libwebp-0.6.0-rc1

third_party/libwebp/enc/backward_references.h

-// 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.
-// -----------------------------------------------------------------------------
-//
-// Author: Jyrki Alakuijala (jyrki@google.com)
-//
-
-#ifndef WEBP_ENC_BACKWARD_REFERENCES_H_
-#define WEBP_ENC_BACKWARD_REFERENCES_H_
-
-#include <assert.h>
-#include <stdlib.h>
-#include "../webp/types.h"
-#include "../webp/format_constants.h"
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-// The maximum allowed limit is 11.
-#define MAX_COLOR_CACHE_BITS 10
-
-// -----------------------------------------------------------------------------
-// PixOrCopy
-
-enum Mode {
-  kLiteral,
-  kCacheIdx,
-  kCopy,
-  kNone
-};
-
-typedef struct {
-  // mode as uint8_t to make the memory layout to be exactly 8 bytes.
-  uint8_t mode;
-  uint16_t len;
-  uint32_t argb_or_distance;
-} PixOrCopy;
-
-static WEBP_INLINE PixOrCopy PixOrCopyCreateCopy(uint32_t distance,
-                                                 uint16_t len) {
-  PixOrCopy retval;
-  retval.mode = kCopy;
-  retval.argb_or_distance = distance;
-  retval.len = len;
-  return retval;
-}
-
-static WEBP_INLINE PixOrCopy PixOrCopyCreateCacheIdx(int idx) {
-  PixOrCopy retval;
-  assert(idx >= 0);
-  assert(idx < (1 << MAX_COLOR_CACHE_BITS));
-  retval.mode = kCacheIdx;
-  retval.argb_or_distance = idx;
-  retval.len = 1;
-  return retval;
-}
-
-static WEBP_INLINE PixOrCopy PixOrCopyCreateLiteral(uint32_t argb) {
-  PixOrCopy retval;
-  retval.mode = kLiteral;
-  retval.argb_or_distance = argb;
-  retval.len = 1;
-  return retval;
-}
-
-static WEBP_INLINE int PixOrCopyIsLiteral(const PixOrCopy* const p) {
-  return (p->mode == kLiteral);
-}
-
-static WEBP_INLINE int PixOrCopyIsCacheIdx(const PixOrCopy* const p) {
-  return (p->mode == kCacheIdx);
-}
-
-static WEBP_INLINE int PixOrCopyIsCopy(const PixOrCopy* const p) {
-  return (p->mode == kCopy);
-}
-
-static WEBP_INLINE uint32_t PixOrCopyLiteral(const PixOrCopy* const p,
-                                             int component) {
-  assert(p->mode == kLiteral);
-  return (p->argb_or_distance >> (component * 8)) & 0xff;
-}
-
-static WEBP_INLINE uint32_t PixOrCopyLength(const PixOrCopy* const p) {
-  return p->len;
-}
-
-static WEBP_INLINE uint32_t PixOrCopyArgb(const PixOrCopy* const p) {
-  assert(p->mode == kLiteral);
-  return p->argb_or_distance;
-}
-
-static WEBP_INLINE uint32_t PixOrCopyCacheIdx(const PixOrCopy* const p) {
-  assert(p->mode == kCacheIdx);
-  assert(p->argb_or_distance < (1U << MAX_COLOR_CACHE_BITS));
-  return p->argb_or_distance;
-}
-
-static WEBP_INLINE uint32_t PixOrCopyDistance(const PixOrCopy* const p) {
-  assert(p->mode == kCopy);
-  return p->argb_or_distance;
-}
-
-// -----------------------------------------------------------------------------
-// VP8LHashChain
-
-#define HASH_BITS 18
-#define HASH_SIZE (1 << HASH_BITS)
-
-typedef struct VP8LHashChain VP8LHashChain;
-struct VP8LHashChain {
-  // The 20 most significant bits contain the offset at which the best match
-  // is found. These 20 bits are the limit defined by GetWindowSizeForHashChain
-  // (through WINDOW_SIZE = 1<<20).
