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FFmpeg/libavcodec/webp.c

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  1. /*

  2.  * WebP (.webp) image decoder

  3.  * Copyright (c) 2013 Aneesh Dogra <aneesh@sugarlabs.org>

  4.  * Copyright (c) 2013 Justin Ruggles <justin.ruggles@gmail.com>

  5.  *

  6.  * This file is part of Libav.

  7.  *

  8.  * Libav is free software; you can redistribute it and/or

  9.  * modify it under the terms of the GNU Lesser General Public

  10.  * License as published by the Free Software Foundation; either

  11.  * version 2.1 of the License, or (at your option) any later version.

  12.  *

  13.  * Libav is distributed in the hope that it will be useful,

  14.  * but WITHOUT ANY WARRANTY; without even the implied warranty of

  15.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

  16.  * Lesser General Public License for more details.

  17.  *

  18.  * You should have received a copy of the GNU Lesser General Public

  19.  * License along with Libav; if not, write to the Free Software

  20.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

  21.  */

  22. 

  23. /**

  24.  * @file

  25.  * WebP image decoder

  26.  *

  27.  * @author Aneesh Dogra <aneesh@sugarlabs.org>

  28.  * Container and Lossy decoding

  29.  *

  30.  * @author Justin Ruggles <justin.ruggles@gmail.com>

  31.  * Lossless decoder

  32.  * Compressed alpha for lossy

  33.  *

  34.  * Unimplemented:

  35.  *   - Animation

  36.  *   - ICC profile

  37.  *   - Exif and XMP metadata

  38.  */

  39. 

  40. #define BITSTREAM_READER_LE

  41. #include "libavutil/imgutils.h"

  42. #include "avcodec.h"

  43. #include "bytestream.h"

  44. #include "internal.h"

  45. #include "get_bits.h"

  46. #include "thread.h"

  47. #include "vp8.h"

  48. 

  49. #define VP8X_FLAG_ANIMATION             0x02

  50. #define VP8X_FLAG_XMP_METADATA          0x04

  51. #define VP8X_FLAG_EXIF_METADATA         0x08

  52. #define VP8X_FLAG_ALPHA                 0x10

  53. #define VP8X_FLAG_ICC                   0x20

  54. 

  55. #define MAX_PALETTE_SIZE                256

  56. #define MAX_CACHE_BITS                  11

  57. #define NUM_CODE_LENGTH_CODES           19

  58. #define HUFFMAN_CODES_PER_META_CODE     5

  59. #define NUM_LITERAL_CODES               256

  60. #define NUM_LENGTH_CODES                24

  61. #define NUM_DISTANCE_CODES              40

  62. #define NUM_SHORT_DISTANCES             120

  63. #define MAX_HUFFMAN_CODE_LENGTH         15

  64. 

  65. static const uint16_t alphabet_sizes[HUFFMAN_CODES_PER_META_CODE] = {

  66.     NUM_LITERAL_CODES + NUM_LENGTH_CODES,

  67.     NUM_LITERAL_CODES, NUM_LITERAL_CODES, NUM_LITERAL_CODES,

  68.     NUM_DISTANCE_CODES

  69. };

  70. 

  71. static const uint8_t code_length_code_order[NUM_CODE_LENGTH_CODES] = {

  72.     17, 18, 0, 1, 2, 3, 4, 5, 16, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15

  73. };

  74. 

  75. static const int8_t lz77_distance_offsets[NUM_SHORT_DISTANCES][2] = {

  76.     {  0, 1 }, {  1, 0 }, {  1, 1 }, { -1, 1 }, {  0, 2 }, {  2, 0 }, {  1, 2 }, { -1, 2 },

  77.     {  2, 1 }, { -2, 1 }, {  2, 2 }, { -2, 2 }, {  0, 3 }, {  3, 0 }, {  1, 3 }, { -1, 3 },

  78.     {  3, 1 }, { -3, 1 }, {  2, 3 }, { -2, 3 }, {  3, 2 }, { -3, 2 }, {  0, 4 }, {  4, 0 },

  79.     {  1, 4 }, { -1, 4 }, {  4, 1 }, { -4, 1 }, {  3, 3 }, { -3, 3 }, {  2, 4 }, { -2, 4 },

  80.     {  4, 2 }, { -4, 2 }, {  0, 5 }, {  3, 4 }, { -3, 4 }, {  4, 3 }, { -4, 3 }, {  5, 0 },

  81.     {  1, 5 }, { -1, 5 }, {  5, 1 }, { -5, 1 }, {  2, 5 }, { -2, 5 }, {  5, 2 }, { -5, 2 },

  82.     {  4, 4 }, { -4, 4 }, {  3, 5 }, { -3, 5 }, {  5, 3 }, { -5, 3 }, {  0, 6 }, {  6, 0 },

  83.     {  1, 6 }, { -1, 6 }, {  6, 1 }, { -6, 1 }, {  2, 6 }, { -2, 6 }, {  6, 2 }, { -6, 2 },

  84.     {  4, 5 }, { -4, 5 }, {  5, 4 }, { -5, 4 }, {  3, 6 }, { -3, 6 }, {  6, 3 }, { -6, 3 },

  85.     {  0, 7 }, {  7, 0 }, {  1, 7 }, { -1, 7 }, {  5, 5 }, { -5, 5 }, {  7, 1 }, { -7, 1 },

  86.     {  4, 6 }, { -4, 6 }, {  6, 4 }, { -6, 4 }, {  2, 7 }, { -2, 7 }, {  7, 2 }, { -7, 2 },

  87.     {  3, 7 }, { -3, 7 }, {  7, 3 }, { -7, 3 }, {  5, 6 }, { -5, 6 }, {  6, 5 }, { -6, 5 },

  88.     {  8, 0 }, {  4, 7 }, { -4, 7 }, {  7, 4 }, { -7, 4 }, {  8, 1 }, {  8, 2 }, {  6, 6 },

  89.     { -6, 6 }, {  8, 3 }, {  5, 7 }, { -5, 7 }, {  7, 5 }, { -7, 5 }, {  8, 4 }, {  6, 7 },

  90.     { -6, 7 }, {  7, 6 }, { -7, 6 }, {  8, 5 }, {  7, 7 }, { -7, 7 }, {  8, 6 }, {  8, 7 }

  91. };

  92. 

  93. enum AlphaCompression {

  94.     ALPHA_COMPRESSION_NONE,

  95.     ALPHA_COMPRESSION_VP8L,

  96. };

  97. 

  98. enum AlphaFilter {

  99.     ALPHA_FILTER_NONE,

  100.     ALPHA_FILTER_HORIZONTAL,

  101.     ALPHA_FILTER_VERTICAL,

  102.     ALPHA_FILTER_GRADIENT,

  103. };

  104. 

  105. enum TransformType {

  106.     PREDICTOR_TRANSFORM      = 0,

  107.     COLOR_TRANSFORM          = 1,

  108.     SUBTRACT_GREEN           = 2,

  109.     COLOR_INDEXING_TRANSFORM = 3,

  110. };

  111. 

  112. enum PredictionMode {

  113.     PRED_MODE_BLACK,

  114.     PRED_MODE_L,

  115.     PRED_MODE_T,

  116.     PRED_MODE_TR,

  117.     PRED_MODE_TL,

  118.     PRED_MODE_AVG_T_AVG_L_TR,

  119.     PRED_MODE_AVG_L_TL,

  120.     PRED_MODE_AVG_L_T,

  121.     PRED_MODE_AVG_TL_T,

  122.     PRED_MODE_AVG_T_TR,

  123.     PRED_MODE_AVG_AVG_L_TL_AVG_T_TR,

  124.     PRED_MODE_SELECT,

  125.     PRED_MODE_ADD_SUBTRACT_FULL,

  126.     PRED_MODE_ADD_SUBTRACT_HALF,

  127. };

  128. 

  129. enum HuffmanIndex {

  130.     HUFF_IDX_GREEN = 0,

  131.     HUFF_IDX_RED   = 1,

  132.     HUFF_IDX_BLUE  = 2,

  133.     HUFF_IDX_ALPHA = 3,

  134.     HUFF_IDX_DIST  = 4

  135. };

  136. 

  137. /* The structure of WebP lossless is an optional series of transformation data,

  138.  * followed by the primary image. The primary image also optionally contains

  139.  * an entropy group mapping if there are multiple entropy groups. There is a

  140.  * basic image type called an "entropy coded image" that is used for all of

  141.  * these. The type of each entropy coded image is referred to by the

  142.  * specification as its role. */

  143. enum ImageRole {

  144.     /* Primary Image: Stores the actual pixels of the image. */

  145.     IMAGE_ROLE_ARGB,

  146. 

