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+// Copyright 2012 Google Inc. All Rights Reserved.
+//
+// This code is licensed under the same terms as WebM:
+// Software License Agreement: http://www.webmproject.org/license/software/
+// Additional IP Rights Grant: http://www.webmproject.org/license/additional/
+// -----------------------------------------------------------------------------
+//
+// 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 <assert.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "./backward_references.h"
+#include "../format_constants.h"
+#include "../types.h"
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+// A simple container for histograms of data.
+typedef struct {
+ // literal_ contains green literal, palette-code and
+ // copy-length-prefix histogram
+ int literal_[PIX_OR_COPY_CODES_MAX];
+ int red_[256];
+ int blue_[256];
+ int alpha_[256];
+ // Backward reference prefix-code histogram.
+ int distance_[NUM_DISTANCE_CODES];
+ int palette_code_bits_;
+ double bit_cost_; // cached value of VP8LHistogramEstimateBits(this)
+} VP8LHistogram;
+
+// Collection of histograms with fixed capacity, allocated as one
+// big memory chunk. Can be destroyed by simply calling 'free()'.
+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);
+
+// 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);
+
+// 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);
+
+// Accumulate a token 'v' into a histogram.
+void VP8LHistogramAddSinglePixOrCopy(VP8LHistogram* const histo,
+ const PixOrCopy* const v);
+
+// Estimate how many bits the combined entropy of literals and distance
+// approximately maps to.
+double VP8LHistogramEstimateBits(const VP8LHistogram* const p);
+
+// This function estimates the cost in bits excluding the bits needed to
+// represent the entropy code itself.
+double VP8LHistogramEstimateBitsBulk(const VP8LHistogram* const p);
+
+static WEBP_INLINE void VP8LHistogramAdd(VP8LHistogram* const p,
+ const VP8LHistogram* const a) {
+ int i;
+ for (i = 0; i < PIX_OR_COPY_CODES_MAX; ++i) {
+ p->literal_[i] += a->literal_[i];
+ }
+ for (i = 0; i < NUM_DISTANCE_CODES; ++i) {
+ p->distance_[i] += a->distance_[i];
+ }
+ for (i = 0; i < 256; ++i) {
+ p->red_[i] += a->red_[i];
+ p->blue_[i] += a->blue_[i];
+ p->alpha_[i] += a->alpha_[i];
+ }
+}
+
+static WEBP_INLINE int VP8LHistogramNumCodes(const VP8LHistogram* const p) {
+ return 256 + NUM_LENGTH_CODES +
+ ((p->palette_code_bits_ > 0) ? (1 << p->palette_code_bits_) : 0);
+}
+
+// Builds the histogram image.
+int VP8LGetHistoImageSymbols(int xsize, int ysize,
+ const VP8LBackwardRefs* const refs,
+ int quality, int histogram_bits, int cache_bits,
+ VP8LHistogramSet* const image_in,
+ uint16_t* const histogram_symbols);
+
+#if defined(__cplusplus) || defined(c_plusplus)
+}
+#endif
+
+#endif // WEBP_ENC_HISTOGRAM_H_