_list = MuxImageDelete(*wpi_list);
     51   }
     52 }
     53 
     54 static void MuxRelease(WebPMux* const mux) {
     55   assert(mux != NULL);
     56   DeleteAllImages(&mux->images);
     57   ChunkListDelete(&mux->vp8x);
     58   ChunkListDelete(&mux->iccp);
     59   ChunkListDelete(&mux->anim);
     60   ChunkListDelete(&mux->exif);
     61   ChunkListDelete(&mux->xmp);
     62   ChunkListDelete(&mux->unknown);
     63 }
     64 
     65 void WebPMuxDelete(WebPMux* mux) {
     66   if (mux != NULL) {
     67     MuxRelease(mux);
     68     WebPSafeFree(mux);
     69   }
     70 }
     71 
     72 //------------------------------------------------------------------------------
     73 // Helper method(s).
     74 
     75 // Handy MACRO, makes MuxSet() very symmetric to MuxGet().
     76 #define SWITCH_ID_LIST(INDEX, LIST)                                            \
     77   do {                                                                         \
     78     if (idx == (INDEX)) {                                                      \
     79       err = ChunkAssignData(&chunk, data, copy_data, tag);                     \
     80       if (err == WEBP_MUX_OK) {                                                \
     81         err = ChunkSetHead(&chunk, (LIST));                                    \
     82         if (err != WEBP_MUX_OK) ChunkRelease(&chunk);                          \
     83       }                                                                        \
     84       return err;                                                              \
     85     }                                                                          \
     86   } while (0)
     87 
     88 static WebPMuxError MuxSet(WebPMux* const mux, uint32_t tag,
     89                            const WebPData* const data, int copy_data) {
     90   WebPChunk chunk;
     91   WebPMuxError err = WEBP_MUX_NOT_FOUND;
     92   const CHUNK_INDEX idx = ChunkGetIndexFromTag(tag);
     93   assert(mux != NULL);
     94   assert(!IsWPI(kChunks[idx].id));
     95 
     96   ChunkInit(&chunk);
     97   SWITCH_ID_LIST(IDX_VP8X,    &mux->vp8x);
     98   SWITCH_ID_LIST(IDX_ICCP,    &mux->iccp);
     99   SWITCH_ID_LIST(IDX_ANIM,    &mux->anim);
    100   SWITCH_ID_LIST(IDX_EXIF,    &mux->exif);
    101   SWITCH_ID_LIST(IDX_XMP,     &mux->xmp);
    102   SWITCH_ID_LIST(IDX_UNKNOWN, &mux->unknown);
    103   return err;
    104 }
    105 #undef SWITCH_ID_LIST
    106 
    107 // Create data for frame given image data, offsets and duration.
    108 static WebPMuxError CreateFrameData(
    109     int width, int height, const WebPMuxFrameInfo* const info,
    110     WebPData* const frame) {
    111   uint8_t* frame_bytes;
    112   const size_t frame_size = kChunks[IDX_ANMF].size;
    113 
    114   assert(width > 0 && height > 0 && info->duration >= 0);
    115   assert(info->dispose_method == (info->dispose_method & 1));
    116   // Note: assertion on upper bounds is done in PutLE24().
    117 
    118   frame_bytes = (uint8_t*)WebPSafeMalloc(1ULL, frame_size);
    119   if (frame_bytes == NULL) return WEBP_MUX_MEMORY_ERROR;
    120 
    121   PutLE24(frame_bytes + 0, info->x_offset / 2);
    122   PutLE24(frame_bytes + 3, info->y_offset / 2);
    123 
    124   PutLE24(frame_bytes + 6, width - 1);
    125   PutLE24(frame_bytes + 9, height - 1);
    126   PutLE24(frame_bytes + 12, info->duration);
    127   frame_bytes[15] =
    128       (info->blend_method == WEBP_MUX_NO_BLEND ? 2 : 0) |
    129       (info->dispose_method == WEBP_MUX_DISPOSE_BACKGROUND ? 1 : 0);
    130 
    131   frame->bytes = frame_bytes;
    132   frame->size = frame_size;
    133   return WEBP_MUX_OK;
    134 }
    135 
    136 // Outputs image data given a bitstream. The bitstream can either be a
    137 // single-image WebP file or raw VP8/VP8L data.
