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webp/src/dsp/lossless.c

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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/
// -----------------------------------------------------------------------------
//
// Image transforms and color space conversion methods for lossless decoder.
//
// Authors: Vikas Arora (vikaas.arora@gmail.com)
// jyrki@google.com (Jyrki Alakuijala)
// Urvang Joshi (urvang@google.com)
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif
#include <math.h>
#include <stdlib.h>
#include "./lossless.h"
#include "../dec/vp8li.h"
#ifdef USE_LOSSLESS_ENCODER
#include "../enc/histogram.h"
// A lookup table for small values of log(int) to be used in entropy
// computation.
//
// ", ".join(["%.16ff" % x for x in [0.0]+[log(x) for x in range(1, 256)]])
#define LOG_LOOKUP_IDX_MAX 256
static const float kLogTable[LOG_LOOKUP_IDX_MAX] = {
0.0000000000000000f, 0.0000000000000000f, 0.6931471805599453f,
1.0986122886681098f, 1.3862943611198906f, 1.6094379124341003f,
1.7917594692280550f, 1.9459101490553132f, 2.0794415416798357f,
2.1972245773362196f, 2.3025850929940459f, 2.3978952727983707f,
2.4849066497880004f, 2.5649493574615367f, 2.6390573296152584f,
2.7080502011022101f, 2.7725887222397811f, 2.8332133440562162f,
2.8903717578961645f, 2.9444389791664403f, 2.9957322735539909f,
3.0445224377234230f, 3.0910424533583161f, 3.1354942159291497f,
3.1780538303479458f, 3.2188758248682006f, 3.2580965380214821f,
3.2958368660043291f, 3.3322045101752038f, 3.3672958299864741f,
3.4011973816621555f, 3.4339872044851463f, 3.4657359027997265f,
3.4965075614664802f, 3.5263605246161616f, 3.5553480614894135f,
3.5835189384561099f, 3.6109179126442243f, 3.6375861597263857f,
3.6635616461296463f, 3.6888794541139363f, 3.7135720667043080f,
3.7376696182833684f, 3.7612001156935624f, 3.7841896339182610f,
3.8066624897703196f, 3.8286413964890951f, 3.8501476017100584f,
3.8712010109078911f, 3.8918202981106265f, 3.9120230054281460f,
3.9318256327243257f, 3.9512437185814275f, 3.9702919135521220f,
3.9889840465642745f, 4.0073331852324712f, 4.0253516907351496f,
4.0430512678345503f, 4.0604430105464191f, 4.0775374439057197f,
4.0943445622221004f, 4.1108738641733114f, 4.1271343850450917f,
4.1431347263915326f, 4.1588830833596715f, 4.1743872698956368f,
4.1896547420264252f, 4.2046926193909657f, 4.2195077051761070f,
4.2341065045972597f, 4.2484952420493594f, 4.2626798770413155f,
4.2766661190160553f, 4.2904594411483910f, 4.3040650932041702f,
4.3174881135363101f, 4.3307333402863311f, 4.3438054218536841f,
4.3567088266895917f, 4.3694478524670215f, 4.3820266346738812f,
4.3944491546724391f, 4.4067192472642533f, 4.4188406077965983f,
4.4308167988433134f, 4.4426512564903167f, 4.4543472962535073f,
4.4659081186545837f, 4.4773368144782069f, 4.4886363697321396f,
4.4998096703302650f, 4.5108595065168497f, 4.5217885770490405f,
4.5325994931532563f, 4.5432947822700038f, 4.5538768916005408f,
4.5643481914678361f, 4.5747109785033828f, 4.5849674786705723f,
4.5951198501345898f, 4.6051701859880918f, 4.6151205168412597f,
4.6249728132842707f, 4.6347289882296359f, 4.6443908991413725f,
4.6539603501575231f, 4.6634390941120669f, 4.6728288344619058f,
4.6821312271242199f, 4.6913478822291435f, 4.7004803657924166f,
4.7095302013123339f, 4.7184988712950942f, 4.7273878187123408f,
4.7361984483944957f, 4.7449321283632502f, 4.7535901911063645f,
4.7621739347977563f, 4.7706846244656651f, 4.7791234931115296f,
4.7874917427820458f, 4.7957905455967413f, 4.8040210447332568f,
4.8121843553724171f, 4.8202815656050371f, 4.8283137373023015f,
4.8362819069514780f, 4.8441870864585912f, 4.8520302639196169f,
4.8598124043616719f, 4.8675344504555822f, 4.8751973232011512f,
4.8828019225863706f, 4.8903491282217537f, 4.8978397999509111f,