  147.     /* Entropy Image: Defines which Huffman group to use for different areas of

  148.      *                the primary image. */

  149.     IMAGE_ROLE_ENTROPY,

  150. 

  151.     /* Predictors: Defines which predictor type to use for different areas of

  152.      *             the primary image. */

  153.     IMAGE_ROLE_PREDICTOR,

  154. 

  155.     /* Color Transform Data: Defines the color transformation for different

  156.      *                       areas of the primary image. */

  157.     IMAGE_ROLE_COLOR_TRANSFORM,

  158. 

  159.     /* Color Index: Stored as an image of height == 1. */

  160.     IMAGE_ROLE_COLOR_INDEXING,

  161. 

  162.     IMAGE_ROLE_NB,

  163. };

  164. 

  165. typedef struct HuffReader {

  166.     VLC vlc;                            /* Huffman decoder context */

  167.     int simple;                         /* whether to use simple mode */

  168.     int nb_symbols;                     /* number of coded symbols */

  169.     uint16_t simple_symbols[2];         /* symbols for simple mode */

  170. } HuffReader;

  171. 

  172. typedef struct ImageContext {

  173.     enum ImageRole role;                /* role of this image */

  174.     AVFrame *frame;                     /* AVFrame for data */

  175.     int color_cache_bits;               /* color cache size, log2 */

  176.     uint32_t *color_cache;              /* color cache data */

  177.     int nb_huffman_groups;              /* number of huffman groups */

  178.     HuffReader *huffman_groups;         /* reader for each huffman group */

  179.     int size_reduction;                 /* relative size compared to primary image, log2 */

  180.     int is_alpha_primary;

  181. } ImageContext;

  182. 

  183. typedef struct WebPContext {

  184.     VP8Context v;                       /* VP8 Context used for lossy decoding */

  185.     GetBitContext gb;                   /* bitstream reader for main image chunk */

  186.     AVFrame *alpha_frame;               /* AVFrame for alpha data decompressed from VP8L */

  187.     AVCodecContext *avctx;              /* parent AVCodecContext */

  188.     int initialized;                    /* set once the VP8 context is initialized */

  189.     int has_alpha;                      /* has a separate alpha chunk */

  190.     enum AlphaCompression alpha_compression; /* compression type for alpha chunk */

  191.     enum AlphaFilter alpha_filter;      /* filtering method for alpha chunk */

  192.     uint8_t *alpha_data;                /* alpha chunk data */

  193.     int alpha_data_size;                /* alpha chunk data size */

  194.     int width;                          /* image width */

  195.     int height;                         /* image height */

  196.     int lossless;                       /* indicates lossless or lossy */

  197. 

  198.     int nb_transforms;                  /* number of transforms */

  199.     enum TransformType transforms[4];   /* transformations used in the image, in order */

  200.     int reduced_width;                  /* reduced width for index image, if applicable */

  201.     int nb_huffman_groups;              /* number of huffman groups in the primary image */

  202.     ImageContext image[IMAGE_ROLE_NB];  /* image context for each role */

  203. } WebPContext;

  204. 

  205. #define GET_PIXEL(frame, x, y) \

  206.     ((frame)->data[0] + (y) * frame->linesize[0] + 4 * (x))

  207. 

  208. #define GET_PIXEL_COMP(frame, x, y, c) \

  209.     (*((frame)->data[0] + (y) * frame->linesize[0] + 4 * (x) + c))

  210. 

  211. static void image_ctx_free(ImageContext *img)

  212. {

  213.     int i, j;

  214. 

  215.     av_free(img->color_cache);

  216.     if (img->role != IMAGE_ROLE_ARGB && !img->is_alpha_primary)

  217.         av_frame_free(&img->frame);

  218.     if (img->huffman_groups) {

  219.         for (i = 0; i < img->nb_huffman_groups; i++) {

  220.             for (j = 0; j < HUFFMAN_CODES_PER_META_CODE; j++)

  221.                 ff_free_vlc(&img->huffman_groups[i * HUFFMAN_CODES_PER_META_CODE + j].vlc);

  222.         }

  223.         av_free(img->huffman_groups);

  224.     }

  225.     memset(img, 0, sizeof(*img));

  226. }

  227. 

  228. 

  229. /* Differs from get_vlc2() in the following ways:

  230.  *   - codes are bit-reversed

  231.  *   - assumes 8-bit table to make reversal simpler

  232.  *   - assumes max depth of 2 since the max code length for WebP is 15

  233.  */

  234. static av_always_inline int webp_get_vlc(GetBitContext *gb, VLC_TYPE (*table)[2])

  235. {

  236.     int n, nb_bits;

  237.     unsigned int index;

  238.     int code;

  239. 

  240.     OPEN_READER(re, gb);

  241.     UPDATE_CACHE(re, gb);

  242. 

  243.     index = SHOW_UBITS(re, gb, 8);

  244.     index = ff_reverse[index];

  245.     code  = table[index][0];

  246.     n     = table[index][1];

  247. 

  248.     if (n < 0) {

  249.         LAST_SKIP_BITS(re, gb, 8);

  250.         UPDATE_CACHE(re, gb);

  251. 

  252.         nb_bits = -n;

  253. 

  254.         index = SHOW_UBITS(re, gb, nb_bits);

  255.         index = (ff_reverse[index] >> (8 - nb_bits)) + code;

  256.         code  = table[index][0];

  257.         n     = table[index][1];

  258.     }

  259.     SKIP_BITS(re, gb, n);

  260. 

  261.     CLOSE_READER(re, gb);

  262. 

  263.     return code;

  264. }

  265. 

  266. static int huff_reader_get_symbol(HuffReader *r, GetBitContext *gb)

  267. {

  268.     if (r->simple) {

  269.         if (r->nb_symbols == 1)

  270.             return r->simple_symbols[0];

  271.         else

  272.             return r->simple_symbols[get_bits1(gb)];

  273.     } else

  274.         return webp_get_vlc(gb, r->vlc.table);

  275. }

  276. 

  277. static int huff_reader_build_canonical(HuffReader *r, int *code_lengths,

  278.                                        int alphabet_size)

  279. {

  280.     int len, sym, code, ret;

  281.     int max_code_length = 0;

  282.     uint16_t *codes;

  283. 

  284.     for (sym = 0; sym < alphabet_size; sym++)

  285.         max_code_length = FFMAX(max_code_length, code_lengths[sym]);

  286. 

  287.     if (max_code_length == 0 || max_code_length > MAX_HUFFMAN_CODE_LENGTH)

  288.         return AVERROR(EINVAL);

  289. 

  290.     codes = av_malloc(alphabet_size * sizeof(*codes));

  291.     if (!codes)

  292.         return AVERROR(ENOMEM);

  293. 

  294.     code = 0;

  295.     r->nb_symbols = 0;

  296.     for (len = 1; len <= max_code_length; len++) {

  297.         for (sym = 0; sym < alphabet_size; sym++) {

  298.             if (code_lengths[sym] != len)

  299.                 continue;

  300.             codes[sym] = code++;

  301.             r->nb_symbols++;

  302.         }

  303.         code <<= 1;

  304.     }

  305.     if (!r->nb_symbols) {

  306.         av_free(codes);

  307.         return AVERROR_INVALIDDATA;

  308.     }

  309. 

  310.     ret = init_vlc(&r->vlc, 8, alphabet_size,

  311.                    code_lengths, sizeof(*code_lengths), sizeof(*code_lengths),

  312.                    codes, sizeof(*codes), sizeof(*codes), 0);

  313.     if (ret < 0) {

  314.         av_free(codes);

  315.         return ret;

  316.     }

  317.     r->simple = 0;

  318. 

  319.     av_free(codes);

  320.     return 0;

  321. }

  322. 

  323. static void read_huffman_code_simple(WebPContext *s, HuffReader *hc)

  324. {

  325.     hc->nb_symbols = get_bits1(&s->gb) + 1;

  326. 

  327.     if (get_bits1(&s->gb))

  328.         hc->simple_symbols[0] = get_bits(&s->gb, 8);

  329.     else

  330.         hc->simple_symbols[0] = get_bits1(&s->gb);

  331. 

  332.     if (hc->nb_symbols == 2)

  333.         hc->simple_symbols[1] = get_bits(&s->gb, 8);

  334. 

  335.     hc->simple = 1;

  336. }

  337. 

