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Diffstat (limited to 'media/libwebp/enc/histogram_enc.h')
| -rw-r--r-- | media/libwebp/enc/histogram_enc.h | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/media/libwebp/enc/histogram_enc.h b/media/libwebp/enc/histogram_enc.h new file mode 100644 index 000000000..a9d258a16 --- /dev/null +++ b/media/libwebp/enc/histogram_enc.h @@ -0,0 +1,123 @@ +// Copyright 2012 Google Inc. All Rights Reserved. +// +// Use of this source code is governed by a BSD-style license +// that can be found in the COPYING file in the root of the source +// tree. An additional intellectual property rights grant can be found +// in the file PATENTS. All contributing project authors may +// be found in the AUTHORS file in the root of the source tree. +// ----------------------------------------------------------------------------- +// +// Author: Jyrki Alakuijala (jyrki@google.com) +// +// Models the histograms of literal and distance codes. + +#ifndef WEBP_ENC_HISTOGRAM_H_ +#define WEBP_ENC_HISTOGRAM_H_ + +#include <string.h> + +#include "./backward_references_enc.h" +#include "../webp/format_constants.h" +#include "../webp/types.h" + +#ifdef __cplusplus +extern "C" { +#endif + +// Not a trivial literal symbol. +#define VP8L_NON_TRIVIAL_SYM (0xffffffff) + +// A simple container for histograms of data. +typedef struct { + // literal_ contains green literal, palette-code and + // copy-length-prefix histogram + uint32_t* literal_; // Pointer to the allocated buffer for literal. + uint32_t red_[NUM_LITERAL_CODES]; + uint32_t blue_[NUM_LITERAL_CODES]; + uint32_t alpha_[NUM_LITERAL_CODES]; + // Backward reference prefix-code histogram. + uint32_t distance_[NUM_DISTANCE_CODES]; + int palette_code_bits_; + uint32_t trivial_symbol_; // True, if histograms for Red, Blue & Alpha + // literal symbols are single valued. + double bit_cost_; // cached value of bit cost. + double literal_cost_; // Cached values of dominant entropy costs: + double red_cost_; // literal, red & blue. + double blue_cost_; +} VP8LHistogram; + +// Collection of histograms with fixed capacity, allocated as one +// big memory chunk. Can be destroyed by calling WebPSafeFree(). +typedef struct { + int size; // number of slots currently in use + int max_size; // maximum capacity + VP8LHistogram** histograms; +} VP8LHistogramSet; + +// Create the histogram. +// +// The input data is the PixOrCopy data, which models the literals, stop +// codes and backward references (both distances and lengths). Also: if +// palette_code_bits is >= 0, initialize the histogram with this value. +void VP8LHistogramCreate(VP8LHistogram* const p, + const VP8LBackwardRefs* const refs, + int palette_code_bits); + +// Return the size of the histogram for a given palette_code_bits. +int VP8LGetHistogramSize(int palette_code_bits); + +// Set the palette_code_bits and reset the stats. +void VP8LHistogramInit(VP8LHistogram* const p, int palette_code_bits); + +// Collect all the references into a histogram (without reset) +void VP8LHistogramStoreRefs(const VP8LBackwardRefs* const refs, + VP8LHistogram* const histo); + +// Free the memory allocated for the histogram. +void VP8LFreeHistogram(VP8LHistogram* const histo); + +// Free the memory allocated for the histogram set. +void VP8LFreeHistogramSet(VP8LHistogramSet* const histo); + +// Allocate an array of pointer to histograms, allocated and initialized +// using 'cache_bits'. Return NULL in case of memory error. +VP8LHistogramSet* VP8LAllocateHistogramSet(int size, int cache_bits); + +// Allocate and initialize histogram object with specified 'cache_bits'. +// Returns NULL in case of memory error. +// Special case of VP8LAllocateHistogramSet, with size equals 1. +VP8LHistogram* VP8LAllocateHistogram(int cache_bits); + +// Accumulate a token 'v' into a histogram. +void VP8LHistogramAddSinglePixOrCopy(VP8LHistogram* const histo, + const PixOrCopy* const v); + +static WEBP_INLINE int VP8LHistogramNumCodes(int palette_code_bits) { + return NUM_LITERAL_CODES + NUM_LENGTH_CODES + + ((palette_code_bits > 0) ? (1 << palette_code_bits) : 0); +} + +// Builds the histogram image. +int VP8LGetHistoImageSymbols(int xsize, int ysize, + const VP8LBackwardRefs* const refs, + int quality, int low_effort, + int histogram_bits, int cache_bits, + VP8LHistogramSet* const image_in, + VP8LHistogramSet* const tmp_histos, + uint16_t* const histogram_symbols); + +// Returns the entropy for the symbols in the input array. +// Also sets trivial_symbol to the code value, if the array has only one code +// value. Otherwise, set it to VP8L_NON_TRIVIAL_SYM. +double VP8LBitsEntropy(const uint32_t* const array, int n, + uint32_t* const trivial_symbol); + +// Estimate how many bits the combined entropy of literals and distance +// approximately maps to. +double VP8LHistogramEstimateBits(const VP8LHistogram* const p); + +#ifdef __cplusplus +} +#endif + +#endif // WEBP_ENC_HISTOGRAM_H_ |