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