  338. static int read_huffman_code_normal(WebPContext *s, HuffReader *hc,

  339.                                     int alphabet_size)

  340. {

  341.     HuffReader code_len_hc = { { 0 }, 0, 0, { 0 } };

  342.     int *code_lengths = NULL;

  343.     int code_length_code_lengths[NUM_CODE_LENGTH_CODES] = { 0 };

  344.     int i, symbol, max_symbol, prev_code_len, ret;

  345.     int num_codes = 4 + get_bits(&s->gb, 4);

  346. 

  347.     if (num_codes > NUM_CODE_LENGTH_CODES)

  348.         return AVERROR_INVALIDDATA;

  349. 

  350.     for (i = 0; i < num_codes; i++)

  351.         code_length_code_lengths[code_length_code_order[i]] = get_bits(&s->gb, 3);

  352. 

  353.     ret = huff_reader_build_canonical(&code_len_hc, code_length_code_lengths,

  354.                                       NUM_CODE_LENGTH_CODES);

  355.     if (ret < 0)

  356.         goto finish;

  357. 

  358.     code_lengths = av_mallocz_array(alphabet_size, sizeof(*code_lengths));

  359.     if (!code_lengths) {

  360.         ret = AVERROR(ENOMEM);

  361.         goto finish;

  362.     }

  363. 

  364.     if (get_bits1(&s->gb)) {

  365.         int bits   = 2 + 2 * get_bits(&s->gb, 3);

  366.         max_symbol = 2 + get_bits(&s->gb, bits);

  367.         if (max_symbol > alphabet_size) {

  368.             av_log(s->avctx, AV_LOG_ERROR, "max symbol %d > alphabet size %d\n",

  369.                    max_symbol, alphabet_size);

  370.             ret = AVERROR_INVALIDDATA;

  371.             goto finish;

  372.         }

  373.     } else {

  374.         max_symbol = alphabet_size;

  375.     }

  376. 

  377.     prev_code_len = 8;

  378.     symbol        = 0;

  379.     while (symbol < alphabet_size) {

  380.         int code_len;

  381. 

  382.         if (!max_symbol--)

  383.             break;

  384.         code_len = huff_reader_get_symbol(&code_len_hc, &s->gb);

  385.         if (code_len < 16) {

  386.             /* Code length code [0..15] indicates literal code lengths. */

  387.             code_lengths[symbol++] = code_len;

  388.             if (code_len)

  389.                 prev_code_len = code_len;

  390.         } else {

  391.             int repeat = 0, length = 0;

  392.             switch (code_len) {

  393.             case 16:

  394.                 /* Code 16 repeats the previous non-zero value [3..6] times,

  395.                  * i.e., 3 + ReadBits(2) times. If code 16 is used before a

  396.                  * non-zero value has been emitted, a value of 8 is repeated. */

  397.                 repeat = 3 + get_bits(&s->gb, 2);

  398.                 length = prev_code_len;

  399.                 break;

  400.             case 17:

  401.                 /* Code 17 emits a streak of zeros [3..10], i.e.,

  402.                  * 3 + ReadBits(3) times. */

  403.                 repeat = 3 + get_bits(&s->gb, 3);

  404.                 break;

  405.             case 18:

  406.                 /* Code 18 emits a streak of zeros of length [11..138], i.e.,

  407.                  * 11 + ReadBits(7) times. */

  408.                 repeat = 11 + get_bits(&s->gb, 7);

  409.                 break;

  410.             }

  411.             if (symbol + repeat > alphabet_size) {

  412.                 av_log(s->avctx, AV_LOG_ERROR,

  413.                        "invalid symbol %d + repeat %d > alphabet size %d\n",

  414.                        symbol, repeat, alphabet_size);

  415.                 ret = AVERROR_INVALIDDATA;

  416.                 goto finish;

  417.             }

  418.             while (repeat-- > 0)

  419.                 code_lengths[symbol++] = length;

  420.         }

  421.     }

  422. 

  423.     ret = huff_reader_build_canonical(hc, code_lengths, alphabet_size);

  424. 

  425. finish:

  426.     ff_free_vlc(&code_len_hc.vlc);

  427.     av_free(code_lengths);

  428.     return ret;

  429. }

  430. 

  431. static int decode_entropy_coded_image(WebPContext *s, enum ImageRole role,

  432.                                       int w, int h);

  433. 

  434. #define PARSE_BLOCK_SIZE(w, h) do {                                         \

  435.     block_bits = get_bits(&s->gb, 3) + 2;                                   \

  436.     blocks_w   = FFALIGN((w), 1 << block_bits) >> block_bits;               \

  437.     blocks_h   = FFALIGN((h), 1 << block_bits) >> block_bits;               \

  438. } while (0)

  439. 

  440. static int decode_entropy_image(WebPContext *s)

  441. {

  442.     ImageContext *img;

  443.     int ret, block_bits, width, blocks_w, blocks_h, x, y, max;

  444. 

  445.     width = s->width;

  446.     if (s->reduced_width > 0)

  447.         width = s->reduced_width;

  448. 

  449.     PARSE_BLOCK_SIZE(width, s->height);

  450. 

  451.     ret = decode_entropy_coded_image(s, IMAGE_ROLE_ENTROPY, blocks_w, blocks_h);

  452.     if (ret < 0)

  453.         return ret;

  454. 

  455.     img = &s->image[IMAGE_ROLE_ENTROPY];

  456.     img->size_reduction = block_bits;

  457. 

  458.     /* the number of huffman groups is determined by the maximum group number

  459.      * coded in the entropy image */

  460.     max = 0;

  461.     for (y = 0; y < img->frame->height; y++) {

  462.         for (x = 0; x < img->frame->width; x++) {

  463.             int p = GET_PIXEL_COMP(img->frame, x, y, 2);

  464.             max = FFMAX(max, p);

  465.         }

  466.     }

  467.     s->nb_huffman_groups = max + 1;

  468. 

  469.     return 0;

  470. }

  471. 

  472. static int parse_transform_predictor(WebPContext *s)

  473. {

  474.     int block_bits, blocks_w, blocks_h, ret;

  475. 

  476.     PARSE_BLOCK_SIZE(s->width, s->height);

  477. 

  478.     ret = decode_entropy_coded_image(s, IMAGE_ROLE_PREDICTOR, blocks_w,

  479.                                      blocks_h);

  480.     if (ret < 0)

  481.         return ret;

  482. 

  483.     s->image[IMAGE_ROLE_PREDICTOR].size_reduction = block_bits;

  484. 

  485.     return 0;

  486. }

  487. 

  488. static int parse_transform_color(WebPContext *s)

  489. {

  490.     int block_bits, blocks_w, blocks_h, ret;

  491. 

  492.     PARSE_BLOCK_SIZE(s->width, s->height);

  493. 

  494.     ret = decode_entropy_coded_image(s, IMAGE_ROLE_COLOR_TRANSFORM, blocks_w,

  495.                                      blocks_h);

  496.     if (ret < 0)

  497.         return ret;

  498. 

  499.     s->image[IMAGE_ROLE_COLOR_TRANSFORM].size_reduction = block_bits;

  500. 

  501.     return 0;

  502. }

  503. 

  504. static int parse_transform_color_indexing(WebPContext *s)

  505. {

  506.     ImageContext *img;

  507.     int width_bits, index_size, ret, x;

  508.     uint8_t *ct;

  509. 

  510.     index_size = get_bits(&s->gb, 8) + 1;

  511. 

  512.     if (index_size <= 2)

  513.         width_bits = 3;

  514.     else if (index_size <= 4)

  515.         width_bits = 2;

  516.     else if (index_size <= 16)

  517.         width_bits = 1;

  518.     else

  519.         width_bits = 0;

  520. 

  521.     ret = decode_entropy_coded_image(s, IMAGE_ROLE_COLOR_INDEXING,

  522.                                      index_size, 1);

  523.     if (ret < 0)

  524.         return ret;

  525. 

  526.     img = &s->image[IMAGE_ROLE_COLOR_INDEXING];

  527.     img->size_reduction = width_bits;

  528.     if (width_bits > 0)

  529.         s->reduced_width = (s->width + ((1 << width_bits) - 1)) >> width_bits;

  530. 

  531.     /* color index values are delta-coded */

  532.     ct  = img->frame->data[0] + 4;

  533.     for (x = 4; x < img->frame->width * 4; x++, ct++)

  534.         ct[0] += ct[-4];

  535. 

  536.     return 0;

  537. }

  538. 

