// 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 <assert.h>
#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "./backward_references.h"
#include "../webp/format_constants.h"
#include "../webp/types.h"
#ifdef __cplusplus
extern "C" {
#endif
// A simple container for histograms of data.
typedef struct {
// literal_ contains green literal, palette-code and
// copy-length-prefix histogram
int literal_[PIX_OR_COPY_CODES_MAX];
int red_[256];
int blue_[256];
int alpha_[256];
// Backward reference prefix-code histogram.
int distance_[NUM_DISTANCE_CODES];
int palette_code_bits_;
double bit_cost_; // cached value of VP8LHistogramEstimateBits(this)
} VP8LHistogram;
// Collection of histograms with fixed capacity, allocated as one
// big memory chunk. Can be destroyed by simply calling 'free()'.
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);
// 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);
// 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);
// Accumulate a token 'v' into a histogram.
void VP8LHistogramAddSinglePixOrCopy(VP8LHistogram* const histo,
const PixOrCopy* const v);
// Estimate how many bits the combined entropy of literals and distance
// approximately maps to.
double VP8LHistogramEstimateBits(const VP8LHistogram* const p);
// This function estimates the cost in bits excluding the bits needed to
// represent the entropy code itself.
double VP8LHistogramEstimateBitsBulk(const VP8LHistogram* const p);
static WEBP_INLINE int VP8LHistogramNumCodes(const VP8LHistogram* const p) {
return 256 + NUM_LENGTH_CODES +
((p->palette_code_bits_ > 0) ? (1 << p->palette_code_bits_) : 0);
}
// Builds the histogram image.
int VP8LGetHistoImageSymbols(int xsize, int ysize,
const VP8LBackwardRefs* const refs,
int quality, int histogram_bits, int cache_bits,
VP8LHistogramSet* const image_in,
uint16_t* const histogram_symbols);
#ifdef __cplusplus
}
#endif
#endif // WEBP_ENC_HISTOGRAM_H_