    138 // Also outputs 'is_lossless' to be true if the given bitstream is lossless.
    139 static WebPMuxError GetImageData(const WebPData* const bitstream,
    140                                  WebPData* const image, WebPData* const alpha,
    141                                  int* const is_lossless) {
    142   WebPDataInit(alpha);  // Default: no alpha.
    143   if (bitstream->size < TAG_SIZE ||
    144       memcmp(bitstream->bytes, "RIFF", TAG_SIZE)) {
    145     // It is NOT webp file data. Return input data as is.
    146     *image = *bitstream;
    147   } else {
    148     // It is webp file data. Extract image data from it.
    149     const WebPMuxImage* wpi;
    150     WebPMux* const mux = WebPMuxCreate(bitstream, 0);
    151     if (mux == NULL) return WEBP_MUX_BAD_DATA;
    152     wpi = mux->images;
    153     assert(wpi != NULL && wpi->img != NULL);
    154     *image = wpi->img->data;
    155     if (wpi->alpha != NULL) {
    156       *alpha = wpi->alpha->data;
    157     }
    158     WebPMuxDelete(mux);
    159   }
    160   *is_lossless = VP8LCheckSignature(image->bytes, image->size);
    161   return WEBP_MUX_OK;
    162 }
    163 
    164 static WebPMuxError DeleteChunks(WebPChunk** chunk_list, uint32_t tag) {
    165   WebPMuxError err = WEBP_MUX_NOT_FOUND;
    166   assert(chunk_list);
    167   while (*chunk_list) {
    168     WebPChunk* const chunk = *chunk_list;
    169     if (chunk->tag == tag) {
    170       *chunk_list = ChunkDelete(chunk);
    171       err = WEBP_MUX_OK;
    172     } else {
    173       chunk_list = &chunk->next;
    174     }
    175   }
    176   return err;
    177 }
    178 
    179 static WebPMuxError MuxDeleteAllNamedData(WebPMux* const mux, uint32_t tag) {
    180   const WebPChunkId id = ChunkGetIdFromTag(tag);
    181   assert(mux != NULL);
    182   if (IsWPI(id)) return WEBP_MUX_INVALID_ARGUMENT;
    183   return DeleteChunks(MuxGetChunkListFromId(mux, id), tag);
    184 }
    185 
    186 //------------------------------------------------------------------------------
    187 // Set API(s).
    188 
    189 WebPMuxError WebPMuxSetChunk(WebPMux* mux, const char fourcc[4],
    190                              const WebPData* chunk_data, int copy_data) {
    191   uint32_t tag;
    192   WebPMuxError err;
    193   if (mux == NULL || fourcc == NULL || chunk_data == NULL ||
    194       chunk_data->bytes == NULL || chunk_data->size > MAX_CHUNK_PAYLOAD) {
    195     return WEBP_MUX_INVALID_ARGUMENT;
    196   }
    197   tag = ChunkGetTagFromFourCC(fourcc);
    198 
    199   // Delete existing chunk(s) with the same 'fourcc'.
    200   err = MuxDeleteAllNamedData(mux, tag);
    201   if (err != WEBP_MUX_OK && err != WEBP_MUX_NOT_FOUND) return err;
    202 
    203   // Add the given chunk.
    204   return MuxSet(mux, tag, chunk_data, copy_data);
    205 }
    206 
    207 // Creates a chunk from given 'data' and sets it as 1st chunk in 'chunk_list'.
    208 static WebPMuxError AddDataToChunkList(
    209     const WebPData* const data, int copy_data, uint32_t tag,
    210     WebPChunk** chunk_list) {
    211   WebPChunk chunk;
    212   WebPMuxError err;
    213   ChunkInit(&chunk);
    214   err = ChunkAssignData(&chunk, data, copy_data, tag);
    215   if (err != WEBP_MUX_OK) goto Err;
    216   err = ChunkSetHead(&chunk, chunk_list);
    217   if (err != WEBP_MUX_OK) goto Err;
    218   return WEBP_MUX_OK;
    219  Err:
    220   ChunkRelease(&chunk);
    221   return err;
    222 }
    223 
    224 // Extracts image & alpha data from the given bitstream and then sets wpi.alpha
    225 // and wpi.img appropriately.