4.9052747784384296f, 4.9126548857360524f, 4.9199809258281251f,
4.9272536851572051f, 4.9344739331306915f, 4.9416424226093039f,
4.9487598903781684f, 4.9558270576012609f, 4.9628446302599070f,
4.9698132995760007f, 4.9767337424205742f, 4.9836066217083363f,
4.9904325867787360f, 4.9972122737641147f, 5.0039463059454592f,
5.0106352940962555f, 5.0172798368149243f, 5.0238805208462765f,
5.0304379213924353f, 5.0369526024136295f, 5.0434251169192468f,
5.0498560072495371f, 5.0562458053483077f, 5.0625950330269669f,
5.0689042022202315f, 5.0751738152338266f, 5.0814043649844631f,
5.0875963352323836f, 5.0937502008067623f, 5.0998664278241987f,
5.1059454739005803f, 5.1119877883565437f, 5.1179938124167554f,
5.1239639794032588f, 5.1298987149230735f, 5.1357984370502621f,
5.1416635565026603f, 5.1474944768134527f, 5.1532915944977793f,
5.1590552992145291f, 5.1647859739235145f, 5.1704839950381514f,
5.1761497325738288f, 5.1817835502920850f, 5.1873858058407549f,
5.1929568508902104f, 5.1984970312658261f, 5.2040066870767951f,
5.2094861528414214f, 5.2149357576089859f, 5.2203558250783244f,
5.2257466737132017f, 5.2311086168545868f, 5.2364419628299492f,
5.2417470150596426f, 5.2470240721604862f, 5.2522734280466299f,
5.2574953720277815f, 5.2626901889048856f, 5.2678581590633282f,
5.2729995585637468f, 5.2781146592305168f, 5.2832037287379885f,
5.2882670306945352f, 5.2933048247244923f, 5.2983173665480363f,
5.3033049080590757f, 5.3082676974012051f, 5.3132059790417872f,
5.3181199938442161f, 5.3230099791384085f, 5.3278761687895813f,
5.3327187932653688f, 5.3375380797013179f, 5.3423342519648109f,
5.3471075307174685f, 5.3518581334760666f, 5.3565862746720123f,
5.3612921657094255f, 5.3659760150218512f, 5.3706380281276624f,
5.3752784076841653f, 5.3798973535404597f, 5.3844950627890888f,
5.3890717298165010f, 5.3936275463523620f, 5.3981627015177525f,
5.4026773818722793f, 5.4071717714601188f, 5.4116460518550396f,
5.4161004022044201f, 5.4205349992722862f, 5.4249500174814029f,
5.4293456289544411f, 5.4337220035542400f, 5.4380793089231956f,
5.4424177105217932f, 5.4467373716663099f, 5.4510384535657002f,
5.4553211153577017f, 5.4595855141441589f, 5.4638318050256105f,
5.4680601411351315f, 5.4722706736714750f, 5.4764635519315110f,
5.4806389233419912f, 5.4847969334906548f, 5.4889377261566867f,
5.4930614433405482f, 5.4971682252932021f, 5.5012582105447274f,
5.5053315359323625f, 5.5093883366279774f, 5.5134287461649825f,
5.5174528964647074f, 5.5214609178622460f, 5.5254529391317835f,
5.5294290875114234f, 5.5333894887275203f, 5.5373342670185366f,
5.5412635451584258f
};
#define APPROX_LOG_MAX 4096
#define LOG_2_BASE_E 0.6931471805599453f
float VP8LFastLog(int v) {
if (v < APPROX_LOG_MAX) {
int log_cnt = 0;
while (v >= LOG_LOOKUP_IDX_MAX) {
++log_cnt;
v = v >> 1;
}
return kLogTable[v] + (log_cnt * LOG_2_BASE_E);
}
return log(v);
}
#endif
//------------------------------------------------------------------------------
// Image transforms.
// In-place sum of each component with mod 256.
static WEBP_INLINE void AddPixelsEq(uint32_t* a, uint32_t b) {
const uint32_t alpha_and_green = (*a & 0xff00ff00u) + (b & 0xff00ff00u);
const uint32_t red_and_blue = (*a & 0x00ff00ffu) + (b & 0x00ff00ffu);
*a = (alpha_and_green & 0xff00ff00u) | (red_and_blue & 0x00ff00ffu);
}
static WEBP_INLINE uint32_t Average2(uint32_t a0, uint32_t a1) {
return (((a0 ^ a1) & 0xfefefefeL) >> 1) + (a0 & a1);
}
static WEBP_INLINE uint32_t Average3(uint32_t a0, uint32_t a1, uint32_t a2) {
return Average2(Average2(a0, a2), a1);
}
static WEBP_INLINE uint32_t Average4(uint32_t a0, uint32_t a1,
uint32_t a2, uint32_t a3) {
return Average2(Average2(a0, a1), Average2(a2, a3));
}
static WEBP_INLINE uint32_t Clip255(uint32_t a) {
if (a < 256) {
return a;
}
// return 0, when a is a negative integer.
