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