55414bc573
Note that there are two Godot-specific changes made to libwebp
for the javascript/HTML5 platform. They are documented in the
README.md.
(cherry picked from commit ee3cf211c6)
123 lines
4.7 KiB
C++
123 lines
4.7 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 <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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// Not a trivial literal symbol.
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#define VP8L_NON_TRIVIAL_SYM (0xffffffff)
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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 low_effort,
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int histogram_bits, int cache_bits,
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VP8LHistogramSet* const image_in,
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VP8LHistogramSet* const tmp_histos,
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uint16_t* const histogram_symbols);
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// Returns the entropy for the symbols in the input array.
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// Also sets trivial_symbol to the code value, if the array has only one code
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// value. Otherwise, set it to VP8L_NON_TRIVIAL_SYM.
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double VP8LBitsEntropy(const uint32_t* const array, int n,
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uint32_t* const trivial_symbol);
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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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#ifdef __cplusplus
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}
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#endif
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#endif // WEBP_ENC_HISTOGRAM_H_
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