// return 255, when a is positive.
return ~a >> 24;
}
static WEBP_INLINE int AddSubtractComponentFull(int a, int b, int c) {
return Clip255(a + b - c);
}
static WEBP_INLINE uint32_t ClampedAddSubtractFull(uint32_t c0, uint32_t c1,
uint32_t c2) {
const int a = AddSubtractComponentFull(c0 >> 24, c1 >> 24, c2 >> 24);
const int r = AddSubtractComponentFull((c0 >> 16) & 0xff,
(c1 >> 16) & 0xff,
(c2 >> 16) & 0xff);
const int g = AddSubtractComponentFull((c0 >> 8) & 0xff,
(c1 >> 8) & 0xff,
(c2 >> 8) & 0xff);
const int b = AddSubtractComponentFull(c0 & 0xff, c1 & 0xff, c2 & 0xff);
return (a << 24) | (r << 16) | (g << 8) | b;
}
static WEBP_INLINE int AddSubtractComponentHalf(int a, int b) {
return Clip255(a + (a - b) / 2);
}
static WEBP_INLINE uint32_t ClampedAddSubtractHalf(uint32_t c0, uint32_t c1,
uint32_t c2) {
const uint32_t ave = Average2(c0, c1);
const int a = AddSubtractComponentHalf(ave >> 24, c2 >> 24);
const int r = AddSubtractComponentHalf((ave >> 16) & 0xff, (c2 >> 16) & 0xff);
const int g = AddSubtractComponentHalf((ave >> 8) & 0xff, (c2 >> 8) & 0xff);
const int b = AddSubtractComponentHalf((ave >> 0) & 0xff, (c2 >> 0) & 0xff);
return (a << 24) | (r << 16) | (g << 8) | b;
}
static WEBP_INLINE int Sub3(int a, int b, int c) {
const int pa = b - c;
const int pb = a - c;
return abs(pa) - abs(pb);
}
static WEBP_INLINE uint32_t Select(uint32_t a, uint32_t b, uint32_t c) {
const int pa_minus_pb =
Sub3((a >> 24) , (b >> 24) , (c >> 24) ) +
Sub3((a >> 16) & 0xff, (b >> 16) & 0xff, (c >> 16) & 0xff) +
Sub3((a >> 8) & 0xff, (b >> 8) & 0xff, (c >> 8) & 0xff) +
Sub3((a ) & 0xff, (b ) & 0xff, (c ) & 0xff);
return (pa_minus_pb <= 0) ? a : b;
}
//------------------------------------------------------------------------------
// Predictors
static uint32_t Predictor0(uint32_t left, const uint32_t* const top) {
(void)top;
(void)left;
return ARGB_BLACK;
}
static uint32_t Predictor1(uint32_t left, const uint32_t* const top) {
(void)top;
return left;
}
static uint32_t Predictor2(uint32_t left, const uint32_t* const top) {
(void)left;
return top[0];
}
static uint32_t Predictor3(uint32_t left, const uint32_t* const top) {
(void)left;
return top[1];
}
static uint32_t Predictor4(uint32_t left, const uint32_t* const top) {
(void)left;
return top[-1];
}
static uint32_t Predictor5(uint32_t left, const uint32_t* const top) {
const uint32_t pred = Average3(left, top[0], top[1]);
return pred;
}
static uint32_t Predictor6(uint32_t left, const uint32_t* const top) {
const uint32_t pred = Average2(left, top[-1]);
return pred;
}
static uint32_t Predictor7(uint32_t left, const uint32_t* const top) {
const uint32_t pred = Average2(left, top[0]);
return pred;
}
static uint32_t Predictor8(uint32_t left, const uint32_t* const top) {
const uint32_t pred = Average2(top[-1], top[0]);
(void)left;
return pred;
}
static uint32_t Predictor9(uint32_t left, const uint32_t* const top) {
const uint32_t pred = Average2(top[0], top[1]);
(void)left;
return pred;
}
static uint32_t Predictor10(uint32_t left, const uint32_t* const top) {
const uint32_t pred = Average4(left, top[-1], top[0], top[1]);
return pred;
}
static uint32_t Predictor11(uint32_t left, const uint32_t* const top) {
const uint32_t pred = Select(top[0], left, top[-1]);
return pred;
}
static uint32_t Predictor12(uint32_t left, const uint32_t* const top) {
const uint32_t pred = ClampedAddSubtractFull(left, top[0], top[-1]);
return pred;
}
static uint32_t Predictor13(uint32_t left, const uint32_t* const top) {
const uint32_t pred = ClampedAddSubtractHalf(left, top[0], top[-1]);
return pred;
}
typedef uint32_t (*PredictorFunc)(uint32_t left, const uint32_t* const top);
static const PredictorFunc kPredictors[16] = {
Predictor0, Predictor1, Predictor2, Predictor3,
Predictor4, Predictor5, Predictor6, Predictor7,
Predictor8, Predictor9, Predictor10, Predictor11,
Predictor12, Predictor13,
Predictor0, Predictor0 // <- padding security sentinels
};
#ifdef USE_LOSSLESS_ENCODER
// TODO(vikasa): Replace 256 etc with defines.