    226 static WebPMuxError SetAlphaAndImageChunks(
    227     const WebPData* const bitstream, int copy_data, WebPMuxImage* const wpi) {
    228   int is_lossless = 0;
    229   WebPData image, alpha;
    230   WebPMuxError err = GetImageData(bitstream, &image, &alpha, &is_lossless);
    231   const int image_tag =
    232       is_lossless ? kChunks[IDX_VP8L].tag : kChunks[IDX_VP8].tag;
    233   if (err != WEBP_MUX_OK) return err;
    234   if (alpha.bytes != NULL) {
    235     err = AddDataToChunkList(&alpha, copy_data, kChunks[IDX_ALPHA].tag,
    236                              &wpi->alpha);
    237     if (err != WEBP_MUX_OK) return err;
    238   }
    239   err = AddDataToChunkList(&image, copy_data, image_tag, &wpi->img);
    240   if (err != WEBP_MUX_OK) return err;
    241   return MuxImageFinalize(wpi) ? WEBP_MUX_OK : WEBP_MUX_INVALID_ARGUMENT;
    242 }
    243 
    244 WebPMuxError WebPMuxSetImage(WebPMux* mux, const WebPData* bitstream,
    245                              int copy_data) {
    246   WebPMuxImage wpi;
    247   WebPMuxError err;
    248 
    249   if (mux == NULL || bitstream == NULL || bitstream->bytes == NULL ||
    250       bitstream->size > MAX_CHUNK_PAYLOAD) {
    251     return WEBP_MUX_INVALID_ARGUMENT;
    252   }
    253 
    254   if (mux->images != NULL) {
    255     // Only one 'simple image' can be added in mux. So, remove present images.
    256     DeleteAllImages(&mux->images);
    257   }
    258 
    259   MuxImageInit(&wpi);
    260   err = SetAlphaAndImageChunks(bitstream, copy_data, &wpi);
    261   if (err != WEBP_MUX_OK) goto Err;
    262 
    263   // Add this WebPMuxImage to mux.
    264   err = MuxImagePush(&wpi, &mux->images);
    265   if (err != WEBP_MUX_OK) goto Err;
    266 
    267   // All is well.
    268   return WEBP_MUX_OK;
    269 
    270  Err:  // Something bad happened.
    271   MuxImageRelease(&wpi);
    272   return err;
    273 }
    274 
    275 WebPMuxError WebPMuxPushFrame(WebPMux* mux, const WebPMuxFrameInfo* info,
    276                               int copy_data) {
    277   WebPMuxImage wpi;
    278   WebPMuxError err;
    279 
    280   if (mux == NULL || info == NULL) return WEBP_MUX_INVALID_ARGUMENT;
    281 
    282   if (info->id != WEBP_CHUNK_ANMF) return WEBP_MUX_INVALID_ARGUMENT;
    283 
    284   if (info->bitstream.bytes == NULL ||
    285       info->bitstream.size > MAX_CHUNK_PAYLOAD) {
    286     return WEBP_MUX_INVALID_ARGUMENT;
    287   }
    288 
    289   if (mux->images != NULL) {
    290     const WebPMuxImage* const image = mux->images;
    291     const uint32_t image_id = (image->header != NULL) ?
    292         ChunkGetIdFromTag(image->header->tag) : WEBP_CHUNK_IMAGE;
    293     if (image_id != info->id) {
    294       return WEBP_MUX_INVALID_ARGUMENT;  // Conflicting frame types.
    295     }
    296   }
    297 
    298   MuxImageInit(&wpi);
    299   err = SetAlphaAndImageChunks(&info->bitstream, copy_data, &wpi);
    300   if (err != WEBP_MUX_OK) goto Err;
    301   assert(wpi.img != NULL);  // As SetAlphaAndImageChunks() was successful.
    302 
    303   {
    304     WebPData frame;
    305     const uint32_t tag = kChunks[IDX_ANMF].tag;
    306     WebPMuxFrameInfo tmp = *info;
    307     tmp.x_offset &= ~1;  // Snap offsets to even.
