text: // Copyright 2012 Google Inc. All Rights Reserved.
  //
  // Use of this source code is governed by a BSD-style license
  // that can be found in the COPYING file in the root of the source
  // tree. An additional intellectual property rights grant can be found
  // in the file PATENTS. All contributing project authors may
  // be found in the AUTHORS file in the root of the source tree.
  // -----------------------------------------------------------------------------
  //
  //  Internal header for constants related to WebP file format.
  //
  // Author: Urvang (urvang@google.com)
  
  #ifndef WEBP_WEBP_FORMAT_CONSTANTS_H_
  #define WEBP_WEBP_FORMAT_CONSTANTS_H_
  
  // Create fourcc of the chunk from the chunk tag characters.
  #define MKFOURCC(a, b, c, d) ((a) | (b) << 8 | (c) << 16 | (uint32_t)(d) << 24)
  
  // VP8 related constants.
  #define VP8_SIGNATURE 0x9d012a              // Signature in VP8 data.
  #define VP8_MAX_PARTITION0_SIZE (1 << 19)   // max size of mode partition
  #define VP8_MAX_PARTITION_SIZE  (1 << 24)   // max size for token partition
  #define VP8_FRAME_HEADER_SIZE 10  // Size of the frame header within VP8 data.
  
  // VP8L related constants.
  #define VP8L_SIGNATURE_SIZE          1      // VP8L signature size.
  #define VP8L_MAGIC_BYTE              0x2f   // VP8L signature byte.
  #define VP8L_IMAGE_SIZE_BITS         14     // Number of bits used to store
                                              // width and height.
  #define VP8L_VERSION_BITS            3      // 3 bits reserved for version.
  #define VP8L_VERSION                 0      // version 0
  #define VP8L_FRAME_HEADER_SIZE       5      // Size of the VP8L frame header.
  
  #define MAX_PALETTE_SIZE             256
  #define MAX_CACHE_BITS               11
  #define HUFFMAN_CODES_PER_META_CODE  5
  #define ARGB_BLACK                   0xff000000
  
  #define DEFAULT_CODE_LENGTH          8
  #define MAX_ALLOWED_CODE_LENGTH      15
  
  #define NUM_LITERAL_CODES            256
  #define NUM_LENGTH_CODES             24
  #define NUM_DISTANCE_CODES           40
  #define CODE_LENGTH_CODES            19
  
  #define MIN_HUFFMAN_BITS             2  // min number of Huffman bits
  #define MAX_HUFFMAN_BITS             9  // max number of Huffman bits
  
  #define TRANSFORM_PRESENT            1  // The bit to be written when next data
                                          // to be read is a transform.
  #define NUM_TRANSFORMS               4  // Maximum number of allowed transform
                                          // in a bitstream.
  typedef enum {
    PREDICTOR_TRANSFORM      = 0,
    CROSS_COLOR_TRANSFORM    = 1,
    SUBTRACT_GREEN           = 2,
    COLOR_INDEXING_TRANSFORM = 3
  } VP8LImageTransformType;
  
  // Alpha related constants.
  #define ALPHA_HEADER_LEN            1
  #define ALPHA_NO_COMPRESSION        0
  #define ALPHA_LOSSLESS_COMPRESSION  1
  #define ALPHA_PREPROCESSED_LEVELS   1
  
  // Mux related constants.
  #define TAG_SIZE           4     // Size of a chunk tag (e.g. "VP8L").
  #define CHUNK_SIZE_BYTES   4     // Size needed to store chunk's size.
  #define CHUNK_HEADER_SIZE  8     // Size of a chunk header.
  #define RIFF_HEADER_SIZE   12    // Size of the RIFF header ("RIFFnnnnWEBP").
  #define ANMF_CHUNK_SIZE    16    // Size of an ANMF chunk.
  #define ANIM_CHUNK_SIZE    6     // Size of an ANIM chunk.
  #define VP8X_CHUNK_SIZE    10    // Size of a VP8X chunk.
  
  #define MAX_CANVAS_SIZE     (1 << 24)     // 24-bit max for VP8X width/height.
  #define MAX_IMAGE_AREA      (1ULL << 32)  // 32-bit max for width x height.
  #define MAX_LOOP_COUNT      (1 << 16)     // maximum value for loop-count
  #define MAX_DURATION        (1 << 24)     // maximum duration
  #define MAX_POSITION_OFFSET (1 << 24)     // maximum frame x/y offset
  
  // Maximum chunk payload is such that adding the header and padding won't
  // overflow a uint32_t.
  #define MAX_CHUNK_PAYLOAD (~0U - CHUNK_HEADER_SIZE - 1)
  
  #endif  /* WEBP_WEBP_FORMAT_CONSTANTS_H_ */
  