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6938111357
libwebp/src/dsp/lossless.h
Lode Vandevenne 6938111357 Improved alpha cleanup for the webp encoder when prediction transform is used. 
Gives 0.9% smaller (2.4% compared to before alpha cleanup) size on the 1000 PNGs dataset:
Alpha cleanup before: 18856614
Alpha cleanup after: 18685802
For reference, with no alpha cleanup: 19159992

Note: WebPCleanupTransparentArea is still also called in WebPEncode. This cleanup still helps
preprocessing in the encoder, and the cases when the prediction transform is not used.

Change-Id: I63e69f48af6ddeb9804e2e603c59dde2718c6c28
2015-12-04 13:50:56 +00:00

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// 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.
// -----------------------------------------------------------------------------
//
// Image transforms and color space conversion methods for lossless decoder.
//
// Authors: Vikas Arora (vikaas.arora@gmail.com)
// Jyrki Alakuijala (jyrki@google.com)
#ifndef WEBP_DSP_LOSSLESS_H_
#define WEBP_DSP_LOSSLESS_H_
#include "../webp/types.h"
#include "../webp/decode.h"
#include "../enc/histogram.h"
#include "../utils/utils.h"
#ifdef __cplusplus
extern "C" {
#endif
#ifdef WEBP_EXPERIMENTAL_FEATURES
#include "../enc/delta_palettization.h"
#endif // WEBP_EXPERIMENTAL_FEATURES
// Not a trivial literal symbol.
#define VP8L_NON_TRIVIAL_SYM (0xffffffff)
//------------------------------------------------------------------------------
// Decoding
typedef uint32_t (*VP8LPredictorFunc)(uint32_t left, const uint32_t* const top);
extern VP8LPredictorFunc VP8LPredictors[16];
typedef void (*VP8LProcessBlueAndRedFunc)(uint32_t* argb_data, int num_pixels);
extern VP8LProcessBlueAndRedFunc VP8LAddGreenToBlueAndRed;
typedef struct {
// Note: the members are uint8_t, so that any negative values are
// automatically converted to "mod 256" values.
uint8_t green_to_red_;
uint8_t green_to_blue_;
uint8_t red_to_blue_;
} VP8LMultipliers;
typedef void (*VP8LTransformColorFunc)(const VP8LMultipliers* const m,
uint32_t* argb_data, int num_pixels);
extern VP8LTransformColorFunc VP8LTransformColorInverse;
struct VP8LTransform; // Defined in dec/vp8li.h.
// Performs inverse transform of data given transform information, start and end
// rows. Transform will be applied to rows [row_start, row_end[.
// The *in and *out pointers refer to source and destination data respectively
// corresponding to the intermediate row (row_start).
void VP8LInverseTransform(const struct VP8LTransform* const transform,
int row_start, int row_end,
const uint32_t* const in, uint32_t* const out);
// Color space conversion.
typedef void (*VP8LConvertFunc)(const uint32_t* src, int num_pixels,
uint8_t* dst);
extern VP8LConvertFunc VP8LConvertBGRAToRGB;
extern VP8LConvertFunc VP8LConvertBGRAToRGBA;
extern VP8LConvertFunc VP8LConvertBGRAToRGBA4444;
extern VP8LConvertFunc VP8LConvertBGRAToRGB565;
extern VP8LConvertFunc VP8LConvertBGRAToBGR;
// Converts from BGRA to other color spaces.
void VP8LConvertFromBGRA(const uint32_t* const in_data, int num_pixels,
WEBP_CSP_MODE out_colorspace, uint8_t* const rgba);
// color mapping related functions.
static WEBP_INLINE uint32_t VP8GetARGBIndex(uint32_t idx) {
return (idx >> 8) & 0xff;
}
static WEBP_INLINE uint8_t VP8GetAlphaIndex(uint8_t idx) {
return idx;
}
static WEBP_INLINE uint32_t VP8GetARGBValue(uint32_t val) {
return val;
}
static WEBP_INLINE uint8_t VP8GetAlphaValue(uint32_t val) {
return (val >> 8) & 0xff;
}
typedef void (*VP8LMapARGBFunc)(const uint32_t* src,
const uint32_t* const color_map,
uint32_t* dst, int y_start,
int y_end, int width);
typedef void (*VP8LMapAlphaFunc)(const uint8_t* src,
const uint32_t* const color_map,
uint8_t* dst, int y_start,
int y_end, int width);
extern VP8LMapARGBFunc VP8LMapColor32b;
extern VP8LMapAlphaFunc VP8LMapColor8b;
// Similar to the static method ColorIndexInverseTransform() that is part of
// lossless.c, but used only for alpha decoding. It takes uint8_t (rather than
// uint32_t) arguments for 'src' and 'dst'.
