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| 1 // Copyright 2012 Google Inc. All Rights Reserved. |
| 2 // |
| 3 // This code is licensed under the same terms as WebM: |
| 4 // Software License Agreement: http://www.webmproject.org/license/software/ |
| 5 // Additional IP Rights Grant: http://www.webmproject.org/license/additional/ |
| 6 // ----------------------------------------------------------------------------- |
| 7 // |
| 8 // Author: Jyrki Alakuijala (jyrki@google.com) |
| 9 // |
| 10 // Models the histograms of literal and distance codes. |
| 11 |
| 12 #ifndef WEBP_ENC_HISTOGRAM_H_ |
| 13 #define WEBP_ENC_HISTOGRAM_H_ |
| 14 |
| 15 #include <assert.h> |
| 16 #include <stddef.h> |
| 17 #include <stdlib.h> |
| 18 #include <stdio.h> |
| 19 #include <string.h> |
| 20 |
| 21 #include "./backward_references.h" |
| 22 #include "../webp/format_constants.h" |
| 23 #include "../webp/types.h" |
| 24 |
| 25 #if defined(__cplusplus) || defined(c_plusplus) |
| 26 extern "C" { |
| 27 #endif |
| 28 |
| 29 // A simple container for histograms of data. |
| 30 typedef struct { |
| 31 // literal_ contains green literal, palette-code and |
| 32 // copy-length-prefix histogram |
| 33 int literal_[PIX_OR_COPY_CODES_MAX]; |
| 34 int red_[256]; |
| 35 int blue_[256]; |
| 36 int alpha_[256]; |
| 37 // Backward reference prefix-code histogram. |
| 38 int distance_[NUM_DISTANCE_CODES]; |
| 39 int palette_code_bits_; |
| 40 double bit_cost_; // cached value of VP8LHistogramEstimateBits(this) |
| 41 } VP8LHistogram; |
| 42 |
| 43 // Collection of histograms with fixed capacity, allocated as one |
| 44 // big memory chunk. Can be destroyed by simply calling 'free()'. |
| 45 typedef struct { |
| 46 int size; // number of slots currently in use |
| 47 int max_size; // maximum capacity |
| 48 VP8LHistogram** histograms; |
| 49 } VP8LHistogramSet; |
| 50 |
| 51 // Create the histogram. |
| 52 // |
| 53 // The input data is the PixOrCopy data, which models the literals, stop |
| 54 // codes and backward references (both distances and lengths). Also: if |
| 55 // palette_code_bits is >= 0, initialize the histogram with this value. |
| 56 void VP8LHistogramCreate(VP8LHistogram* const p, |
| 57 const VP8LBackwardRefs* const refs, |
| 58 int palette_code_bits); |
| 59 |
| 60 // Set the palette_code_bits and reset the stats. |
| 61 void VP8LHistogramInit(VP8LHistogram* const p, int palette_code_bits); |
| 62 |
| 63 // Collect all the references into a histogram (without reset) |
| 64 void VP8LHistogramStoreRefs(const VP8LBackwardRefs* const refs, |
| 65 VP8LHistogram* const histo); |
| 66 |
| 67 // Allocate an array of pointer to histograms, allocated and initialized |
| 68 // using 'cache_bits'. Return NULL in case of memory error. |
| 69 VP8LHistogramSet* VP8LAllocateHistogramSet(int size, int cache_bits); |
| 70 |
| 71 // Accumulate a token 'v' into a histogram. |
| 72 void VP8LHistogramAddSinglePixOrCopy(VP8LHistogram* const histo, |
| 73 const PixOrCopy* const v); |
| 74 |
| 75 // Estimate how many bits the combined entropy of literals and distance |
| 76 // approximately maps to. |
| 77 double VP8LHistogramEstimateBits(const VP8LHistogram* const p); |
| 78 |
| 79 // This function estimates the cost in bits excluding the bits needed to |
| 80 // represent the entropy code itself. |
| 81 double VP8LHistogramEstimateBitsBulk(const VP8LHistogram* const p); |
| 82 |
| 83 static WEBP_INLINE void VP8LHistogramAdd(VP8LHistogram* const p, |
| 84 const VP8LHistogram* const a) { |
| 85 int i; |
| 86 for (i = 0; i < PIX_OR_COPY_CODES_MAX; ++i) { |
| 87 p->literal_[i] += a->literal_[i]; |
| 88 } |
| 89 for (i = 0; i < NUM_DISTANCE_CODES; ++i) { |
| 90 p->distance_[i] += a->distance_[i]; |
| 91 } |
| 92 for (i = 0; i < 256; ++i) { |
| 93 p->red_[i] += a->red_[i]; |
| 94 p->blue_[i] += a->blue_[i]; |
| 95 p->alpha_[i] += a->alpha_[i]; |
| 96 } |
| 97 } |
| 98 |
| 99 static WEBP_INLINE int VP8LHistogramNumCodes(const VP8LHistogram* const p) { |
| 100 return 256 + NUM_LENGTH_CODES + |
| 101 ((p->palette_code_bits_ > 0) ? (1 << p->palette_code_bits_) : 0); |
| 102 } |
| 103 |
| 104 // Builds the histogram image. |
| 105 int VP8LGetHistoImageSymbols(int xsize, int ysize, |
| 106 const VP8LBackwardRefs* const refs, |
| 107 int quality, int histogram_bits, int cache_bits, |
| 108 VP8LHistogramSet* const image_in, |
| 109 uint16_t* const histogram_symbols); |
| 110 |
| 111 #if defined(__cplusplus) || defined(c_plusplus) |
| 112 } |
| 113 #endif |
| 114 |
| 115 #endif // WEBP_ENC_HISTOGRAM_H_ |
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