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      1 // Copyright 2012 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 //  Internal header for constants related to WebP file format.
     11 //
     12 // Author: Urvang (urvang (at) google.com)
     13 
     14 #ifndef WEBP_WEBP_FORMAT_CONSTANTS_H_
     15 #define WEBP_WEBP_FORMAT_CONSTANTS_H_
     16 
     17 // Create fourcc of the chunk from the chunk tag characters.
     18 #define MKFOURCC(a, b, c, d) ((uint32_t)(a) | (b) << 8 | (c) << 16 | (d) << 24)
     19 
     20 // VP8 related constants.
     21 #define VP8_SIGNATURE 0x9d012a              // Signature in VP8 data.
     22 #define VP8_MAX_PARTITION0_SIZE (1 << 19)   // max size of mode partition
     23 #define VP8_MAX_PARTITION_SIZE  (1 << 24)   // max size for token partition
     24 #define VP8_FRAME_HEADER_SIZE 10  // Size of the frame header within VP8 data.
     25 
     26 // VP8L related constants.
     27 #define VP8L_SIGNATURE_SIZE          1      // VP8L signature size.
     28 #define VP8L_MAGIC_BYTE              0x2f   // VP8L signature byte.
     29 #define VP8L_IMAGE_SIZE_BITS         14     // Number of bits used to store
     30                                             // width and height.
     31 #define VP8L_VERSION_BITS            3      // 3 bits reserved for version.
     32 #define VP8L_VERSION                 0      // version 0
     33 #define VP8L_FRAME_HEADER_SIZE       5      // Size of the VP8L frame header.
     34 
     35 #define MAX_PALETTE_SIZE             256
     36 #define MAX_CACHE_BITS               11
     37 #define HUFFMAN_CODES_PER_META_CODE  5
     38 #define ARGB_BLACK                   0xff000000
     39 
     40 #define DEFAULT_CODE_LENGTH          8
     41 #define MAX_ALLOWED_CODE_LENGTH      15
     42 
     43 #define NUM_LITERAL_CODES            256
     44 #define NUM_LENGTH_CODES             24
     45 #define NUM_DISTANCE_CODES           40
     46 #define CODE_LENGTH_CODES            19
     47 
     48 #define MIN_HUFFMAN_BITS             2  // min number of Huffman bits
     49 #define MAX_HUFFMAN_BITS             9  // max number of Huffman bits
     50 
     51 #define TRANSFORM_PRESENT            1  // The bit to be written when next data
     52                                         // to be read is a transform.
     53 #define NUM_TRANSFORMS               4  // Maximum number of allowed transform
     54                                         // in a bitstream.
     55 typedef enum {
     56   PREDICTOR_TRANSFORM      = 0,
     57   CROSS_COLOR_TRANSFORM    = 1,
     58   SUBTRACT_GREEN           = 2,
     59   COLOR_INDEXING_TRANSFORM = 3
     60 } VP8LImageTransformType;
     61 
     62 // Alpha related constants.
     63 #define ALPHA_HEADER_LEN            1
     64 #define ALPHA_NO_COMPRESSION        0
     65 #define ALPHA_LOSSLESS_COMPRESSION  1
     66 #define ALPHA_PREPROCESSED_LEVELS   1
     67 
     68 // Mux related constants.
     69 #define TAG_SIZE           4     // Size of a chunk tag (e.g. "VP8L").
     70 #define CHUNK_SIZE_BYTES   4     // Size needed to store chunk's size.
     71 #define CHUNK_HEADER_SIZE  8     // Size of a chunk header.
     72 #define RIFF_HEADER_SIZE   12    // Size of the RIFF header ("RIFFnnnnWEBP").
     73 #define ANMF_CHUNK_SIZE    16    // Size of an ANMF chunk.
     74 #define ANIM_CHUNK_SIZE    6     // Size of an ANIM chunk.
     75 #define FRGM_CHUNK_SIZE    6     // Size of a FRGM chunk.
     76 #define VP8X_CHUNK_SIZE    10    // Size of a VP8X chunk.
     77 
     78 #define MAX_CANVAS_SIZE     (1 << 24)     // 24-bit max for VP8X width/height.
     79 #define MAX_IMAGE_AREA      (1ULL << 32)  // 32-bit max for width x height.
     80 #define MAX_LOOP_COUNT      (1 << 16)     // maximum value for loop-count
     81 #define MAX_DURATION        (1 << 24)     // maximum duration
     82 #define MAX_POSITION_OFFSET (1 << 24)     // maximum frame/fragment x/y offset
     83 
     84 // Maximum chunk payload is such that adding the header and padding won't
     85 // overflow a uint32_t.
     86 #define MAX_CHUNK_PAYLOAD (~0U - CHUNK_HEADER_SIZE - 1)
     87 
     88 #endif  /* WEBP_WEBP_FORMAT_CONSTANTS_H_ */
     89