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// 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 spec allows 11, we use 9 bits to reduce memory consumption in encoding.
// Having 9 instead of 11 only removes about 0.25 % of compression density.
#define MAX_COLOR_CACHE_BITS 9
// Max ever number of codes we'll use:
#define PIX_OR_COPY_CODES_MAX \
(NUM_LITERAL_CODES + NUM_LENGTH_CODES + (1 << MAX_COLOR_CACHE_BITS))
// -----------------------------------------------------------------------------
// 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;
}
// -----------------------------------------------------------------------------
// VP8LBackwardRefs
typedef struct {
PixOrCopy* refs;
int size; // currently used
int max_size; // maximum capacity
} VP8LBackwardRefs;
// Initialize the object. Must be called first. 'refs' can be NULL.
void VP8LInitBackwardRefs(VP8LBackwardRefs* const refs);
// Release memory and re-initialize the object. 'refs' can be NULL.
void VP8LClearBackwardRefs(VP8LBackwardRefs* const refs);
// Allocate 'max_size' references. Returns false in case of memory error.
int VP8LBackwardRefsAlloc(VP8LBackwardRefs* const refs, int max_size);
// -----------------------------------------------------------------------------
// Main entry points
// Evaluates best possible backward references for specified quality.
// Further optimize for 2D locality if use_2d_locality flag is set.
int VP8LGetBackwardReferences(int width, int height,
const uint32_t* const argb,
int quality, int cache_bits, int use_2d_locality,
VP8LBackwardRefs* const best);
// Produce an estimate for a good color cache size for the image.
int VP8LCalculateEstimateForCacheSize(const uint32_t* const argb,
int xsize, int ysize,
int* const best_cache_bits);
#ifdef __cplusplus
}
#endif
#endif // WEBP_ENC_BACKWARD_REFERENCES_H_
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