static double PredictionCostSpatial(const int* counts,
int weight_0, double exp_val) {
const int significant_symbols = 16;
const double exp_decay_factor = 0.6;
double bits = weight_0 * counts[0];
int i;
for (i = 1; i < significant_symbols; ++i) {
bits += exp_val * (counts[i] + counts[256 - i]);
exp_val *= exp_decay_factor;
}
return -0.1 * bits;
}
// Compute the Shanon's entropy: Sum(p*log2(p))
static double ShannonEntropy(const int* const array, int n) {
int i;
double retval = 0;
int sum = 0;
for (i = 0; i < n; ++i) {
if (array[i] != 0) {
sum += array[i];
retval += array[i] * VP8LFastLog(array[i]);
}
}
retval -= sum * VP8LFastLog(sum);
retval *= -1.4426950408889634; // 1.0 / -FastLog(2);
return retval;
}
static double PredictionCostSpatialHistogram(int accumulated[4][256],
int tile[4][256]) {
int i;
int k;
int combo[256];
double retval = 0;
for (i = 0; i < 4; ++i) {
const double exp_val = 0.94;
retval += PredictionCostSpatial(&tile[i][0], 1, exp_val);
retval += ShannonEntropy(&tile[i][0], 256);
for (k = 0; k < 256; ++k) {
combo[k] = accumulated[i][k] + tile[i][k];
}
retval += ShannonEntropy(&combo[0], 256);
}
return retval;
}
static int GetBestPredictorForTile(int width, int height,
int tile_x, int tile_y, int bits,
int accumulated[4][256],
const uint32_t* const argb_scratch) {
const int kNumPredModes = 14;
const int col_start = tile_x << bits;
const int row_start = tile_y << bits;
const int tile_size = 1 << bits;
const int ymax = (tile_size <= height - row_start) ?
tile_size : height - row_start;
const int xmax = (tile_size <= width - col_start) ?
tile_size : width - col_start;
int histo[4][256];
double best_diff = 1e99;
int best_mode = 0;
int mode;
for (mode = 0; mode < kNumPredModes; ++mode) {
const uint32_t* current_row = argb_scratch;
const PredictorFunc pred_func = kPredictors[mode];
double cur_diff;
int y;
memset(&histo[0][0], 0, sizeof(histo));
for (y = 0; y < ymax; ++y) {
int x;
const int row = row_start + y;
const uint32_t* const upper_row = current_row;
current_row = upper_row + width;
for (x = 0; x < xmax; ++x) {
const int col = col_start + x;
uint32_t predict;
uint32_t predict_diff;
if (row == 0) {
predict = (col == 0) ? ARGB_BLACK : current_row[col - 1]; // Left.
} else if (col == 0) {
predict = upper_row[col]; // Top.
} else {
predict = pred_func(current_row[col - 1], upper_row + col);
}
predict_diff = VP8LSubPixels(current_row[col], predict);
++histo[0][predict_diff >> 24];
++histo[1][((predict_diff >> 16) & 0xff)];
++histo[2][((predict_diff >> 8) & 0xff)];
++histo[3][(predict_diff & 0xff)];
}
}
cur_diff = PredictionCostSpatialHistogram(accumulated, histo);
if (cur_diff < best_diff) {
best_diff = cur_diff;
best_mode = mode;
}
}
return best_mode;
}
static void CopyTileWithPrediction(int width, int height,
int tile_x, int tile_y, int bits, int mode,
const uint32_t* const argb_scratch,
uint32_t* const argb) {
const int col_start = tile_x << bits;
const int row_start = tile_y << bits;
const int tile_size = 1 << bits;
const int ymax = (tile_size <= height - row_start) ?
