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 // Author: Jyrki Alakuijala (jyrki (at) google.com) 11 // 12 13 #ifndef WEBP_ENC_BACKWARD_REFERENCES_H_ 14 #define WEBP_ENC_BACKWARD_REFERENCES_H_ 15 16 #include <assert.h> 17 #include <stdlib.h> 18 #include "webp/types.h" 19 #include "webp/format_constants.h" 20 21 #ifdef __cplusplus 22 extern "C" { 23 #endif 24 25 // The spec allows 11, we use 9 bits to reduce memory consumption in encoding. 26 // Having 9 instead of 11 only removes about 0.25 % of compression density. 27 #define MAX_COLOR_CACHE_BITS 9 28 29 // Max ever number of codes we'll use: 30 #define PIX_OR_COPY_CODES_MAX \ 31 (NUM_LITERAL_CODES + NUM_LENGTH_CODES + (1 << MAX_COLOR_CACHE_BITS)) 32 33 // ----------------------------------------------------------------------------- 34 // PixOrCopy 35 36 enum Mode { 37 kLiteral, 38 kCacheIdx, 39 kCopy, 40 kNone 41 }; 42 43 typedef struct { 44 // mode as uint8_t to make the memory layout to be exactly 8 bytes. 45 uint8_t mode; 46 uint16_t len; 47 uint32_t argb_or_distance; 48 } PixOrCopy; 49 50 static WEBP_INLINE PixOrCopy PixOrCopyCreateCopy(uint32_t distance, 51 uint16_t len) { 52 PixOrCopy retval; 53 retval.mode = kCopy; 54 retval.argb_or_distance = distance; 55 retval.len = len; 56 return retval; 57 } 58 59 static WEBP_INLINE PixOrCopy PixOrCopyCreateCacheIdx(int idx) { 60 PixOrCopy retval; 61 assert(idx >= 0); 62 assert(idx < (1 << MAX_COLOR_CACHE_BITS)); 63 retval.mode = kCacheIdx; 64 retval.argb_or_distance = idx; 65 retval.len = 1; 66 return retval; 67 } 68 69 static WEBP_INLINE PixOrCopy PixOrCopyCreateLiteral(uint32_t argb) { 70 PixOrCopy retval; 71 retval.mode = kLiteral; 72 retval.argb_or_distance = argb; 73 retval.len = 1; 74 return retval; 75 } 76 77 static WEBP_INLINE int PixOrCopyIsLiteral(const PixOrCopy* const p) { 78 return (p->mode == kLiteral); 79 } 80 81 static WEBP_INLINE int PixOrCopyIsCacheIdx(const PixOrCopy* const p) { 82 return (p->mode == kCacheIdx); 83 } 84 85 static WEBP_INLINE int PixOrCopyIsCopy(const PixOrCopy* const p) { 86 return (p->mode == kCopy); 87 } 88 89 static WEBP_INLINE uint32_t PixOrCopyLiteral(const PixOrCopy* const p, 90 int component) { 91 assert(p->mode == kLiteral); 92 return (p->argb_or_distance >> (component * 8)) & 0xff; 93 } 94 95 static WEBP_INLINE uint32_t PixOrCopyLength(const PixOrCopy* const p) { 96 return p->len; 97 } 98 99 static WEBP_INLINE uint32_t PixOrCopyArgb(const PixOrCopy* const p) { 100 assert(p->mode == kLiteral); 101 return p->argb_or_distance; 102 } 103 104 static WEBP_INLINE uint32_t PixOrCopyCacheIdx(const PixOrCopy* const p) { 105 assert(p->mode == kCacheIdx); 106 assert(p->argb_or_distance < (1U << MAX_COLOR_CACHE_BITS)); 107 return p->argb_or_distance; 108 } 109 110 static WEBP_INLINE uint32_t PixOrCopyDistance(const PixOrCopy* const p) { 111 assert(p->mode == kCopy); 112 return p->argb_or_distance; 113 } 114 115 // ----------------------------------------------------------------------------- 116 // VP8LHashChain 117 118 #define HASH_BITS 18 119 #define HASH_SIZE (1 << HASH_BITS) 120 121 typedef struct VP8LHashChain VP8LHashChain; 122 struct VP8LHashChain { 123 // Stores the most recently added position with the given hash value. 124 int32_t hash_to_first_index_[HASH_SIZE]; 125 // chain_[pos] stores the previous position with the same hash value 126 // for every pixel in the image. 127 int32_t* chain_; 128 // This is the maximum size of the hash_chain that can be constructed. 129 // Typically this is the pixel count (width x height) for a given image. 