    308     tmp.y_offset &= ~1;
    309     if (tmp.x_offset < 0 || tmp.x_offset >= MAX_POSITION_OFFSET ||
    310         tmp.y_offset < 0 || tmp.y_offset >= MAX_POSITION_OFFSET ||
    311         (tmp.duration < 0 || tmp.duration >= MAX_DURATION) ||
    312         tmp.dispose_method != (tmp.dispose_method & 1)) {
    313       err = WEBP_MUX_INVALID_ARGUMENT;
    314       goto Err;
    315     }
    316     err = CreateFrameData(wpi.width, wpi.height, &tmp, &frame);
    317     if (err != WEBP_MUX_OK) goto Err;
    318     // Add frame chunk (with copy_data = 1).
    319     err = AddDataToChunkList(&frame, 1, tag, &wpi.header);
    320     WebPDataClear(&frame);  // frame owned by wpi.header now.
    321     if (err != WEBP_MUX_OK) goto Err;
    322   }
    323 
    324   // Add this WebPMuxImage to mux.
    325   err = MuxImagePush(&wpi, &mux->images);
    326   if (err != WEBP_MUX_OK) goto Err;
    327 
    328   // All is well.
    329   return WEBP_MUX_OK;
    330 
    331  Err:  // Something bad happened.
    332   MuxImageRelease(&wpi);
    333   return err;
    334 }
    335 
    336 WebPMuxError WebPMuxSetAnimationParams(WebPMux* mux,
    337                                        const WebPMuxAnimParams* params) {
    338   WebPMuxError err;
    339   uint8_t data[ANIM_CHUNK_SIZE];
    340   const WebPData anim = { data, ANIM_CHUNK_SIZE };
    341 
    342   if (mux == NULL || params == NULL) return WEBP_MUX_INVALID_ARGUMENT;
    343   if (params->loop_count < 0 || params->loop_count >= MAX_LOOP_COUNT) {
    344     return WEBP_MUX_INVALID_ARGUMENT;
    345   }
    346 
    347   // Delete any existing ANIM chunk(s).
    348   err = MuxDeleteAllNamedData(mux, kChunks[IDX_ANIM].tag);
    349   if (err != WEBP_MUX_OK && err != WEBP_MUX_NOT_FOUND) return err;
    350 
    351   // Set the animation parameters.
    352   PutLE32(data, params->bgcolor);
    353   PutLE16(data + 4, params->loop_count);
    354   return MuxSet(mux, kChunks[IDX_ANIM].tag, &anim, 1);
    355 }
    356 
    357 WebPMuxError WebPMuxSetCanvasSize(WebPMux* mux,
    358                                   int width, int height) {
    359   WebPMuxError err;
    360   if (mux == NULL) {
    361     return WEBP_MUX_INVALID_ARGUMENT;
    362   }
    363   if (width < 0 || height < 0 ||
    364       width > MAX_CANVAS_SIZE || height > MAX_CANVAS_SIZE) {
    365     return WEBP_MUX_INVALID_ARGUMENT;
    366   }
    367   if (width * (uint64_t)height >= MAX_IMAGE_AREA) {
    368     return WEBP_MUX_INVALID_ARGUMENT;
    369   }
    370   if ((width * height) == 0 && (width | height) != 0) {
    371     // one of width / height is zero, but not both -> invalid!
    372     return WEBP_MUX_INVALID_ARGUMENT;
    373   }
    374   // If we already assembled a VP8X chunk, invalidate it.
    375   err = MuxDeleteAllNamedData(mux, kChunks[IDX_VP8X].tag);
    376   if (err != WEBP_MUX_OK && err != WEBP_MUX_NOT_FOUND) return err;
    377 
    378   mux->canvas_width = width;
    379   mux->canvas_height = height;
    380   return WEBP_MUX_OK;
    381 }
    382 
    383 //------------------------------------------------------------------------------
    384 // Delete API(s).
    385 
    386 WebPMuxError WebPMuxDeleteChunk(WebPMux* mux, const char fourcc[4]) {
    387   if (mux == NULL || fourcc == NULL) return WEBP_MUX_INVALID_ARGUMENT;
    388   return MuxDeleteAllNamedData(mux, ChunkGetTagFromFourCC(fourcc));
    389 }
    390 
    391 WebPMuxError WebPMuxDeleteFrame(WebPMux* mux, uint32_t nth) {
    392   if (mux == NULL) return WEBP_MUX_INVALID_ARGUMENT;
    393   return MuxImageDeleteNth(&mux->images, nth);
    394 }
    395 
    396 //------------------------------------------------------------------------------
    397 // Assembly of the WebP RIFF file.