tile_size : height - row_start;
const int xmax = (tile_size <= width - col_start) ?
tile_size : width - col_start;
const PredictorFunc pred_func = kPredictors[mode];
const uint32_t* current_row = argb_scratch;
int y;
for (y = 0; y < ymax; ++y) {
int x;
const int row = row_start + y;
const uint32_t* const upper_row = current_row;
current_row = upper_row + width;
for (x = 0; x < xmax; ++x) {
const int col = col_start + x;
const int pix = row * width + col;
uint32_t predict;
if (row == 0) {
predict = (col == 0) ? ARGB_BLACK : current_row[col - 1]; // Left.
} else if (col == 0) {
predict = upper_row[col]; // Top.
} else {
predict = pred_func(current_row[col - 1], upper_row + col);
}
argb[pix] = VP8LSubPixels(current_row[col], predict);
}
}
}
void VP8LResidualImage(int width, int height, int bits,
uint32_t* const argb, uint32_t* const argb_scratch,
uint32_t* const image) {
const int max_tile_size = 1 << bits;
const int tiles_per_row = VP8LSubSampleSize(width, bits);
const int tiles_per_col = VP8LSubSampleSize(height, bits);
uint32_t* const upper_row = argb_scratch;
uint32_t* const current_tile_rows = argb_scratch + width;
int tile_y;
int histo[4][256];
memset(histo, 0, sizeof(histo));
for (tile_y = 0; tile_y < tiles_per_col; ++tile_y) {
const int tile_y_offset = tile_y * max_tile_size;
const int this_tile_height =
(tile_y < tiles_per_col - 1) ? max_tile_size : height - tile_y_offset;
int tile_x;
if (tile_y > 0) {
memcpy(upper_row, current_tile_rows + (max_tile_size - 1) * width,
width * sizeof(*upper_row));
}
memcpy(current_tile_rows, &argb[tile_y_offset * width],
this_tile_height * width * sizeof(*current_tile_rows));
for (tile_x = 0; tile_x < tiles_per_row; ++tile_x) {
int pred;
int y;
const int tile_x_offset = tile_x * max_tile_size;
int all_x_max = tile_x_offset + max_tile_size;
if (all_x_max > width) {
all_x_max = width;
}
pred = GetBestPredictorForTile(width, height, tile_x, tile_y, bits, histo,
argb_scratch);
image[tile_y * tiles_per_row + tile_x] = 0xff000000u | (pred << 8);
CopyTileWithPrediction(width, height, tile_x, tile_y, bits, pred,
argb_scratch, argb);
for (y = 0; y < max_tile_size; ++y) {
int ix;
int all_x;
int all_y = tile_y_offset + y;
if (all_y >= height) {
break;
}
ix = all_y * width + tile_x_offset;
for (all_x = tile_x_offset; all_x < all_x_max; ++all_x, ++ix) {
const uint32_t a = argb[ix];
++histo[0][a >> 24];
++histo[1][((a >> 16) & 0xff)];
++histo[2][((a >> 8) & 0xff)];
++histo[3][(a & 0xff)];
}
}
}
}
}
#endif
// Inverse prediction.
static void PredictorInverseTransform(const VP8LTransform* const transform,
int y_start, int y_end, uint32_t* data) {
const int width = transform->xsize_;
if (y_start == 0) { // First Row follows the L (mode=1) mode.
int x;
const uint32_t pred0 = Predictor0(data[-1], NULL);
AddPixelsEq(data, pred0);
for (x = 1; x < width; ++x) {
const uint32_t pred1 = Predictor1(data[x - 1], NULL);
AddPixelsEq(data + x, pred1);
}
data += width;
++y_start;
}
{
int y = y_start;
const int mask = (1 << transform->bits_) - 1;
const int tiles_per_row = VP8LSubSampleSize(width, transform->bits_);
const uint32_t* pred_mode_base =
transform->data_ + (y >> transform->bits_) * tiles_per_row;
while (y < y_end) {
int x;
const uint32_t pred2 = Predictor2(data[-1], data - width);
const uint32_t* pred_mode_src = pred_mode_base;
PredictorFunc pred_func;
// First pixel follows the T (mode=2) mode.