130 int size_; 131 }; 132 133 // Must be called first, to set size. 134 int VP8LHashChainInit(VP8LHashChain* const p, int size); 135 void VP8LHashChainClear(VP8LHashChain* const p); // release memory 136 137 // ----------------------------------------------------------------------------- 138 // VP8LBackwardRefs (block-based backward-references storage) 139 140 // maximum number of reference blocks the image will be segmented into 141 #define MAX_REFS_BLOCK_PER_IMAGE 16 142 143 typedef struct PixOrCopyBlock PixOrCopyBlock; // forward declaration 144 typedef struct VP8LBackwardRefs VP8LBackwardRefs; 145 146 // Container for blocks chain 147 struct VP8LBackwardRefs { 148 int block_size_; // common block-size 149 int error_; // set to true if some memory error occurred 150 PixOrCopyBlock* refs_; // list of currently used blocks 151 PixOrCopyBlock** tail_; // for list recycling 152 PixOrCopyBlock* free_blocks_; // free-list 153 PixOrCopyBlock* last_block_; // used for adding new refs (internal) 154 }; 155 156 // Initialize the object. 'block_size' is the common block size to store 157 // references (typically, width * height / MAX_REFS_BLOCK_PER_IMAGE). 158 void VP8LBackwardRefsInit(VP8LBackwardRefs* const refs, int block_size); 159 // Release memory for backward references. 160 void VP8LBackwardRefsClear(VP8LBackwardRefs* const refs); 161 // Copies the 'src' backward refs to the 'dst'. Returns 0 in case of error. 162 int VP8LBackwardRefsCopy(const VP8LBackwardRefs* const src, 163 VP8LBackwardRefs* const dst); 164 165 // Cursor for iterating on references content 166 typedef struct { 167 // public: 168 PixOrCopy* cur_pos; // current position 169 // private: 170 PixOrCopyBlock* cur_block_; // current block in the refs list 171 const PixOrCopy* last_pos_; // sentinel for switching to next block 172 } VP8LRefsCursor; 173 174 // Returns a cursor positioned at the beginning of the references list. 175 VP8LRefsCursor VP8LRefsCursorInit(const VP8LBackwardRefs* const refs); 176 // Returns true if cursor is pointing at a valid position. 177 static WEBP_INLINE int VP8LRefsCursorOk(const VP8LRefsCursor* const c) { 178 return (c->cur_pos != NULL); 179 } 180 // Move to next block of references. Internal, not to be called directly. 181 void VP8LRefsCursorNextBlock(VP8LRefsCursor* const c); 182 // Move to next position, or NULL. Should not be called if !VP8LRefsCursorOk(). 183 static WEBP_INLINE void VP8LRefsCursorNext(VP8LRefsCursor* const c) { 184 assert(c != NULL); 185 assert(VP8LRefsCursorOk(c)); 186 if (++c->cur_pos == c->last_pos_) VP8LRefsCursorNextBlock(c); 187 } 188 189 // ----------------------------------------------------------------------------- 190 // Main entry points 191 192 // Evaluates best possible backward references for specified quality. 193 // Further optimize for 2D locality if use_2d_locality flag is set. 194 // The return value is the pointer to the best of the two backward refs viz, 195 // refs[0] or refs[1]. 196 VP8LBackwardRefs* VP8LGetBackwardReferences( 197 int width, int height, const uint32_t* const argb, int quality, 198 int cache_bits, int use_2d_locality, VP8LHashChain* const hash_chain, 199 VP8LBackwardRefs refs[2]); 200 201 // Produce an estimate for a good color cache size for the image. 202 int VP8LCalculateEstimateForCacheSize(const uint32_t* const argb, 203 int xsize, int ysize, int quality, 204 VP8LHashChain* const hash_chain, 205 VP8LBackwardRefs* const ref, 206 int* const best_cache_bits); 207 208 #ifdef __cplusplus 209 } 210 #endif 211 212 #endif // WEBP_ENC_BACKWARD_REFERENCES_H_ 213
