third_party/libwebp/enc/histogram.h

   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 <assert.h>
  18 #include <stddef.h>
  19 #include <stdlib.h>
  20 #include <stdio.h>
  21 #include <string.h>
  22
  23 #include "./backward_references.h"
  24 #include "../webp/format_constants.h"
  25 #include "../webp/types.h"
  26
  27 #ifdef __cplusplus
  28 extern "C" {
  29 #endif
  30
  31 // A simple container for histograms of data.
  32 typedef struct {
  33   // literal_ contains green literal, palette-code and
  34   // copy-length-prefix histogram
  35   uint32_t* literal_;         // Pointer to the allocated buffer for literal.
  36   uint32_t red_[NUM_LITERAL_CODES];
  37   uint32_t blue_[NUM_LITERAL_CODES];
  38   uint32_t alpha_[NUM_LITERAL_CODES];
  39   // Backward reference prefix-code histogram.
  40   uint32_t distance_[NUM_DISTANCE_CODES];
  41   int palette_code_bits_;
  42   double bit_cost_;      // cached value of VP8LHistogramEstimateBits(this)
  43   double literal_cost_;  // Cached values of dominant entropy costs:
  44   double red_cost_;      //   literal, red & blue.
  45   double blue_cost_;
  46 } VP8LHistogram;
  47
  48 // Collection of histograms with fixed capacity, allocated as one
  49 // big memory chunk. Can be destroyed by calling WebPSafeFree().
  50 typedef struct {
  51   int size;         // number of slots currently in use
  52   int max_size;     // maximum capacity
  53   VP8LHistogram** histograms;
  54 } VP8LHistogramSet;
  55
  56 // Create the histogram.
  57 //
  58 // The input data is the PixOrCopy data, which models the literals, stop
  59 // codes and backward references (both distances and lengths).  Also: if
  60 // palette_code_bits is >= 0, initialize the histogram with this value.
  61 void VP8LHistogramCreate(VP8LHistogram* const p,
  62                          const VP8LBackwardRefs* const refs,
  63                          int palette_code_bits);
  64
  65 // Return the size of the histogram for a given palette_code_bits.
  66 int VP8LGetHistogramSize(int palette_code_bits);
  67
  68 // Set the palette_code_bits and reset the stats.
  69 void VP8LHistogramInit(VP8LHistogram* const p, int palette_code_bits);
  70
  71 // Collect all the references into a histogram (without reset)
  72 void VP8LHistogramStoreRefs(const VP8LBackwardRefs* const refs,
  73                             VP8LHistogram* const histo);
  74
  75 // Free the memory allocated for the histogram.
  76 void VP8LFreeHistogram(VP8LHistogram* const histo);
  77
  78 // Free the memory allocated for the histogram set.
  79 void VP8LFreeHistogramSet(VP8LHistogramSet* const histo);
  80
  81 // Allocate an array of pointer to histograms, allocated and initialized
  82 // using 'cache_bits'. Return NULL in case of memory error.
  83 VP8LHistogramSet* VP8LAllocateHistogramSet(int size, int cache_bits);
  84
  85 // Allocate and initialize histogram object with specified 'cache_bits'.
  86 // Returns NULL in case of memory error.
  87 // Special case of VP8LAllocateHistogramSet, with size equals 1.
  88 VP8LHistogram* VP8LAllocateHistogram(int cache_bits);
  89
  90 // Accumulate a token 'v' into a histogram.
  91 void VP8LHistogramAddSinglePixOrCopy(VP8LHistogram* const histo,
  92                                      const PixOrCopy* const v);
  93
  94 // Estimate how many bits the combined entropy of literals and distance
  95 // approximately maps to.
  96 double VP8LHistogramEstimateBits(const VP8LHistogram* const p);
  97
  98 // This function estimates the cost in bits excluding the bits needed to
  99 // represent the entropy code itself.
 100 double VP8LHistogramEstimateBitsBulk(const VP8LHistogram* const p);
 101
 102 static WEBP_INLINE int VP8LHistogramNumCodes(int palette_code_bits) {
 103   return NUM_LITERAL_CODES + NUM_LENGTH_CODES +
 104       ((palette_code_bits > 0) ? (1 << palette_code_bits) : 0);
 105 }
 106
 107 // Builds the histogram image.
 108 int VP8LGetHistoImageSymbols(int xsize, int ysize,
 109                              const VP8LBackwardRefs* const refs,
 110                              int quality, int histogram_bits, int cache_bits,
 111                              VP8LHistogramSet* const image_in,
 112                              uint16_t* const histogram_symbols);
 113
 114 #ifdef __cplusplus
 115 }
 116 #endif
 117
 118 #endif  // WEBP_ENC_HISTOGRAM_H_