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101 lines
3.6 KiB
101 lines
3.6 KiB
// Copyright 2012 Google Inc. All Rights Reserved. |
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// |
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// Use of this source code is governed by a BSD-style license |
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// that can be found in the COPYING file in the root of the source |
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// tree. An additional intellectual property rights grant can be found |
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// in the file PATENTS. All contributing project authors may |
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// be found in the AUTHORS file in the root of the source tree. |
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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 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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