  539. static HuffReader *get_huffman_group(WebPContext *s, ImageContext *img,

  540.                                      int x, int y)

  541. {

  542.     ImageContext *gimg = &s->image[IMAGE_ROLE_ENTROPY];

  543.     int group = 0;

  544. 

  545.     if (gimg->size_reduction > 0) {

  546.         int group_x = x >> gimg->size_reduction;

  547.         int group_y = y >> gimg->size_reduction;

  548.         group       = GET_PIXEL_COMP(gimg->frame, group_x, group_y, 2);

  549.     }

  550. 

  551.     return &img->huffman_groups[group * HUFFMAN_CODES_PER_META_CODE];

  552. }

  553. 

  554. static av_always_inline void color_cache_put(ImageContext *img, uint32_t c)

  555. {

  556.     uint32_t cache_idx = (0x1E35A7BD * c) >> (32 - img->color_cache_bits);

  557.     img->color_cache[cache_idx] = c;

  558. }

  559. 

  560. static int decode_entropy_coded_image(WebPContext *s, enum ImageRole role,

  561.                                       int w, int h)

  562. {

  563.     ImageContext *img;

  564.     HuffReader *hg;

  565.     int i, j, ret, x, y, width;

  566. 

  567.     img       = &s->image[role];

  568.     img->role = role;

  569. 

  570.     if (!img->frame) {

  571.         img->frame = av_frame_alloc();

  572.         if (!img->frame)

  573.             return AVERROR(ENOMEM);

  574.     }

  575. 

  576.     img->frame->format = AV_PIX_FMT_ARGB;

  577.     img->frame->width  = w;

  578.     img->frame->height = h;

  579. 

  580.     if (role == IMAGE_ROLE_ARGB && !img->is_alpha_primary) {

  581.         ThreadFrame pt = { .f = img->frame };

  582.         ret = ff_thread_get_buffer(s->avctx, &pt, 0);

  583.     } else

  584.         ret = av_frame_get_buffer(img->frame, 1);

  585.     if (ret < 0)

  586.         return ret;

  587. 

  588.     if (get_bits1(&s->gb)) {

  589.         img->color_cache_bits = get_bits(&s->gb, 4);

  590.         if (img->color_cache_bits < 1 || img->color_cache_bits > 11) {

  591.             av_log(s->avctx, AV_LOG_ERROR, "invalid color cache bits: %d\n",

  592.                    img->color_cache_bits);

  593.             return AVERROR_INVALIDDATA;

  594.         }

  595.         img->color_cache = av_mallocz_array(1 << img->color_cache_bits,

  596.                                             sizeof(*img->color_cache));

  597.         if (!img->color_cache)

  598.             return AVERROR(ENOMEM);

  599.     } else {

  600.         img->color_cache_bits = 0;

  601.     }

  602. 

  603.     img->nb_huffman_groups = 1;

  604.     if (role == IMAGE_ROLE_ARGB && get_bits1(&s->gb)) {

  605.         ret = decode_entropy_image(s);

  606.         if (ret < 0)

  607.             return ret;

  608.         img->nb_huffman_groups = s->nb_huffman_groups;

  609.     }

  610.     img->huffman_groups = av_mallocz_array(img->nb_huffman_groups *

  611.                                            HUFFMAN_CODES_PER_META_CODE,

  612.                                            sizeof(*img->huffman_groups));

  613.     if (!img->huffman_groups)

  614.         return AVERROR(ENOMEM);

  615. 

  616.     for (i = 0; i < img->nb_huffman_groups; i++) {

  617.         hg = &img->huffman_groups[i * HUFFMAN_CODES_PER_META_CODE];

  618.         for (j = 0; j < HUFFMAN_CODES_PER_META_CODE; j++) {

  619.             int alphabet_size = alphabet_sizes[j];

  620.             if (!j && img->color_cache_bits > 0)

  621.                 alphabet_size += 1 << img->color_cache_bits;

  622. 

  623.             if (get_bits1(&s->gb)) {

  624.                 read_huffman_code_simple(s, &hg[j]);

  625.             } else {

  626.                 ret = read_huffman_code_normal(s, &hg[j], alphabet_size);

  627.                 if (ret < 0)

  628.                     return ret;

  629.             }

  630.         }

  631.     }

  632. 

  633.     width = img->frame->width;

  634.     if (role == IMAGE_ROLE_ARGB && s->reduced_width > 0)

  635.         width = s->reduced_width;

  636. 

  637.     x = 0; y = 0;

  638.     while (y < img->frame->height) {

  639.         int v;

  640. 

  641.         hg = get_huffman_group(s, img, x, y);

  642.         v = huff_reader_get_symbol(&hg[HUFF_IDX_GREEN], &s->gb);

  643.         if (v < NUM_LITERAL_CODES) {

  644.             /* literal pixel values */

  645.             uint8_t *p = GET_PIXEL(img->frame, x, y);

  646.             p[2] = v;

  647.             p[1] = huff_reader_get_symbol(&hg[HUFF_IDX_RED],   &s->gb);

  648.             p[3] = huff_reader_get_symbol(&hg[HUFF_IDX_BLUE],  &s->gb);

  649.             p[0] = huff_reader_get_symbol(&hg[HUFF_IDX_ALPHA], &s->gb);

  650.             if (img->color_cache_bits)

  651.                 color_cache_put(img, AV_RB32(p));

  652.             x++;

  653.             if (x == width) {

  654.                 x = 0;

  655.                 y++;

  656.             }

  657.         } else if (v < NUM_LITERAL_CODES + NUM_LENGTH_CODES) {

  658.             /* LZ77 backwards mapping */

  659.             int prefix_code, length, distance, ref_x, ref_y;

  660. 

  661.             /* parse length and distance */

  662.             prefix_code = v - NUM_LITERAL_CODES;

  663.             if (prefix_code < 4) {

  664.                 length = prefix_code + 1;

  665.             } else {

  666.                 int extra_bits = (prefix_code - 2) >> 1;

  667.                 int offset     = 2 + (prefix_code & 1) << extra_bits;

  668.                 length = offset + get_bits(&s->gb, extra_bits) + 1;

  669.             }

  670.             prefix_code = huff_reader_get_symbol(&hg[HUFF_IDX_DIST], &s->gb);

  671.             if (prefix_code < 4) {

  672.                 distance = prefix_code + 1;

  673.             } else {

  674.                 int extra_bits = prefix_code - 2 >> 1;

  675.                 int offset     = 2 + (prefix_code & 1) << extra_bits;

  676.                 distance = offset + get_bits(&s->gb, extra_bits) + 1;

  677.             }

  678. 

  679.             /* find reference location */

  680.             if (distance <= NUM_SHORT_DISTANCES) {

  681.                 int xi = lz77_distance_offsets[distance - 1][0];

  682.                 int yi = lz77_distance_offsets[distance - 1][1];

  683.                 distance = FFMAX(1, xi + yi * width);

  684.             } else {

  685.                 distance -= NUM_SHORT_DISTANCES;

  686.             }

  687.             ref_x = x;

  688.             ref_y = y;

  689.             if (distance <= x) {

  690.                 ref_x -= distance;

  691.                 distance = 0;

  692.             } else {

  693.                 ref_x = 0;

  694.                 distance -= x;

  695.             }

  696.             while (distance >= width) {

  697.                 ref_y--;

  698.                 distance -= width;

  699.             }

  700.             if (distance > 0) {

  701.                 ref_x = width - distance;

  702.                 ref_y--;

  703.             }

  704.             ref_x = FFMAX(0, ref_x);

  705.             ref_y = FFMAX(0, ref_y);

  706. 

  707.             /* copy pixels

  708.              * source and dest regions can overlap and wrap lines, so just

  709.              * copy per-pixel */

  710.             for (i = 0; i < length; i++) {

  711.                 uint8_t *p_ref = GET_PIXEL(img->frame, ref_x, ref_y);

  712.                 uint8_t *p     = GET_PIXEL(img->frame,     x,     y);

  713. 

  714.                 AV_COPY32(p, p_ref);

  715.                 if (img->color_cache_bits)

  716.                     color_cache_put(img, AV_RB32(p));

  717.                 x++;

  718.                 ref_x++;

  719.                 if (x == width) {

  720.                     x = 0;

  721.                     y++;

  722.                 }

  723.                 if (ref_x == width) {

  724.                     ref_x = 0;

  725.                     ref_y++;

  726.                 }

  727.                 if (y == img->frame->height || ref_y == img->frame->height)

  728.                     break;

  729.             }

  730.         } else {

  731.             /* read from color cache */

  732.             uint8_t *p = GET_PIXEL(img->frame, x, y);

  733.             int cache_idx = v - (NUM_LITERAL_CODES + NUM_LENGTH_CODES);

  734. 