void VP8LColorIndexInverseTransformAlpha(
const struct VP8LTransform* const transform, int y_start, int y_end,
const uint8_t* src, uint8_t* dst);
// Expose some C-only fallback functions
void VP8LTransformColorInverse_C(const VP8LMultipliers* const m,
uint32_t* data, int num_pixels);
void VP8LConvertBGRAToRGB_C(const uint32_t* src, int num_pixels, uint8_t* dst);
void VP8LConvertBGRAToRGBA_C(const uint32_t* src, int num_pixels, uint8_t* dst);
void VP8LConvertBGRAToRGBA4444_C(const uint32_t* src,
int num_pixels, uint8_t* dst);
void VP8LConvertBGRAToRGB565_C(const uint32_t* src,
int num_pixels, uint8_t* dst);
void VP8LConvertBGRAToBGR_C(const uint32_t* src, int num_pixels, uint8_t* dst);
void VP8LAddGreenToBlueAndRed_C(uint32_t* data, int num_pixels);
// Must be called before calling any of the above methods.
void VP8LDspInit(void);
//------------------------------------------------------------------------------
// Encoding
extern VP8LProcessBlueAndRedFunc VP8LSubtractGreenFromBlueAndRed;
extern VP8LTransformColorFunc VP8LTransformColor;
typedef void (*VP8LCollectColorBlueTransformsFunc)(
const uint32_t* argb, int stride,
int tile_width, int tile_height,
int green_to_blue, int red_to_blue, int histo[]);
extern VP8LCollectColorBlueTransformsFunc VP8LCollectColorBlueTransforms;
typedef void (*VP8LCollectColorRedTransformsFunc)(
const uint32_t* argb, int stride,
int tile_width, int tile_height,
int green_to_red, int histo[]);
extern VP8LCollectColorRedTransformsFunc VP8LCollectColorRedTransforms;
// Expose some C-only fallback functions
void VP8LTransformColor_C(const VP8LMultipliers* const m,
uint32_t* data, int num_pixels);
void VP8LSubtractGreenFromBlueAndRed_C(uint32_t* argb_data, int num_pixels);
void VP8LCollectColorRedTransforms_C(const uint32_t* argb, int stride,
int tile_width, int tile_height,
int green_to_red, int histo[]);
void VP8LCollectColorBlueTransforms_C(const uint32_t* argb, int stride,
int tile_width, int tile_height,
int green_to_blue, int red_to_blue,
int histo[]);
//------------------------------------------------------------------------------
// Image transforms.
void VP8LResidualImage(int width, int height, int bits, int low_effort,
uint32_t* const argb, uint32_t* const argb_scratch,
uint32_t* const image, int exact);
void VP8LColorSpaceTransform(int width, int height, int bits, int quality,
uint32_t* const argb, uint32_t* image);
//------------------------------------------------------------------------------
// Misc methods.
// Computes sampled size of 'size' when sampling using 'sampling bits'.
static WEBP_INLINE uint32_t VP8LSubSampleSize(uint32_t size,
uint32_t sampling_bits) {
return (size + (1 << sampling_bits) - 1) >> sampling_bits;
}
// -----------------------------------------------------------------------------
// Faster logarithm for integers. Small values use a look-up table.
#define LOG_LOOKUP_IDX_MAX 256
extern const float kLog2Table[LOG_LOOKUP_IDX_MAX];
extern const float kSLog2Table[LOG_LOOKUP_IDX_MAX];
typedef float (*VP8LFastLog2SlowFunc)(uint32_t v);
extern VP8LFastLog2SlowFunc VP8LFastLog2Slow;
extern VP8LFastLog2SlowFunc VP8LFastSLog2Slow;
static WEBP_INLINE float VP8LFastLog2(uint32_t v) {
return (v < LOG_LOOKUP_IDX_MAX) ? kLog2Table[v] : VP8LFastLog2Slow(v);
}
// Fast calculation of v * log2(v) for integer input.
static WEBP_INLINE float VP8LFastSLog2(uint32_t v) {
return (v < LOG_LOOKUP_IDX_MAX) ? kSLog2Table[v] : VP8LFastSLog2Slow(v);
}
// -----------------------------------------------------------------------------
// Huffman-cost related functions.
typedef double (*VP8LCostFunc)(const uint32_t* population, int length);
typedef double (*VP8LCostCombinedFunc)(const uint32_t* X, const uint32_t* Y,
int length);
extern VP8LCostFunc VP8LExtraCost;
extern VP8LCostCombinedFunc VP8LExtraCostCombined;
typedef struct { // small struct to hold counters
int counts[2]; // index: 0=zero steak, 1=non-zero streak
int streaks[2][2]; // [zero/non-zero][streak<3 / streak>=3]
} VP8LStreaks;
typedef VP8LStreaks (*VP8LCostCountFunc)(const uint32_t* population,
int length);
typedef VP8LStreaks (*VP8LCostCombinedCountFunc)(const uint32_t* X,
const uint32_t* Y, int length);
extern VP8LCostCountFunc VP8LHuffmanCostCount;
extern VP8LCostCombinedCountFunc VP8LHuffmanCostCombinedCount;
// Get the symbol entropy for the distribution 'population'.