AddPixelsEq(data, pred2);
// .. the rest:
pred_func = kPredictors[((*pred_mode_src++) >> 8) & 0xf];
for (x = 1; x < width; ++x) {
uint32_t pred;
if ((x & mask) == 0) { // start of tile. Read predictor function.
pred_func = kPredictors[((*pred_mode_src++) >> 8) & 0xf];
}
pred = pred_func(data[x - 1], data + x - width);
AddPixelsEq(data + x, pred);
}
data += width;
++y;
if ((y & mask) == 0) { // Use the same mask, since tiles are squares.
pred_mode_base += tiles_per_row;
}
}
}
}
#ifdef USE_LOSSLESS_ENCODER
void VP8LSubtractGreenFromBlueAndRed(uint32_t* argb_data, int num_pixs) {
int i;
for (i = 0; i < num_pixs; ++i) {
const uint32_t argb = argb_data[i];
const uint32_t green = (argb >> 8) & 0xff;
const uint32_t new_r = (((argb >> 16) & 0xff) - green) & 0xff;
const uint32_t new_b = ((argb & 0xff) - green) & 0xff;
argb_data[i] = (argb & 0xff00ff00) | (new_r << 16) | new_b;
}
}
#endif
// Add green to blue and red channels (i.e. perform the inverse transform of
// 'subtract green').
static void AddGreenToBlueAndRed(const VP8LTransform* const transform,
int y_start, int y_end, uint32_t* data) {
const int width = transform->xsize_;
const uint32_t* const data_end = data + (y_end - y_start) * width;
while (data < data_end) {
const uint32_t argb = *data;
// "* 0001001u" is equivalent to "(green << 16) + green)"
const uint32_t green = ((argb >> 8) & 0xff);
uint32_t red_blue = (argb & 0x00ff00ffu);
red_blue += (green << 16) | green;
red_blue &= 0x00ff00ffu;
*data++ = (argb & 0xff00ff00u) | red_blue;
}
}
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_;
} Multipliers;
static WEBP_INLINE void MultipliersClear(Multipliers* m) {
m->green_to_red_ = 0;
m->green_to_blue_ = 0;
m->red_to_blue_ = 0;
}
static WEBP_INLINE uint32_t ColorTransformDelta(int8_t color_pred,
int8_t color) {
return (uint32_t)((int)(color_pred) * color) >> 5;
}
static WEBP_INLINE void ColorCodeToMultipliers(uint32_t color_code,
Multipliers* const m) {
m->green_to_red_ = (color_code >> 0) & 0xff;
m->green_to_blue_ = (color_code >> 8) & 0xff;
m->red_to_blue_ = (color_code >> 16) & 0xff;
}
static WEBP_INLINE uint32_t MultipliersToColorCode(Multipliers* const m) {
return 0xff000000u |
((uint32_t)(m->red_to_blue_) << 16) |
((uint32_t)(m->green_to_blue_) << 8) |
m->green_to_red_;
}
static WEBP_INLINE uint32_t TransformColor(const Multipliers* const m,
uint32_t argb, int inverse) {
const uint32_t green = argb >> 8;
const uint32_t red = argb >> 16;
uint32_t new_red = red;
uint32_t new_blue = argb;
if (inverse) {
new_red += ColorTransformDelta(m->green_to_red_, green);
new_red &= 0xff;
new_blue += ColorTransformDelta(m->green_to_blue_, green);
new_blue += ColorTransformDelta(m->red_to_blue_, new_red);
new_blue &= 0xff;
} else {
new_red -= ColorTransformDelta(m->green_to_red_, green);
new_red &= 0xff;
new_blue -= ColorTransformDelta(m->green_to_blue_, green);
new_blue -= ColorTransformDelta(m->red_to_blue_, red);
new_blue &= 0xff;
}
return (argb & 0xff00ff00u) | (new_red << 16) | (new_blue);
}
#ifdef USE_LOSSLESS_ENCODER
static WEBP_INLINE int SkipRepeatedPixels(const uint32_t* const argb,
int ix, int xsize) {
const uint32_t v = argb[ix];
if (ix >= xsize + 3) {
if (v == argb[ix - xsize] &&
argb[ix - 1] == argb[ix - xsize - 1] &&
argb[ix - 2] == argb[ix - xsize - 2] &&
argb[ix - 3] == argb[ix - xsize - 3]) {
return 1;
}
return v == argb[ix - 3] && v == argb[ix - 2] && v == argb[ix - 1];
} else if (ix >= 3) {
return v == argb[ix - 3] && v == argb[ix - 2] && v == argb[ix - 1];
}
return 0;
}
static double PredictionCostCrossColor(const int accumulated[256],
const int counts[256]) {
// Favor low entropy, locally and globally.
int i;
int combo[256];
for (i = 0; i < 256; ++i) {
combo[i] = accumulated[i] + counts[i];
}
return ShannonEntropy(combo, 256) +
ShannonEntropy(counts, 256) +
PredictionCostSpatial(counts, 3, 2.4); // Favor small absolute values.