  735.             if (!img->color_cache_bits) {

  736.                 av_log(s->avctx, AV_LOG_ERROR, "color cache not found\n");

  737.                 return AVERROR_INVALIDDATA;

  738.             }

  739.             if (cache_idx >= 1 << img->color_cache_bits) {

  740.                 av_log(s->avctx, AV_LOG_ERROR,

  741.                        "color cache index out-of-bounds\n");

  742.                 return AVERROR_INVALIDDATA;

  743.             }

  744.             AV_WB32(p, img->color_cache[cache_idx]);

  745.             x++;

  746.             if (x == width) {

  747.                 x = 0;

  748.                 y++;

  749.             }

  750.         }

  751.     }

  752. 

  753.     return 0;

  754. }

  755. 

  756. /* PRED_MODE_BLACK */

  757. static void inv_predict_0(uint8_t *p, const uint8_t *p_l, const uint8_t *p_tl,

  758.                           const uint8_t *p_t, const uint8_t *p_tr)

  759. {

  760.     AV_WB32(p, 0xFF000000);

  761. }

  762. 

  763. /* PRED_MODE_L */

  764. static void inv_predict_1(uint8_t *p, const uint8_t *p_l, const uint8_t *p_tl,

  765.                           const uint8_t *p_t, const uint8_t *p_tr)

  766. {

  767.     AV_COPY32(p, p_l);

  768. }

  769. 

  770. /* PRED_MODE_T */

  771. static void inv_predict_2(uint8_t *p, const uint8_t *p_l, const uint8_t *p_tl,

  772.                           const uint8_t *p_t, const uint8_t *p_tr)

  773. {

  774.     AV_COPY32(p, p_t);

  775. }

  776. 

  777. /* PRED_MODE_TR */

  778. static void inv_predict_3(uint8_t *p, const uint8_t *p_l, const uint8_t *p_tl,

  779.                           const uint8_t *p_t, const uint8_t *p_tr)

  780. {

  781.     AV_COPY32(p, p_tr);

  782. }

  783. 

  784. /* PRED_MODE_TL */

  785. static void inv_predict_4(uint8_t *p, const uint8_t *p_l, const uint8_t *p_tl,

  786.                           const uint8_t *p_t, const uint8_t *p_tr)

  787. {

  788.     AV_COPY32(p, p_tl);

  789. }

  790. 

  791. /* PRED_MODE_AVG_T_AVG_L_TR */

  792. static void inv_predict_5(uint8_t *p, const uint8_t *p_l, const uint8_t *p_tl,

  793.                           const uint8_t *p_t, const uint8_t *p_tr)

  794. {

  795.     p[0] = p_t[0] + (p_l[0] + p_tr[0] >> 1) >> 1;

  796.     p[1] = p_t[1] + (p_l[1] + p_tr[1] >> 1) >> 1;

  797.     p[2] = p_t[2] + (p_l[2] + p_tr[2] >> 1) >> 1;

  798.     p[3] = p_t[3] + (p_l[3] + p_tr[3] >> 1) >> 1;

  799. }

  800. 

  801. /* PRED_MODE_AVG_L_TL */

  802. static void inv_predict_6(uint8_t *p, const uint8_t *p_l, const uint8_t *p_tl,

  803.                           const uint8_t *p_t, const uint8_t *p_tr)

  804. {

  805.     p[0] = p_l[0] + p_tl[0] >> 1;

  806.     p[1] = p_l[1] + p_tl[1] >> 1;

  807.     p[2] = p_l[2] + p_tl[2] >> 1;

  808.     p[3] = p_l[3] + p_tl[3] >> 1;

  809. }

  810. 

  811. /* PRED_MODE_AVG_L_T */

  812. static void inv_predict_7(uint8_t *p, const uint8_t *p_l, const uint8_t *p_tl,

  813.                           const uint8_t *p_t, const uint8_t *p_tr)

  814. {

  815.     p[0] = p_l[0] + p_t[0] >> 1;

  816.     p[1] = p_l[1] + p_t[1] >> 1;

  817.     p[2] = p_l[2] + p_t[2] >> 1;

  818.     p[3] = p_l[3] + p_t[3] >> 1;

  819. }

  820. 

  821. /* PRED_MODE_AVG_TL_T */

  822. static void inv_predict_8(uint8_t *p, const uint8_t *p_l, const uint8_t *p_tl,

  823.                           const uint8_t *p_t, const uint8_t *p_tr)

  824. {

  825.     p[0] = p_tl[0] + p_t[0] >> 1;

  826.     p[1] = p_tl[1] + p_t[1] >> 1;

  827.     p[2] = p_tl[2] + p_t[2] >> 1;

  828.     p[3] = p_tl[3] + p_t[3] >> 1;

  829. }

  830. 

  831. /* PRED_MODE_AVG_T_TR */

  832. static void inv_predict_9(uint8_t *p, const uint8_t *p_l, const uint8_t *p_tl,

  833.                           const uint8_t *p_t, const uint8_t *p_tr)

  834. {

  835.     p[0] = p_t[0] + p_tr[0] >> 1;

  836.     p[1] = p_t[1] + p_tr[1] >> 1;

  837.     p[2] = p_t[2] + p_tr[2] >> 1;

  838.     p[3] = p_t[3] + p_tr[3] >> 1;

  839. }

  840. 

  841. /* PRED_MODE_AVG_AVG_L_TL_AVG_T_TR */

  842. static void inv_predict_10(uint8_t *p, const uint8_t *p_l, const uint8_t *p_tl,

  843.                            const uint8_t *p_t, const uint8_t *p_tr)

  844. {

  845.     p[0] = (p_l[0] + p_tl[0] >> 1) + (p_t[0] + p_tr[0] >> 1) >> 1;

  846.     p[1] = (p_l[1] + p_tl[1] >> 1) + (p_t[1] + p_tr[1] >> 1) >> 1;

  847.     p[2] = (p_l[2] + p_tl[2] >> 1) + (p_t[2] + p_tr[2] >> 1) >> 1;

  848.     p[3] = (p_l[3] + p_tl[3] >> 1) + (p_t[3] + p_tr[3] >> 1) >> 1;

  849. }

  850. 

  851. /* PRED_MODE_SELECT */

  852. static void inv_predict_11(uint8_t *p, const uint8_t *p_l, const uint8_t *p_tl,

  853.                            const uint8_t *p_t, const uint8_t *p_tr)

  854. {

  855.     int diff = (FFABS(p_l[0] - p_tl[0]) - FFABS(p_t[0] - p_tl[0])) +

  856.                (FFABS(p_l[1] - p_tl[1]) - FFABS(p_t[1] - p_tl[1])) +

  857.                (FFABS(p_l[2] - p_tl[2]) - FFABS(p_t[2] - p_tl[2])) +

  858.                (FFABS(p_l[3] - p_tl[3]) - FFABS(p_t[3] - p_tl[3]));

  859.     if (diff <= 0)

  860.         AV_COPY32(p, p_t);

  861.     else

  862.         AV_COPY32(p, p_l);

  863. }

  864. 

  865. /* PRED_MODE_ADD_SUBTRACT_FULL */

  866. static void inv_predict_12(uint8_t *p, const uint8_t *p_l, const uint8_t *p_tl,

  867.                            const uint8_t *p_t, const uint8_t *p_tr)

  868. {

  869.     p[0] = av_clip_uint8(p_l[0] + p_t[0] - p_tl[0]);

  870.     p[1] = av_clip_uint8(p_l[1] + p_t[1] - p_tl[1]);

  871.     p[2] = av_clip_uint8(p_l[2] + p_t[2] - p_tl[2]);

  872.     p[3] = av_clip_uint8(p_l[3] + p_t[3] - p_tl[3]);

  873. }

  874. 

  875. static av_always_inline uint8_t clamp_add_subtract_half(int a, int b, int c)

  876. {

  877.     int d = a + b >> 1;

  878.     return av_clip_uint8(d + (d - c) / 2);

  879. }

  880. 

  881. /* PRED_MODE_ADD_SUBTRACT_HALF */

  882. static void inv_predict_13(uint8_t *p, const uint8_t *p_l, const uint8_t *p_tl,

  883.                            const uint8_t *p_t, const uint8_t *p_tr)

  884. {

  885.     p[0] = clamp_add_subtract_half(p_l[0], p_t[0], p_tl[0]);

  886.     p[1] = clamp_add_subtract_half(p_l[1], p_t[1], p_tl[1]);

  887.     p[2] = clamp_add_subtract_half(p_l[2], p_t[2], p_tl[2]);

  888.     p[3] = clamp_add_subtract_half(p_l[3], p_t[3], p_tl[3]);

  889. }

  890. 