-  // The lower 12 bits contain the length of the match. The 12 bit limit is
-  // defined in MaxFindCopyLength with MAX_LENGTH=4096.
-  uint32_t* offset_length_;
-  // This is the maximum size of the hash_chain that can be constructed.
-  // Typically this is the pixel count (width x height) for a given image.
-  int size_;
-};
-
-// Must be called first, to set size.
-int VP8LHashChainInit(VP8LHashChain* const p, int size);
-// Pre-compute the best matches for argb.
-int VP8LHashChainFill(VP8LHashChain* const p, int quality,
-                      const uint32_t* const argb, int xsize, int ysize);
-void VP8LHashChainClear(VP8LHashChain* const p);  // release memory
-
-// -----------------------------------------------------------------------------
-// VP8LBackwardRefs (block-based backward-references storage)
-
-// maximum number of reference blocks the image will be segmented into
-#define MAX_REFS_BLOCK_PER_IMAGE 16
-
-typedef struct PixOrCopyBlock PixOrCopyBlock;   // forward declaration
-typedef struct VP8LBackwardRefs VP8LBackwardRefs;
-
-// Container for blocks chain
-struct VP8LBackwardRefs {
-  int block_size_;               // common block-size
-  int error_;                    // set to true if some memory error occurred
-  PixOrCopyBlock* refs_;         // list of currently used blocks
-  PixOrCopyBlock** tail_;        // for list recycling
-  PixOrCopyBlock* free_blocks_;  // free-list
-  PixOrCopyBlock* last_block_;   // used for adding new refs (internal)
-};
-
-// Initialize the object. 'block_size' is the common block size to store
-// references (typically, width * height / MAX_REFS_BLOCK_PER_IMAGE).
-void VP8LBackwardRefsInit(VP8LBackwardRefs* const refs, int block_size);
-// Release memory for backward references.
-void VP8LBackwardRefsClear(VP8LBackwardRefs* const refs);
-// Copies the 'src' backward refs to the 'dst'. Returns 0 in case of error.
-int VP8LBackwardRefsCopy(const VP8LBackwardRefs* const src,
-                         VP8LBackwardRefs* const dst);
-
-// Cursor for iterating on references content
-typedef struct {
-  // public:
-  PixOrCopy* cur_pos;           // current position
-  // private:
-  PixOrCopyBlock* cur_block_;   // current block in the refs list
-  const PixOrCopy* last_pos_;   // sentinel for switching to next block
-} VP8LRefsCursor;
-
-// Returns a cursor positioned at the beginning of the references list.
-VP8LRefsCursor VP8LRefsCursorInit(const VP8LBackwardRefs* const refs);
-// Returns true if cursor is pointing at a valid position.
-static WEBP_INLINE int VP8LRefsCursorOk(const VP8LRefsCursor* const c) {
-  return (c->cur_pos != NULL);
-}
-// Move to next block of references. Internal, not to be called directly.
-void VP8LRefsCursorNextBlock(VP8LRefsCursor* const c);
-// Move to next position, or NULL. Should not be called if !VP8LRefsCursorOk().
-static WEBP_INLINE void VP8LRefsCursorNext(VP8LRefsCursor* const c) {
-  assert(c != NULL);
-  assert(VP8LRefsCursorOk(c));
-  if (++c->cur_pos == c->last_pos_) VP8LRefsCursorNextBlock(c);
-}
-
-// -----------------------------------------------------------------------------
-// Main entry points
-
-// Evaluates best possible backward references for specified quality.
-// The input cache_bits to 'VP8LGetBackwardReferences' sets the maximum cache
-// bits to use (passing 0 implies disabling the local color cache).
-// The optimal cache bits is evaluated and set for the *cache_bits parameter.
-// The return value is the pointer to the best of the two backward refs viz,
-// refs[0] or refs[1].
-VP8LBackwardRefs* VP8LGetBackwardReferences(
-    int width, int height, const uint32_t* const argb, int quality,
-    int low_effort, int* const cache_bits,
-    const VP8LHashChain* const hash_chain, VP8LBackwardRefs refs[2]);
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif  // WEBP_ENC_BACKWARD_REFERENCES_H_