}
static Multipliers GetBestColorTransformForTile(
int tile_x, int tile_y, int bits,
Multipliers prevX,
Multipliers prevY,
int step, int xsize, int ysize,
int* accumulated_red_histo,
int* accumulated_blue_histo,
const uint32_t* const argb) {
double best_diff = 1e99;
double cur_diff;
const int halfstep = step / 2;
const int max_tile_size = 1 << bits;
const int tile_y_offset = tile_y * max_tile_size;
const int tile_x_offset = tile_x * max_tile_size;
int green_to_red;
int green_to_blue;
int red_to_blue;
int all_x_max = tile_x_offset + max_tile_size;
int all_y_max = tile_y_offset + max_tile_size;
Multipliers best_tx;
MultipliersClear(&best_tx);
if (all_x_max > xsize) {
all_x_max = xsize;
}
if (all_y_max > ysize) {
all_y_max = ysize;
}
for (green_to_red = -64; green_to_red <= 64; green_to_red += halfstep) {
int histo[256] = { 0 };
int all_y;
Multipliers tx;
MultipliersClear(&tx);
tx.green_to_red_ = green_to_red & 0xff;
for (all_y = tile_y_offset; all_y < all_y_max; ++all_y) {
uint32_t predict;
int ix = all_y * xsize + tile_x_offset;
int all_x;
for (all_x = tile_x_offset; all_x < all_x_max; ++all_x, ++ix) {
if (SkipRepeatedPixels(argb, ix, xsize)) {
continue;
}
predict = TransformColor(&tx, argb[ix], 0);
++histo[(predict >> 16) & 0xff]; // red.
}
}
cur_diff = PredictionCostCrossColor(&accumulated_red_histo[0], &histo[0]);
if (tx.green_to_red_ == prevX.green_to_red_) {
cur_diff -= 3; // favor keeping the areas locally similar
}
if (tx.green_to_red_ == prevY.green_to_red_) {
cur_diff -= 3; // favor keeping the areas locally similar
}
if (tx.green_to_red_ == 0) {
cur_diff -= 3;
}
if (cur_diff < best_diff) {
best_diff = cur_diff;
best_tx = tx;
}
}
best_diff = 1e99;
green_to_red = best_tx.green_to_red_;
for (green_to_blue = -32; green_to_blue <= 32; green_to_blue += step) {
for (red_to_blue = -32; red_to_blue <= 32; red_to_blue += step) {
int all_y;
int histo[256] = { 0 };
Multipliers tx;
tx.green_to_red_ = green_to_red;
tx.green_to_blue_ = green_to_blue;
tx.red_to_blue_ = red_to_blue;
for (all_y = tile_y_offset; all_y < all_y_max; ++all_y) {
uint32_t predict;
int all_x;
int ix = all_y * xsize + tile_x_offset;
for (all_x = tile_x_offset; all_x < all_x_max; ++all_x, ++ix) {
if (SkipRepeatedPixels(argb, ix, xsize)) {
continue;
}
predict = TransformColor(&tx, argb[ix], 0);
++histo[predict & 0xff]; // blue.
}
}
cur_diff =
PredictionCostCrossColor(&accumulated_blue_histo[0], &histo[0]);
if (tx.green_to_blue_ == prevX.green_to_blue_) {
cur_diff -= 3; // favor keeping the areas locally similar
}
if (tx.green_to_blue_ == prevY.green_to_blue_) {
cur_diff -= 3; // favor keeping the areas locally similar
}
if (tx.red_to_blue_ == prevX.red_to_blue_) {
cur_diff -= 3; // favor keeping the areas locally similar
}
if (tx.red_to_blue_ == prevY.red_to_blue_) {
cur_diff -= 3; // favor keeping the areas locally similar
}
if (tx.green_to_blue_ == 0) {
cur_diff -= 3;
}
if (tx.red_to_blue_ == 0) {
cur_diff -= 3;
}
if (cur_diff < best_diff) {
best_diff = cur_diff;
best_tx = tx;
}
}
}
return best_tx;
}
static void CopyTileWithColorTransform(int xsize, int ysize,
int tile_x, int tile_y, int bits,
Multipliers color_transform,
uint32_t* const argb) {
int y;
int xscan = 1 << bits;
int yscan = 1 << bits;
tile_x <<= bits;
tile_y <<= bits;
if (xscan > xsize - tile_x) {
xscan = xsize - tile_x;
}
if (yscan > ysize - tile_y) {
yscan = ysize - tile_y;
}
yscan += tile_y;
for (y = tile_y; y < yscan; ++y) {
int ix = y * xsize + tile_x;
const int end_ix = ix + xscan;
for (; ix < end_ix; ++ix) {