// Set 'trivial_sym', if there's only one symbol present in the distribution.
double VP8LPopulationCost(const uint32_t* const population, int length,
uint32_t* const trivial_sym);
// Get the combined symbol entropy for the distributions 'X' and 'Y'.
double VP8LGetCombinedEntropy(const uint32_t* const X,
const uint32_t* const Y, int length);
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);
// This function estimates the cost in bits excluding the bits needed to
// represent the entropy code itself.
double VP8LHistogramEstimateBitsBulk(const VP8LHistogram* const p);
typedef void (*VP8LHistogramAddFunc)(const VP8LHistogram* const a,
const VP8LHistogram* const b,
VP8LHistogram* const out);
extern VP8LHistogramAddFunc VP8LHistogramAdd;
// -----------------------------------------------------------------------------
// PrefixEncode()
static WEBP_INLINE int VP8LBitsLog2Ceiling(uint32_t n) {
const int log_floor = BitsLog2Floor(n);
if (n == (n & ~(n - 1))) // zero or a power of two.
return log_floor;
else
return log_floor + 1;
}
// Splitting of distance and length codes into prefixes and
// extra bits. The prefixes are encoded with an entropy code
// while the extra bits are stored just as normal bits.
static WEBP_INLINE void VP8LPrefixEncodeBitsNoLUT(int distance, int* const code,
int* const extra_bits) {
const int highest_bit = BitsLog2Floor(--distance);
const int second_highest_bit = (distance >> (highest_bit - 1)) & 1;
*extra_bits = highest_bit - 1;
*code = 2 * highest_bit + second_highest_bit;
}
static WEBP_INLINE void VP8LPrefixEncodeNoLUT(int distance, int* const code,
int* const extra_bits,
int* const extra_bits_value) {
const int highest_bit = BitsLog2Floor(--distance);
const int second_highest_bit = (distance >> (highest_bit - 1)) & 1;
*extra_bits = highest_bit - 1;
*extra_bits_value = distance & ((1 << *extra_bits) - 1);
*code = 2 * highest_bit + second_highest_bit;
}
#define PREFIX_LOOKUP_IDX_MAX 512
typedef struct {
int8_t code_;
int8_t extra_bits_;
} VP8LPrefixCode;
// These tables are derived using VP8LPrefixEncodeNoLUT.
extern const VP8LPrefixCode kPrefixEncodeCode[PREFIX_LOOKUP_IDX_MAX];
extern const uint8_t kPrefixEncodeExtraBitsValue[PREFIX_LOOKUP_IDX_MAX];
static WEBP_INLINE void VP8LPrefixEncodeBits(int distance, int* const code,
int* const extra_bits) {
if (distance < PREFIX_LOOKUP_IDX_MAX) {
const VP8LPrefixCode prefix_code = kPrefixEncodeCode[distance];
*code = prefix_code.code_;
*extra_bits = prefix_code.extra_bits_;
} else {
VP8LPrefixEncodeBitsNoLUT(distance, code, extra_bits);
}
}
static WEBP_INLINE void VP8LPrefixEncode(int distance, int* const code,
int* const extra_bits,
int* const extra_bits_value) {
if (distance < PREFIX_LOOKUP_IDX_MAX) {
const VP8LPrefixCode prefix_code = kPrefixEncodeCode[distance];
*code = prefix_code.code_;
*extra_bits = prefix_code.extra_bits_;
*extra_bits_value = kPrefixEncodeExtraBitsValue[distance];
} else {
VP8LPrefixEncodeNoLUT(distance, code, extra_bits, extra_bits_value);
}
}
// In-place difference of each component with mod 256.
static WEBP_INLINE uint32_t VP8LSubPixels(uint32_t a, uint32_t b) {
const uint32_t alpha_and_green =
0x00ff00ffu + (a & 0xff00ff00u) - (b & 0xff00ff00u);
const uint32_t red_and_blue =
0xff00ff00u + (a & 0x00ff00ffu) - (b & 0x00ff00ffu);
return (alpha_and_green & 0xff00ff00u) | (red_and_blue & 0x00ff00ffu);
}
void VP8LBundleColorMap(const uint8_t* const row, int width,
int xbits, uint32_t* const dst);
// Must be called before calling any of the above methods.
void VP8LEncDspInit(void);
//------------------------------------------------------------------------------
#ifdef __cplusplus
} // extern "C"
#endif
#endif // WEBP_DSP_LOSSLESS_H_
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