    398 
    399 static WebPMuxError GetFrameInfo(
    400     const WebPChunk* const frame_chunk,
    401     int* const x_offset, int* const y_offset, int* const duration) {
    402   const WebPData* const data = &frame_chunk->data;
    403   const size_t expected_data_size = ANMF_CHUNK_SIZE;
    404   assert(frame_chunk->tag == kChunks[IDX_ANMF].tag);
    405   assert(frame_chunk != NULL);
    406   if (data->size != expected_data_size) return WEBP_MUX_INVALID_ARGUMENT;
    407 
    408   *x_offset = 2 * GetLE24(data->bytes + 0);
    409   *y_offset = 2 * GetLE24(data->bytes + 3);
    410   *duration = GetLE24(data->bytes + 12);
    411   return WEBP_MUX_OK;
    412 }
    413 
    414 static WebPMuxError GetImageInfo(const WebPMuxImage* const wpi,
    415                                  int* const x_offset, int* const y_offset,
    416                                  int* const duration,
    417                                  int* const width, int* const height) {
    418   const WebPChunk* const frame_chunk = wpi->header;
    419   WebPMuxError err;
    420   assert(wpi != NULL);
    421   assert(frame_chunk != NULL);
    422 
    423   // Get offsets and duration from ANMF chunk.
    424   err = GetFrameInfo(frame_chunk, x_offset, y_offset, duration);
    425   if (err != WEBP_MUX_OK) return err;
    426 
    427   // Get width and height from VP8/VP8L chunk.
    428   if (width != NULL) *width = wpi->width;
    429   if (height != NULL) *height = wpi->height;
    430   return WEBP_MUX_OK;
    431 }
    432 
    433 // Returns the tightest dimension for the canvas considering the image list.
    434 static WebPMuxError GetAdjustedCanvasSize(const WebPMux* const mux,
    435                                           int* const width, int* const height) {
    436   WebPMuxImage* wpi = NULL;
    437   assert(mux != NULL);
    438   assert(width != NULL && height != NULL);
    439 
    440   wpi = mux->images;
    441   assert(wpi != NULL);
    442   assert(wpi->img != NULL);
    443 
    444   if (wpi->next != NULL) {
    445     int max_x = 0, max_y = 0;
    446     // if we have a chain of wpi's, header is necessarily set
    447     assert(wpi->header != NULL);
    448     // Aggregate the bounding box for animation frames.
    449     for (; wpi != NULL; wpi = wpi->next) {
    450       int x_offset = 0, y_offset = 0, duration = 0, w = 0, h = 0;
    451       const WebPMuxError err = GetImageInfo(wpi, &x_offset, &y_offset,
    452                                             &duration, &w, &h);
    453       const int max_x_pos = x_offset + w;
    454       const int max_y_pos = y_offset + h;
    455       if (err != WEBP_MUX_OK) return err;
    456       assert(x_offset < MAX_POSITION_OFFSET);
    457       assert(y_offset < MAX_POSITION_OFFSET);
    458 
    459       if (max_x_pos > max_x) max_x = max_x_pos;
    460       if (max_y_pos > max_y) max_y = max_y_pos;
    461     }
    462     *width = max_x;
    463     *height = max_y;
    464   } else {
    465     // For a single image, canvas dimensions are same as image dimensions.
    466     *width = wpi->width;
    467     *height = wpi->height;
    468   }
    469   return WEBP_MUX_OK;
    470 }
    471 
    472 // VP8X format:
    473 // Total Size : 10,
    474 // Flags  : 4 bytes,
    475 // Width  : 3 bytes,
    476 // Height : 3 bytes.
    477 static WebPMuxError CreateVP8XChunk(WebPMux* const mux) {
    478   WebPMuxError err = WEBP_MUX_OK;
    479   uint32_t flags = 0;
    480   int width = 0;
    481   int height = 0;
    482   uint8_t data[VP8X_CHUNK_SIZE];
    483   const WebPData vp8x = { data, VP8X_CHUNK_SIZE };
    484   const WebPMuxImage* images = NULL;
    485 
    486   assert(mux != NULL);
    487   images = mux->images;  // First image.