  891. typedef void (*inv_predict_func)(uint8_t *p, const uint8_t *p_l,

  892.                                  const uint8_t *p_tl, const uint8_t *p_t,

  893.                                  const uint8_t *p_tr);

  894. 

  895. static const inv_predict_func inverse_predict[14] = {

  896.     inv_predict_0,  inv_predict_1,  inv_predict_2,  inv_predict_3,

  897.     inv_predict_4,  inv_predict_5,  inv_predict_6,  inv_predict_7,

  898.     inv_predict_8,  inv_predict_9,  inv_predict_10, inv_predict_11,

  899.     inv_predict_12, inv_predict_13,

  900. };

  901. 

  902. static void inverse_prediction(AVFrame *frame, enum PredictionMode m, int x, int y)

  903. {

  904.     uint8_t *dec, *p_l, *p_tl, *p_t, *p_tr;

  905.     uint8_t p[4];

  906. 

  907.     dec  = GET_PIXEL(frame, x,     y);

  908.     p_l  = GET_PIXEL(frame, x - 1, y);

  909.     p_tl = GET_PIXEL(frame, x - 1, y - 1);

  910.     p_t  = GET_PIXEL(frame, x,     y - 1);

  911.     if (x == frame->width - 1)

  912.         p_tr = GET_PIXEL(frame, 0, y);

  913.     else

  914.         p_tr = GET_PIXEL(frame, x + 1, y - 1);

  915. 

  916.     inverse_predict[m](p, p_l, p_tl, p_t, p_tr);

  917. 

  918.     dec[0] += p[0];

  919.     dec[1] += p[1];

  920.     dec[2] += p[2];

  921.     dec[3] += p[3];

  922. }

  923. 

  924. static int apply_predictor_transform(WebPContext *s)

  925. {

  926.     ImageContext *img  = &s->image[IMAGE_ROLE_ARGB];

  927.     ImageContext *pimg = &s->image[IMAGE_ROLE_PREDICTOR];

  928.     int x, y;

  929. 

  930.     for (y = 0; y < img->frame->height; y++) {

  931.         for (x = 0; x < img->frame->width; x++) {

  932.             int tx = x >> pimg->size_reduction;

  933.             int ty = y >> pimg->size_reduction;

  934.             enum PredictionMode m = GET_PIXEL_COMP(pimg->frame, tx, ty, 2);

  935. 

  936.             if (x == 0) {

  937.                 if (y == 0)

  938.                     m = PRED_MODE_BLACK;

  939.                 else

  940.                     m = PRED_MODE_T;

  941.             } else if (y == 0)

  942.                 m = PRED_MODE_L;

  943. 

  944.             if (m > 13) {

  945.                 av_log(s->avctx, AV_LOG_ERROR,

  946.                        "invalid predictor mode: %d\n", m);

  947.                 return AVERROR_INVALIDDATA;

  948.             }

  949.             inverse_prediction(img->frame, m, x, y);

  950.         }

  951.     }

  952.     return 0;

  953. }

  954. 

  955. static av_always_inline uint8_t color_transform_delta(uint8_t color_pred,

  956.                                                       uint8_t color)

  957. {

  958.     return (int)ff_u8_to_s8(color_pred) * ff_u8_to_s8(color) >> 5;

  959. }

  960. 

  961. static int apply_color_transform(WebPContext *s)

  962. {

  963.     ImageContext *img, *cimg;

  964.     int x, y, cx, cy;

  965.     uint8_t *p, *cp;

  966. 

  967.     img  = &s->image[IMAGE_ROLE_ARGB];

  968.     cimg = &s->image[IMAGE_ROLE_COLOR_TRANSFORM];

  969. 

  970.     for (y = 0; y < img->frame->height; y++) {

  971.         for (x = 0; x < img->frame->width; x++) {

  972.             cx = x >> cimg->size_reduction;

  973.             cy = y >> cimg->size_reduction;

  974.             cp = GET_PIXEL(cimg->frame, cx, cy);

  975.             p  = GET_PIXEL(img->frame,   x,  y);

  976. 

  977.             p[1] += color_transform_delta(cp[3], p[2]);

  978.             p[3] += color_transform_delta(cp[2], p[2]) +

  979.                     color_transform_delta(cp[1], p[1]);

  980.         }

  981.     }

  982.     return 0;

  983. }

  984. 

  985. static int apply_subtract_green_transform(WebPContext *s)

  986. {

  987.     int x, y;

  988.     ImageContext *img = &s->image[IMAGE_ROLE_ARGB];

  989. 

  990.     for (y = 0; y < img->frame->height; y++) {

  991.         for (x = 0; x < img->frame->width; x++) {

  992.             uint8_t *p = GET_PIXEL(img->frame, x, y);

  993.             p[1] += p[2];

  994.             p[3] += p[2];

  995.         }

  996.     }

  997.     return 0;

  998. }

  999. 

  1000. static int apply_color_indexing_transform(WebPContext *s)

  1001. {

  1002.     ImageContext *img;

  1003.     ImageContext *pal;

  1004.     int i, x, y;

  1005.     uint8_t *p, *pi;

  1006. 

  1007.     img = &s->image[IMAGE_ROLE_ARGB];

  1008.     pal = &s->image[IMAGE_ROLE_COLOR_INDEXING];

  1009. 

  1010.     if (pal->size_reduction > 0) {

  1011.         GetBitContext gb_g;

  1012.         uint8_t *line;

  1013.         int pixel_bits = 8 >> pal->size_reduction;

  1014. 

  1015.         line = av_malloc(img->frame->linesize[0]);

  1016.         if (!line)

  1017.             return AVERROR(ENOMEM);

  1018. 

  1019.         for (y = 0; y < img->frame->height; y++) {

  1020.             p = GET_PIXEL(img->frame, 0, y);

  1021.             memcpy(line, p, img->frame->linesize[0]);

  1022.             init_get_bits(&gb_g, line, img->frame->linesize[0] * 8);

  1023.             skip_bits(&gb_g, 16);

  1024.             i = 0;

  1025.             for (x = 0; x < img->frame->width; x++) {

  1026.                 p    = GET_PIXEL(img->frame, x, y);

  1027.                 p[2] = get_bits(&gb_g, pixel_bits);

  1028.                 i++;

  1029.                 if (i == 1 << pal->size_reduction) {

  1030.                     skip_bits(&gb_g, 24);

  1031.                     i = 0;

  1032.                 }

  1033.             }

  1034.         }

  1035.         av_free(line);

  1036.     }

  1037. 

  1038.     for (y = 0; y < img->frame->height; y++) {

  1039.         for (x = 0; x < img->frame->width; x++) {

  1040.             p = GET_PIXEL(img->frame, x, y);

  1041.             i = p[2];

  1042.             if (i >= pal->frame->width) {

  1043.                 av_log(s->avctx, AV_LOG_ERROR, "invalid palette index %d\n", i);

  1044.                 return AVERROR_INVALIDDATA;

  1045.             }

  1046.             pi = GET_PIXEL(pal->frame, i, 0);

  1047.             AV_COPY32(p, pi);

  1048.         }

  1049.     }

  1050. 

  1051.     return 0;

  1052. }

  1053. 

  1054. static int vp8_lossless_decode_frame(AVCodecContext *avctx, AVFrame *p,

  1055.                                      int *got_frame, uint8_t *data_start,

  1056.                                      unsigned int data_size, int is_alpha_chunk)

  1057. {

  1058.     WebPContext *s = avctx->priv_data;

  1059.     int w, h, ret, i;

  1060. 

  1061.     if (!is_alpha_chunk) {

  1062.         s->lossless = 1;

  1063.         avctx->pix_fmt = AV_PIX_FMT_ARGB;

  1064.     }

  1065. 

  1066.     ret = init_get_bits(&s->gb, data_start, data_size * 8);

  1067.     if (ret < 0)

  1068.         return ret;

  1069. 

  1070.     if (!is_alpha_chunk) {

  1071.         if (get_bits(&s->gb, 8) != 0x2F) {

  1072.             av_log(avctx, AV_LOG_ERROR, "Invalid WebP Lossless signature\n");

  1073.             return AVERROR_INVALIDDATA;

  1074.         }

  1075. 

