histogram_enc.h - mozsearch

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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_ENC_H_

#define WEBP_ENC_HISTOGRAM_ENC_H_

#include <string.h>

#include "src/enc/backward_references_enc.h"

#include "src/webp/format_constants.h"

#include "src/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.

  float bit_cost_;           // cached value of bit cost.

  float literal_cost_;       // Cached values of dominant entropy costs:

  float red_cost_;           // literal, red & blue.

  float blue_cost_;

  uint8_t is_used_[5];       // 5 for literal, red, blue, alpha, distance

} 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 cache_bits.

int VP8LGetHistogramSize(int cache_bits);

// Set the palette_code_bits and reset the stats.

// If init_arrays is true, the arrays are also filled with 0's.

void VP8LHistogramInit(VP8LHistogram* const p, int palette_code_bits,

                       int init_arrays);

// 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);

// Set the histograms in set to 0.

void VP8LHistogramSetClear(VP8LHistogramSet* const set);

// 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,

                                     int (*const distance_modifier)(int, int),

                                     int distance_modifier_arg0);

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. pic and percent are for progress.

// Returns false in case of error (stored in pic->error_code).

int VP8LGetHistoImageSymbols(int xsize, int ysize,

                             const VP8LBackwardRefs* const refs, int quality,

                             int low_effort, int histogram_bits, int cache_bits,

                             VP8LHistogramSet* const image_histo,

                             VP8LHistogram* const tmp_histo,

                             uint16_t* const histogram_symbols,

                             const WebPPicture* const pic, int percent_range,

                             int* const percent);

// Returns the entropy for the symbols in the input array.

float VP8LBitsEntropy(const uint32_t* const array, int n);

// Estimate how many bits the combined entropy of literals and distance

// approximately maps to.

float VP8LHistogramEstimateBits(VP8LHistogram* const p);

#ifdef __cplusplus

#endif

#endif  // WEBP_ENC_HISTOGRAM_ENC_H_