    488   if (images == NULL || images->img == NULL ||
    489       images->img->data.bytes == NULL) {
    490     return WEBP_MUX_INVALID_ARGUMENT;
    491   }
    492 
    493   // If VP8X chunk(s) is(are) already present, remove them (and later add new
    494   // VP8X chunk with updated flags).
    495   err = MuxDeleteAllNamedData(mux, kChunks[IDX_VP8X].tag);
    496   if (err != WEBP_MUX_OK && err != WEBP_MUX_NOT_FOUND) return err;
    497 
    498   // Set flags.
    499   if (mux->iccp != NULL && mux->iccp->data.bytes != NULL) {
    500     flags |= ICCP_FLAG;
    501   }
    502   if (mux->exif != NULL && mux->exif->data.bytes != NULL) {
    503     flags |= EXIF_FLAG;
    504   }
    505   if (mux->xmp != NULL && mux->xmp->data.bytes != NULL) {
    506     flags |= XMP_FLAG;
    507   }
    508   if (images->header != NULL) {
    509     if (images->header->tag == kChunks[IDX_ANMF].tag) {
    510       // This is an image with animation.
    511       flags |= ANIMATION_FLAG;
    512     }
    513   }
    514   if (MuxImageCount(images, WEBP_CHUNK_ALPHA) > 0) {
    515     flags |= ALPHA_FLAG;  // Some images have an alpha channel.
    516   }
    517 
    518   err = GetAdjustedCanvasSize(mux, &width, &height);
    519   if (err != WEBP_MUX_OK) return err;
    520 
    521   if (width <= 0 || height <= 0) {
    522     return WEBP_MUX_INVALID_ARGUMENT;
    523   }
    524   if (width > MAX_CANVAS_SIZE || height > MAX_CANVAS_SIZE) {
    525     return WEBP_MUX_INVALID_ARGUMENT;
    526   }
    527 
    528   if (mux->canvas_width != 0 || mux->canvas_height != 0) {
    529     if (width > mux->canvas_width || height > mux->canvas_height) {
    530       return WEBP_MUX_INVALID_ARGUMENT;
    531     }
    532     width = mux->canvas_width;
    533     height = mux->canvas_height;
    534   }
    535 
    536   if (flags == 0 && mux->unknown == NULL) {
    537     // For simple file format, VP8X chunk should not be added.
    538     return WEBP_MUX_OK;
    539   }
    540 
    541   if (MuxHasAlpha(images)) {
    542     // This means some frames explicitly/implicitly contain alpha.
    543     // Note: This 'flags' update must NOT be done for a lossless image
    544     // without a VP8X chunk!
    545     flags |= ALPHA_FLAG;
    546   }
    547 
    548   PutLE32(data + 0, flags);   // VP8X chunk flags.
    549   PutLE24(data + 4, width - 1);   // canvas width.
    550   PutLE24(data + 7, height - 1);  // canvas height.
    551 
    552   return MuxSet(mux, kChunks[IDX_VP8X].tag, &vp8x, 1);
    553 }
    554 
    555 // Cleans up 'mux' by removing any unnecessary chunks.
    556 static WebPMuxError MuxCleanup(WebPMux* const mux) {
    557   int num_frames;
    558   int num_anim_chunks;
    559 
    560   // If we have an image with a single frame, and its rectangle
    561   // covers the whole canvas, convert it to a non-animated image
    562   // (to avoid writing ANMF chunk unnecessarily).
    563   WebPMuxError err = WebPMuxNumChunks(mux, kChunks[IDX_ANMF].id, &num_frames);
    564   if (err != WEBP_MUX_OK) return err;
    565   if (num_frames == 1) {
    566     WebPMuxImage* frame = NULL;
    567     err = MuxImageGetNth((const WebPMuxImage**)&mux->images, 1, &frame);
    568     if (err != WEBP_MUX_OK) return err;
    569     // We know that one frame does exist.
