116 lines
4.0 KiB
C
116 lines
4.0 KiB
C
// Copyright 2012 Google Inc. All Rights Reserved.
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//
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// This code is licensed under the same terms as WebM:
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// Software License Agreement: http://www.webmproject.org/license/software/
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// Additional IP Rights Grant: http://www.webmproject.org/license/additional/
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// -----------------------------------------------------------------------------
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//
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// Author: Jyrki Alakuijala (jyrki@google.com)
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//
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// Models the histograms of literal and distance codes.
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#ifndef WEBP_ENC_HISTOGRAM_H_
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#define WEBP_ENC_HISTOGRAM_H_
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#include <assert.h>
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#include <stddef.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include "./backward_references.h"
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#include "../webp/format_constants.h"
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#include "../webp/types.h"
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#if defined(__cplusplus) || defined(c_plusplus)
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extern "C" {
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#endif
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// A simple container for histograms of data.
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typedef struct {
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// literal_ contains green literal, palette-code and
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// copy-length-prefix histogram
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int literal_[PIX_OR_COPY_CODES_MAX];
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int red_[256];
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int blue_[256];
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int alpha_[256];
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// Backward reference prefix-code histogram.
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int distance_[NUM_DISTANCE_CODES];
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int palette_code_bits_;
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double bit_cost_; // cached value of VP8LHistogramEstimateBits(this)
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} VP8LHistogram;
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// Collection of histograms with fixed capacity, allocated as one
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// big memory chunk. Can be destroyed by simply calling 'free()'.
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typedef struct {
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int size; // number of slots currently in use
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int max_size; // maximum capacity
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VP8LHistogram** histograms;
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} VP8LHistogramSet;
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// Create the histogram.
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//
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// The input data is the PixOrCopy data, which models the literals, stop
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// codes and backward references (both distances and lengths). Also: if
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// palette_code_bits is >= 0, initialize the histogram with this value.
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void VP8LHistogramCreate(VP8LHistogram* const p,
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const VP8LBackwardRefs* const refs,
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int palette_code_bits);
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// Set the palette_code_bits and reset the stats.
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void VP8LHistogramInit(VP8LHistogram* const p, int palette_code_bits);
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// Collect all the references into a histogram (without reset)
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void VP8LHistogramStoreRefs(const VP8LBackwardRefs* const refs,
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VP8LHistogram* const histo);
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// Allocate an array of pointer to histograms, allocated and initialized
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// using 'cache_bits'. Return NULL in case of memory error.
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VP8LHistogramSet* VP8LAllocateHistogramSet(int size, int cache_bits);
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// Accumulate a token 'v' into a histogram.
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void VP8LHistogramAddSinglePixOrCopy(VP8LHistogram* const histo,
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const PixOrCopy* const v);
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// Estimate how many bits the combined entropy of literals and distance
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// approximately maps to.
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double VP8LHistogramEstimateBits(const VP8LHistogram* const p);
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// This function estimates the cost in bits excluding the bits needed to
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// represent the entropy code itself.
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double VP8LHistogramEstimateBitsBulk(const VP8LHistogram* const p);
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static WEBP_INLINE void VP8LHistogramAdd(VP8LHistogram* const p,
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const VP8LHistogram* const a) {
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int i;
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for (i = 0; i < PIX_OR_COPY_CODES_MAX; ++i) {
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p->literal_[i] += a->literal_[i];
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}
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for (i = 0; i < NUM_DISTANCE_CODES; ++i) {
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p->distance_[i] += a->distance_[i];
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}
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for (i = 0; i < 256; ++i) {
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p->red_[i] += a->red_[i];
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p->blue_[i] += a->blue_[i];
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p->alpha_[i] += a->alpha_[i];
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}
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}
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static WEBP_INLINE int VP8LHistogramNumCodes(const VP8LHistogram* const p) {
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return 256 + NUM_LENGTH_CODES +
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((p->palette_code_bits_ > 0) ? (1 << p->palette_code_bits_) : 0);
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}
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// Builds the histogram image.
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int VP8LGetHistoImageSymbols(int xsize, int ysize,
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const VP8LBackwardRefs* const refs,
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int quality, int histogram_bits, int cache_bits,
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VP8LHistogramSet* const image_in,
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uint16_t* const histogram_symbols);
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#if defined(__cplusplus) || defined(c_plusplus)
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}
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#endif
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#endif // WEBP_ENC_HISTOGRAM_H_
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