1// Copyright 2012 Google Inc. All Rights Reserved. 2// 3// Use of this source code is governed by a BSD-style license 4// that can be found in the COPYING file in the root of the source 5// tree. An additional intellectual property rights grant can be found 6// in the file PATENTS. All contributing project authors may 7// be found in the AUTHORS file in the root of the source tree. 8// ----------------------------------------------------------------------------- 9// 10// Author: Jyrki Alakuijala (jyrki@google.com) 11// 12// Models the histograms of literal and distance codes. 13 14#ifndef WEBP_ENC_HISTOGRAM_H_ 15#define WEBP_ENC_HISTOGRAM_H_ 16 17#include <string.h> 18 19#include "./backward_references_enc.h" 20#include "../webp/format_constants.h" 21#include "../webp/types.h" 22 23#ifdef __cplusplus 24extern "C" { 25#endif 26 27// Not a trivial literal symbol. 28#define VP8L_NON_TRIVIAL_SYM (0xffffffff) 29 30// A simple container for histograms of data. 31typedef struct { 32 // literal_ contains green literal, palette-code and 33 // copy-length-prefix histogram 34 uint32_t* literal_; // Pointer to the allocated buffer for literal. 35 uint32_t red_[NUM_LITERAL_CODES]; 36 uint32_t blue_[NUM_LITERAL_CODES]; 37 uint32_t alpha_[NUM_LITERAL_CODES]; 38 // Backward reference prefix-code histogram. 39 uint32_t distance_[NUM_DISTANCE_CODES]; 40 int palette_code_bits_; 41 uint32_t trivial_symbol_; // True, if histograms for Red, Blue & Alpha 42 // literal symbols are single valued. 43 double bit_cost_; // cached value of bit cost. 44 double literal_cost_; // Cached values of dominant entropy costs: 45 double red_cost_; // literal, red & blue. 46 double blue_cost_; 47} VP8LHistogram; 48 49// Collection of histograms with fixed capacity, allocated as one 50// big memory chunk. Can be destroyed by calling WebPSafeFree(). 51typedef struct { 52 int size; // number of slots currently in use 53 int max_size; // maximum capacity 54 VP8LHistogram** histograms; 55} VP8LHistogramSet; 56 57// Create the histogram. 58// 59// The input data is the PixOrCopy data, which models the literals, stop 60// codes and backward references (both distances and lengths). Also: if 61// palette_code_bits is >= 0, initialize the histogram with this value. 62void VP8LHistogramCreate(VP8LHistogram* const p, 63 const VP8LBackwardRefs* const refs, 64 int palette_code_bits); 65 66// Return the size of the histogram for a given palette_code_bits. 67int VP8LGetHistogramSize(int palette_code_bits); 68 69// Set the palette_code_bits and reset the stats. 70void VP8LHistogramInit(VP8LHistogram* const p, int palette_code_bits); 71 72// Collect all the references into a histogram (without reset) 73void VP8LHistogramStoreRefs(const VP8LBackwardRefs* const refs, 74 VP8LHistogram* const histo); 75 76// Free the memory allocated for the histogram. 77void VP8LFreeHistogram(VP8LHistogram* const histo); 78 79// Free the memory allocated for the histogram set. 80void VP8LFreeHistogramSet(VP8LHistogramSet* const histo); 81 82// Allocate an array of pointer to histograms, allocated and initialized 83// using 'cache_bits'. Return NULL in case of memory error. 84VP8LHistogramSet* VP8LAllocateHistogramSet(int size, int cache_bits); 85 86// Allocate and initialize histogram object with specified 'cache_bits'. 87// Returns NULL in case of memory error. 88// Special case of VP8LAllocateHistogramSet, with size equals 1. 89VP8LHistogram* VP8LAllocateHistogram(int cache_bits); 90 91// Accumulate a token 'v' into a histogram. 92void VP8LHistogramAddSinglePixOrCopy(VP8LHistogram* const histo, 93 const PixOrCopy* const v); 94 95static WEBP_INLINE int VP8LHistogramNumCodes(int palette_code_bits) { 96 return NUM_LITERAL_CODES + NUM_LENGTH_CODES + 97 ((palette_code_bits > 0) ? (1 << palette_code_bits) : 0); 98} 99 100// Builds the histogram image. 101int VP8LGetHistoImageSymbols(int xsize, int ysize, 102 const VP8LBackwardRefs* const refs, 103 int quality, int low_effort, 104 int histogram_bits, int cache_bits, 105 VP8LHistogramSet* const image_in, 106 VP8LHistogramSet* const tmp_histos, 107 uint16_t* const histogram_symbols); 108 109// Returns the entropy for the symbols in the input array. 110// Also sets trivial_symbol to the code value, if the array has only one code 111// value. Otherwise, set it to VP8L_NON_TRIVIAL_SYM. 112double VP8LBitsEntropy(const uint32_t* const array, int n, 113 uint32_t* const trivial_symbol); 114 115// Estimate how many bits the combined entropy of literals and distance 116// approximately maps to. 117double VP8LHistogramEstimateBits(const VP8LHistogram* const p); 118 119#ifdef __cplusplus 120} 121#endif 122 123#endif // WEBP_ENC_HISTOGRAM_H_ 124