    570     assert(frame != NULL);
    571     if (frame->header != NULL &&
    572         ((mux->canvas_width == 0 && mux->canvas_height == 0) ||
    573          (frame->width == mux->canvas_width &&
    574           frame->height == mux->canvas_height))) {
    575       assert(frame->header->tag == kChunks[IDX_ANMF].tag);
    576       ChunkDelete(frame->header);  // Removes ANMF chunk.
    577       frame->header = NULL;
    578       num_frames = 0;
    579     }
    580   }
    581   // Remove ANIM chunk if this is a non-animated image.
    582   err = WebPMuxNumChunks(mux, kChunks[IDX_ANIM].id, &num_anim_chunks);
    583   if (err != WEBP_MUX_OK) return err;
    584   if (num_anim_chunks >= 1 && num_frames == 0) {
    585     err = MuxDeleteAllNamedData(mux, kChunks[IDX_ANIM].tag);
    586     if (err != WEBP_MUX_OK) return err;
    587   }
    588   return WEBP_MUX_OK;
    589 }
    590 
    591 // Total size of a list of images.
    592 static size_t ImageListDiskSize(const WebPMuxImage* wpi_list) {
    593   size_t size = 0;
    594   while (wpi_list != NULL) {
    595     size += MuxImageDiskSize(wpi_list);
    596     wpi_list = wpi_list->next;
    597   }
    598   return size;
    599 }
    600 
    601 // Write out the given list of images into 'dst'.
    602 static uint8_t* ImageListEmit(const WebPMuxImage* wpi_list, uint8_t* dst) {
    603   while (wpi_list != NULL) {
    604     dst = MuxImageEmit(wpi_list, dst);
    605     wpi_list = wpi_list->next;
    606   }
    607   return dst;
    608 }
    609 
    610 WebPMuxError WebPMuxAssemble(WebPMux* mux, WebPData* assembled_data) {
    611   size_t size = 0;
    612   uint8_t* data = NULL;
    613   uint8_t* dst = NULL;
    614   WebPMuxError err;
    615 
    616   if (assembled_data == NULL) {
    617     return WEBP_MUX_INVALID_ARGUMENT;
    618   }
    619   // Clean up returned data, in case something goes wrong.
    620   memset(assembled_data, 0, sizeof(*assembled_data));
    621 
    622   if (mux == NULL) {
    623     return WEBP_MUX_INVALID_ARGUMENT;
    624   }
    625 
    626   // Finalize mux.
    627   err = MuxCleanup(mux);
    628   if (err != WEBP_MUX_OK) return err;
    629   err = CreateVP8XChunk(mux);
    630   if (err != WEBP_MUX_OK) return err;
    631 
    632   // Allocate data.
    633   size = ChunkListDiskSize(mux->vp8x) + ChunkListDiskSize(mux->iccp)
    634        + ChunkListDiskSize(mux->anim) + ImageListDiskSize(mux->images)
    635        + ChunkListDiskSize(mux->exif) + ChunkListDiskSize(mux->xmp)
    636        + ChunkListDiskSize(mux->unknown) + RIFF_HEADER_SIZE;
    637 
    638   data = (uint8_t*)WebPSafeMalloc(1ULL, size);
    639   if (data == NULL) return WEBP_MUX_MEMORY_ERROR;
    640 
    641   // Emit header & chunks.
    642   dst = MuxEmitRiffHeader(data, size);
    643   dst = ChunkListEmit(mux->vp8x, dst);
    644   dst = ChunkListEmit(mux->iccp, dst);
    645   dst = ChunkListEmit(mux->anim, dst);
    646   dst = ImageListEmit(mux->images, dst);
    647   dst = ChunkListEmit(mux->exif, dst);
    648   dst = ChunkListEmit(mux->xmp, dst);
    649   dst = ChunkListEmit(mux->unknown, dst);
    650   assert(dst == data + size);
    651 
    652   // Validate mux.
    653   err = MuxValidate(mux);
    654   if (err != WEBP_MUX_OK) {
    655     WebPSafeFree(data);
    656     data = NULL;
    657     size = 0;
    658   }
    659 
    660   // Finalize data.
    661   assembled_data->bytes = data;
    662   assembled_data->size = size;
    663 
    664   return err;
    665 }
    666 
    667 //------------------------------------------------------------------------------