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https://github.com/webmproject/libwebp.git
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e0c809ad23
Move all the Entropy evaluation methods to lossless.c (from histogram.c). There's slight difference in the way entropy is computed for evaluating entropy in prediction methods and histogram (literal) for huffman trees. Plan (later) to merge few (static) methods and reduce the code size. This change has no impact on the compression speed/density. Change-Id: Ife3d96a3c4a8d78a91723d9e0a8d1b78c0256a15
113 lines
4.1 KiB
C
113 lines
4.1 KiB
C
// 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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#ifdef __cplusplus
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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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uint32_t* literal_; // Pointer to the allocated buffer for literal.
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uint32_t red_[NUM_LITERAL_CODES];
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uint32_t blue_[NUM_LITERAL_CODES];
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uint32_t alpha_[NUM_LITERAL_CODES];
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// Backward reference prefix-code histogram.
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uint32_t distance_[NUM_DISTANCE_CODES];
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int palette_code_bits_;
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uint32_t trivial_symbol_; // True, if histograms for Red, Blue & Alpha
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// literal symbols are single valued.
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double bit_cost_; // cached value of bit cost.
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double literal_cost_; // Cached values of dominant entropy costs:
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double red_cost_; // literal, red & blue.
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double blue_cost_;
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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 calling WebPSafeFree().
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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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// Return the size of the histogram for a given palette_code_bits.
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int VP8LGetHistogramSize(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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// Free the memory allocated for the histogram.
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void VP8LFreeHistogram(VP8LHistogram* const histo);
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// Free the memory allocated for the histogram set.
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void VP8LFreeHistogramSet(VP8LHistogramSet* 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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// Allocate and initialize histogram object with specified 'cache_bits'.
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// Returns NULL in case of memory error.
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// Special case of VP8LAllocateHistogramSet, with size equals 1.
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VP8LHistogram* VP8LAllocateHistogram(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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static WEBP_INLINE int VP8LHistogramNumCodes(int palette_code_bits) {
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return NUM_LITERAL_CODES + NUM_LENGTH_CODES +
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((palette_code_bits > 0) ? (1 << 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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#ifdef __cplusplus
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}
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#endif
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#endif // WEBP_ENC_HISTOGRAM_H_
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