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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)
//
// Models the histograms of literal and distance codes.
#ifndef WEBP_ENC_HISTOGRAM_H_
#define WEBP_ENC_HISTOGRAM_H_
#include <string.h>
#include "./backward_references.h"
#include "../webp/format_constants.h"
#include "../webp/types.h"
#ifdef __cplusplus
extern "C" {
#endif
// Not a trivial literal symbol.
#define VP8L_NON_TRIVIAL_SYM (0xffffffff)
// A simple container for histograms of data.
typedef struct {
// literal_ contains green literal, palette-code and
// copy-length-prefix histogram
uint32_t* literal_; // Pointer to the allocated buffer for literal.
uint32_t red_[NUM_LITERAL_CODES];
uint32_t blue_[NUM_LITERAL_CODES];
uint32_t alpha_[NUM_LITERAL_CODES];
// Backward reference prefix-code histogram.
uint32_t distance_[NUM_DISTANCE_CODES];
int palette_code_bits_;
uint32_t trivial_symbol_; // True, if histograms for Red, Blue & Alpha
// literal symbols are single valued.
double bit_cost_; // cached value of bit cost.
double literal_cost_; // Cached values of dominant entropy costs:
double red_cost_; // literal, red & blue.
double blue_cost_;
} VP8LHistogram;
// Collection of histograms with fixed capacity, allocated as one
// big memory chunk. Can be destroyed by calling WebPSafeFree().
typedef struct {
int size; // number of slots currently in use
int max_size; // maximum capacity
VP8LHistogram** histograms;
} VP8LHistogramSet;
// Create the histogram.
//
// The input data is the PixOrCopy data, which models the literals, stop
// codes and backward references (both distances and lengths). Also: if
// palette_code_bits is >= 0, initialize the histogram with this value.
void VP8LHistogramCreate(VP8LHistogram* const p,
const VP8LBackwardRefs* const refs,
int palette_code_bits);
// Return the size of the histogram for a given palette_code_bits.
int VP8LGetHistogramSize(int palette_code_bits);
// Set the palette_code_bits and reset the stats.
void VP8LHistogramInit(VP8LHistogram* const p, int palette_code_bits);
// Collect all the references into a histogram (without reset)
void VP8LHistogramStoreRefs(const VP8LBackwardRefs* const refs,
VP8LHistogram* const histo);
// Free the memory allocated for the histogram.
void VP8LFreeHistogram(VP8LHistogram* const histo);
// Free the memory allocated for the histogram set.
void VP8LFreeHistogramSet(VP8LHistogramSet* const histo);
// Allocate an array of pointer to histograms, allocated and initialized
// using 'cache_bits'. Return NULL in case of memory error.
VP8LHistogramSet* VP8LAllocateHistogramSet(int size, int cache_bits);
// Allocate and initialize histogram object with specified 'cache_bits'.
// Returns NULL in case of memory error.
// Special case of VP8LAllocateHistogramSet, with size equals 1.
VP8LHistogram* VP8LAllocateHistogram(int cache_bits);
// Accumulate a token 'v' into a histogram.
void VP8LHistogramAddSinglePixOrCopy(VP8LHistogram* const histo,
const PixOrCopy* const v);
static WEBP_INLINE int VP8LHistogramNumCodes(int palette_code_bits) {
return NUM_LITERAL_CODES + NUM_LENGTH_CODES +
((palette_code_bits > 0) ? (1 << palette_code_bits) : 0);
}
// Builds the histogram image.
int VP8LGetHistoImageSymbols(int xsize, int ysize,
const VP8LBackwardRefs* const refs,
int quality, int low_effort,
int histogram_bits, int cache_bits,
VP8LHistogramSet* const image_in,
VP8LHistogramSet* const tmp_histos,
uint16_t* const histogram_symbols);
// Returns the entropy for the symbols in the input array.
// Also sets trivial_symbol to the code value, if the array has only one code
// value. Otherwise, set it to VP8L_NON_TRIVIAL_SYM.
double VP8LBitsEntropy(const uint32_t* const array, int n,
uint32_t* const trivial_symbol);
// Estimate how many bits the combined entropy of literals and distance
// approximately maps to.
double VP8LHistogramEstimateBits(const VP8LHistogram* const p);
#ifdef __cplusplus
}
#endif
#endif // WEBP_ENC_HISTOGRAM_H_
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