  1076.         w = get_bits(&s->gb, 14) + 1;

  1077.         h = get_bits(&s->gb, 14) + 1;

  1078.         if (s->width && s->width != w) {

  1079.             av_log(avctx, AV_LOG_WARNING, "Width mismatch. %d != %d\n",

  1080.                    s->width, w);

  1081.         }

  1082.         s->width = w;

  1083.         if (s->height && s->height != h) {

  1084.             av_log(avctx, AV_LOG_WARNING, "Height mismatch. %d != %d\n",

  1085.                    s->width, w);

  1086.         }

  1087.         s->height = h;

  1088.         ret = av_image_check_size(s->width, s->height, 0, avctx);

  1089.         if (ret < 0)

  1090.             return ret;

  1091.         avcodec_set_dimensions(avctx, s->width, s->height);

  1092. 

  1093.         s->has_alpha = get_bits1(&s->gb);

  1094. 

  1095.         if (get_bits(&s->gb, 3) != 0x0) {

  1096.             av_log(avctx, AV_LOG_ERROR, "Invalid WebP Lossless version\n");

  1097.             return AVERROR_INVALIDDATA;

  1098.         }

  1099.     } else {

  1100.         if (!s->width || !s->height)

  1101.             return AVERROR_BUG;

  1102.         w = s->width;

  1103.         h = s->height;

  1104.     }

  1105. 

  1106.     /* parse transformations */

  1107.     s->nb_transforms = 0;

  1108.     s->reduced_width = 0;

  1109.     while (get_bits1(&s->gb)) {

  1110.         enum TransformType transform = get_bits(&s->gb, 2);

  1111.         s->transforms[s->nb_transforms++] = transform;

  1112.         switch (transform) {

  1113.         case PREDICTOR_TRANSFORM:

  1114.             ret = parse_transform_predictor(s);

  1115.             break;

  1116.         case COLOR_TRANSFORM:

  1117.             ret = parse_transform_color(s);

  1118.             break;

  1119.         case COLOR_INDEXING_TRANSFORM:

  1120.             ret = parse_transform_color_indexing(s);

  1121.             break;

  1122.         }

  1123.         if (ret < 0)

  1124.             goto free_and_return;

  1125.     }

  1126. 

  1127.     /* decode primary image */

  1128.     s->image[IMAGE_ROLE_ARGB].frame = p;

  1129.     if (is_alpha_chunk)

  1130.         s->image[IMAGE_ROLE_ARGB].is_alpha_primary = 1;

  1131.     ret = decode_entropy_coded_image(s, IMAGE_ROLE_ARGB, w, h);

  1132.     if (ret < 0) {

  1133.         av_frame_free(&p);

  1134.         goto free_and_return;

  1135.     }

  1136. 

  1137.     /* apply transformations */

  1138.     for (i = s->nb_transforms - 1; i >= 0; i--) {

  1139.         switch (s->transforms[i]) {

  1140.         case PREDICTOR_TRANSFORM:

  1141.             ret = apply_predictor_transform(s);

  1142.             break;

  1143.         case COLOR_TRANSFORM:

  1144.             ret = apply_color_transform(s);

  1145.             break;

  1146.         case SUBTRACT_GREEN:

  1147.             ret = apply_subtract_green_transform(s);

  1148.             break;

  1149.         case COLOR_INDEXING_TRANSFORM:

  1150.             ret = apply_color_indexing_transform(s);

  1151.             break;

  1152.         }

  1153.         if (ret < 0) {

  1154.             av_frame_free(&p);

  1155.             goto free_and_return;

  1156.         }

  1157.     }

  1158. 

  1159.     *got_frame   = 1;

  1160.     p->pict_type = AV_PICTURE_TYPE_I;

  1161.     p->key_frame = 1;

  1162.     ret          = data_size;

  1163. 

  1164. free_and_return:

  1165.     for (i = 0; i < IMAGE_ROLE_NB; i++)

  1166.         image_ctx_free(&s->image[i]);

  1167. 

  1168.     return ret;

  1169. }

  1170. 

  1171. static void alpha_inverse_prediction(AVFrame *frame, enum AlphaFilter m)

  1172. {

  1173.     int x, y, ls;

  1174.     uint8_t *dec;

  1175. 

  1176.     ls = frame->linesize[3];

  1177. 

  1178.     /* filter first row using horizontal filter */

  1179.     dec = frame->data[3] + 1;

  1180.     for (x = 1; x < frame->width; x++, dec++)

  1181.         *dec += *(dec - 1);

  1182. 

  1183.     /* filter first column using vertical filter */

  1184.     dec = frame->data[3] + ls;

  1185.     for (y = 1; y < frame->height; y++, dec += ls)

  1186.         *dec += *(dec - ls);

  1187. 

  1188.     /* filter the rest using the specified filter */

  1189.     switch (m) {

  1190.     case ALPHA_FILTER_HORIZONTAL:

  1191.         for (y = 1; y < frame->height; y++) {

  1192.             dec = frame->data[3] + y * ls + 1;

  1193.             for (x = 1; x < frame->width; x++, dec++)

  1194.                 *dec += *(dec - 1);

  1195.         }

  1196.         break;

  1197.     case ALPHA_FILTER_VERTICAL:

  1198.         for (y = 1; y < frame->height; y++) {

  1199.             dec = frame->data[3] + y * ls + 1;

  1200.             for (x = 1; x < frame->width; x++, dec++)

  1201.                 *dec += *(dec - ls);

  1202.         }

  1203.         break;

  1204.     case ALPHA_FILTER_GRADIENT:

  1205.         for (y = 1; y < frame->height; y++) {

  1206.             dec = frame->data[3] + y * ls + 1;

  1207.             for (x = 1; x < frame->width; x++, dec++)

  1208.                 dec[0] += av_clip_uint8(*(dec - 1) + *(dec - ls) - *(dec - ls - 1));

  1209.         }

  1210.         break;

  1211.     }

  1212. }

  1213. 

  1214. static int vp8_lossy_decode_alpha(AVCodecContext *avctx, AVFrame *p,

  1215.                                   uint8_t *data_start,

  1216.                                   unsigned int data_size)

  1217. {

  1218.     WebPContext *s = avctx->priv_data;

  1219.     int x, y, ret;

  1220. 

  1221.     if (s->alpha_compression == ALPHA_COMPRESSION_NONE) {

  1222.         GetByteContext gb;

  1223. 

  1224.         bytestream2_init(&gb, data_start, data_size);

  1225.         for (y = 0; y < s->height; y++)

  1226.             bytestream2_get_buffer(&gb, p->data[3] + p->linesize[3] * y,

  1227.                                    s->width);

  1228.     } else if (s->alpha_compression == ALPHA_COMPRESSION_VP8L) {

  1229.         uint8_t *ap, *pp;

  1230.         int alpha_got_frame = 0;

  1231. 

  1232.         s->alpha_frame = av_frame_alloc();

  1233.         if (!s->alpha_frame)

  1234.             return AVERROR(ENOMEM);

  1235. 

  1236.         ret = vp8_lossless_decode_frame(avctx, s->alpha_frame, &alpha_got_frame,

  1237.                                         data_start, data_size, 1);

  1238.         if (ret < 0) {

  1239.             av_frame_free(&s->alpha_frame);

  1240.             return ret;

  1241.         }

  1242.         if (!alpha_got_frame) {

  1243.             av_frame_free(&s->alpha_frame);

  1244.             return AVERROR_INVALIDDATA;

  1245.         }

  1246. 

  1247.         /* copy green component of alpha image to alpha plane of primary image */

  1248.         for (y = 0; y < s->height; y++) {

  1249.             ap = GET_PIXEL(s->alpha_frame, 0, y) + 2;

  1250.             pp = p->data[3] + p->linesize[3] * y;

  1251.             for (x = 0; x < s->width; x++) {

  1252.                 *pp = *ap;

  1253.                 pp++;

  1254.                 ap += 4;

  1255.             }

  1256.         }

  1257.         av_frame_free(&s->alpha_frame);

  1258.     }

  1259. 

  1260.     /* apply alpha filtering */

  1261.     if (s->alpha_filter)

  1262.         alpha_inverse_prediction(p, s->alpha_filter);

  1263. 

  1264.     return 0;

  1265. }

  1266. 

  1267. static int vp8_lossy_decode_frame(AVCodecContext *avctx, AVFrame *p,

  1268.                                   int *got_frame, uint8_t *data_start,

  1269.                                   unsigned int data_size)

  1270. {

  1271.     WebPContext *s = avctx->priv_data;

  1272.     AVPacket pkt;

  1273.     int ret;

  1274. 

  1275.     if (!s->initialized) {

  1276.         ff_vp8_decode_init(avctx);

  1277.         s->initialized = 1;

  1278.         if (s->has_alpha)

  1279.             avctx->pix_fmt = AV_PIX_FMT_YUVA420P;

  1280.     }

  1281.     s->lossless = 0;

  1282. 

  1283.     if (data_size > INT_MAX) {

  1284.         av_log(avctx, AV_LOG_ERROR, "unsupported chunk size\n");

  1285.         return AVERROR_PATCHWELCOME;

  1286.     }

  1287. 

  1288.     av_init_packet(&pkt);

  1289.     pkt.data = data_start;

  1290.     pkt.size = data_size;

  1291. 

  1292.     ret = ff_vp8_decode_frame(avctx, p, got_frame, &pkt);

  1293.     if (s->has_alpha) {

  1294.         ret = vp8_lossy_decode_alpha(avctx, p, s->alpha_data,

  1295.                                      s->alpha_data_size);

  1296.         if (ret < 0)

  1297.             return ret;

  1298.     }

  1299.     return ret;

  1300. }

  1301. 

  1302. static int webp_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,

  1303.                              AVPacket *avpkt)

  1304. {

  1305.     AVFrame * const p = data;

  1306.     WebPContext *s = avctx->priv_data;

  1307.     GetByteContext gb;

  1308.     int ret;

  1309.     uint32_t chunk_type, chunk_size;

  1310.     int vp8x_flags = 0;

  1311. 

  1312.     s->avctx     = avctx;

  1313.     s->width     = 0;

  1314.     s->height    = 0;

  1315.     *got_frame   = 0;

  1316.     s->has_alpha = 0;

  1317.     bytestream2_init(&gb, avpkt->data, avpkt->size);

  1318. 

  1319.     if (bytestream2_get_bytes_left(&gb) < 12)

  1320.         return AVERROR_INVALIDDATA;

  1321. 

  1322.     if (bytestream2_get_le32(&gb) != MKTAG('R', 'I', 'F', 'F')) {

  1323.         av_log(avctx, AV_LOG_ERROR, "missing RIFF tag\n");

  1324.         return AVERROR_INVALIDDATA;

  1325.     }

  1326. 

  1327.     chunk_size = bytestream2_get_le32(&gb);

  1328.     if (bytestream2_get_bytes_left(&gb) < chunk_size)

  1329.         return AVERROR_INVALIDDATA;

  1330. 

  1331.     if (bytestream2_get_le32(&gb) != MKTAG('W', 'E', 'B', 'P')) {

  1332.         av_log(avctx, AV_LOG_ERROR, "missing WEBP tag\n");

  1333.         return AVERROR_INVALIDDATA;

  1334.     }

  1335. 

  1336.     while (bytestream2_get_bytes_left(&gb) > 0) {

  1337.         char chunk_str[5] = { 0 };

  1338. 

  1339.         chunk_type = bytestream2_get_le32(&gb);

  1340.         chunk_size = bytestream2_get_le32(&gb);

  1341.         if (chunk_size == UINT32_MAX)

  1342.             return AVERROR_INVALIDDATA;

  1343.         chunk_size += chunk_size & 1;

  1344. 

  1345.         if (bytestream2_get_bytes_left(&gb) < chunk_size)

  1346.             return AVERROR_INVALIDDATA;

  1347. 

  1348.         switch (chunk_type) {

  1349.         case MKTAG('V', 'P', '8', ' '):

  1350.             if (!*got_frame) {

  1351.                 ret = vp8_lossy_decode_frame(avctx, p, got_frame,

  1352.                                              avpkt->data + bytestream2_tell(&gb),

  1353.                                              chunk_size);

  1354.                 if (ret < 0)

  1355.                     return ret;

  1356.             }

  1357.             bytestream2_skip(&gb, chunk_size);

  1358.             break;

  1359.         case MKTAG('V', 'P', '8', 'L'):

  1360.             if (!*got_frame) {

  1361.                 ret = vp8_lossless_decode_frame(avctx, p, got_frame,

  1362.                                                 avpkt->data + bytestream2_tell(&gb),

  1363.                                                 chunk_size, 0);

  1364.                 if (ret < 0)

  1365.                     return ret;

  1366.             }

  1367.             bytestream2_skip(&gb, chunk_size);

  1368.             break;

  1369.         case MKTAG('V', 'P', '8', 'X'):

  1370.             vp8x_flags = bytestream2_get_byte(&gb);

  1371.             bytestream2_skip(&gb, 3);

  1372.             s->width  = bytestream2_get_le24(&gb) + 1;

  1373.             s->height = bytestream2_get_le24(&gb) + 1;

  1374.             ret = av_image_check_size(s->width, s->height, 0, avctx);

  1375.             if (ret < 0)

  1376.                 return ret;

  1377.             break;

  1378.         case MKTAG('A', 'L', 'P', 'H'): {

  1379.             int alpha_header, filter_m, compression;

  1380. 

  1381.             if (!(vp8x_flags & VP8X_FLAG_ALPHA)) {

  1382.                 av_log(avctx, AV_LOG_WARNING,

  1383.                        "ALPHA chunk present, but alpha bit not set in the "

  1384.                        "VP8X header\n");

  1385.             }

  1386.             if (chunk_size == 0) {

  1387.                 av_log(avctx, AV_LOG_ERROR, "invalid ALPHA chunk size\n");

  1388.                 return AVERROR_INVALIDDATA;

  1389.             }

  1390.             alpha_header       = bytestream2_get_byte(&gb);

  1391.             s->alpha_data      = avpkt->data + bytestream2_tell(&gb);

  1392.             s->alpha_data_size = chunk_size - 1;

  1393.             bytestream2_skip(&gb, s->alpha_data_size);

  1394. 

  1395.             filter_m    = (alpha_header >> 2) & 0x03;

  1396.             compression =  alpha_header       & 0x03;

  1397. 

  1398.             if (compression > ALPHA_COMPRESSION_VP8L) {

  1399.                 av_log(avctx, AV_LOG_VERBOSE,

  1400.                        "skipping unsupported ALPHA chunk\n");

  1401.             } else {

  1402.                 s->has_alpha         = 1;

  1403.                 s->alpha_compression = compression;

  1404.                 s->alpha_filter      = filter_m;

  1405.             }

  1406. 

  1407.             break;

  1408.         }

  1409.         case MKTAG('I', 'C', 'C', 'P'):

  1410.         case MKTAG('A', 'N', 'I', 'M'):

  1411.         case MKTAG('A', 'N', 'M', 'F'):

  1412.         case MKTAG('E', 'X', 'I', 'F'):

  1413.         case MKTAG('X', 'M', 'P', ' '):

  1414.             AV_WL32(chunk_str, chunk_type);

  1415.             av_log(avctx, AV_LOG_VERBOSE, "skipping unsupported chunk: %s\n",

  1416.                    chunk_str);

  1417.             bytestream2_skip(&gb, chunk_size);

  1418.             break;

  1419.         default:

  1420.             AV_WL32(chunk_str, chunk_type);

  1421.             av_log(avctx, AV_LOG_VERBOSE, "skipping unknown chunk: %s\n",

  1422.                    chunk_str);

  1423.             bytestream2_skip(&gb, chunk_size);

  1424.             break;

  1425.         }

  1426.     }

  1427. 

  1428.     if (!*got_frame) {

  1429.         av_log(avctx, AV_LOG_ERROR, "image data not found\n");

  1430.         return AVERROR_INVALIDDATA;

  1431.     }

  1432. 

  1433.     return avpkt->size;

  1434. }

  1435. 

  1436. static av_cold int webp_decode_close(AVCodecContext *avctx)

  1437. {

  1438.     WebPContext *s = avctx->priv_data;

  1439. 

  1440.     if (s->initialized)

  1441.         return ff_vp8_decode_free(avctx);

  1442. 

  1443.     return 0;

  1444. }

  1445. 

  1446. AVCodec ff_webp_decoder = {

  1447.     .name           = "webp",

  1448.     .long_name      = NULL_IF_CONFIG_SMALL("WebP image"),

  1449.     .type           = AVMEDIA_TYPE_VIDEO,

  1450.     .id             = AV_CODEC_ID_WEBP,

  1451.     .priv_data_size = sizeof(WebPContext),

  1452.     .decode         = webp_decode_frame,

  1453.     .close          = webp_decode_close,

  1454.     .capabilities   = CODEC_CAP_DR1 | CODEC_CAP_FRAME_THREADS,

  1455. };