argb[ix] = TransformColor(&color_transform, argb[ix], 0);
}
}
}
void VP8LColorSpaceTransform(int width, int height, int bits, int step,
uint32_t* const argb, uint32_t* image) {
const int max_tile_size = 1 << bits;
int tile_xsize = VP8LSubSampleSize(width, bits);
int tile_ysize = VP8LSubSampleSize(height, bits);
int accumulated_red_histo[256] = { 0 };
int accumulated_blue_histo[256] = { 0 };
int tile_y;
int tile_x;
Multipliers prevX;
Multipliers prevY;
MultipliersClear(&prevY);
MultipliersClear(&prevX);
for (tile_y = 0; tile_y < tile_ysize; ++tile_y) {
for (tile_x = 0; tile_x < tile_xsize; ++tile_x) {
Multipliers color_transform;
int all_x_max;
int y;
const int tile_y_offset = tile_y * max_tile_size;
const int tile_x_offset = tile_x * max_tile_size;
if (tile_y != 0) {
ColorCodeToMultipliers(image[tile_y * tile_xsize + tile_x - 1], &prevX);
ColorCodeToMultipliers(image[(tile_y - 1) * tile_xsize + tile_x],
&prevY);
} else if (tile_x != 0) {
ColorCodeToMultipliers(image[tile_y * tile_xsize + tile_x - 1], &prevX);
}
color_transform =
GetBestColorTransformForTile(tile_x, tile_y, bits,
prevX, prevY,
step, width, height,
&accumulated_red_histo[0],
&accumulated_blue_histo[0],
argb);
image[tile_y * tile_xsize + tile_x] =
MultipliersToColorCode(&color_transform);
CopyTileWithColorTransform(width, height, tile_x, tile_y, bits,
color_transform, argb);
// Gather accumulated histogram data.
all_x_max = tile_x_offset + max_tile_size;
if (all_x_max > width) {
all_x_max = width;
}
for (y = 0; y < max_tile_size; ++y) {
int ix;
int all_x;
int all_y = tile_y_offset + y;
if (all_y >= height) {
break;
}
ix = all_y * width + tile_x_offset;
for (all_x = tile_x_offset; all_x < all_x_max; ++all_x, ++ix) {
if (ix >= 2 &&
argb[ix] == argb[ix - 2] &&
argb[ix] == argb[ix - 1]) {
continue; // repeated pixels are handled by backward references
}
if (ix >= width + 2 &&
argb[ix - 2] == argb[ix - width - 2] &&
argb[ix - 1] == argb[ix - width - 1] &&
argb[ix] == argb[ix - width]) {
continue; // repeated pixels are handled by backward references
}
++accumulated_red_histo[(argb[ix] >> 16) & 0xff];
++accumulated_blue_histo[argb[ix] & 0xff];
}
}
}
}
}
#endif
// Color space inverse transform.
static void ColorSpaceInverseTransform(const VP8LTransform* const transform,
int y_start, int y_end, uint32_t* data) {
const int width = transform->xsize_;
const int mask = (1 << transform->bits_) - 1;
const int tiles_per_row = VP8LSubSampleSize(width, transform->bits_);
int y = y_start;
const uint32_t* pred_row =
transform->data_ + (y >> transform->bits_) * tiles_per_row;
while (y < y_end) {
const uint32_t* pred = pred_row;
Multipliers m = { 0, 0, 0 };
int x;
for (x = 0; x < width; ++x) {
if ((x & mask) == 0) ColorCodeToMultipliers(*pred++, &m);
data[x] = TransformColor(&m, data[x], 1);
}
data += width;
++y;
if ((y & mask) == 0) pred_row += tiles_per_row;;
}
}
// Separate out pixels packed together using pixel-bundling.
static void ColorIndexInverseTransform(
const VP8LTransform* const transform,
int y_start, int y_end, const uint32_t* src, uint32_t* dst) {
int y;
const int bits_per_pixel = 8 >> transform->bits_;
const int width = transform->xsize_;
const uint32_t* const color_map = transform->data_;
if (bits_per_pixel < 8) {
const int pixels_per_byte = 1 << transform->bits_;
const int count_mask = pixels_per_byte - 1;
const uint32_t bit_mask = (1 << bits_per_pixel) - 1;
for (y = y_start; y < y_end; ++y) {
uint32_t packed_pixels = 0;
int x;
for (x = 0; x < width; ++x) {
// We need to load fresh 'packed_pixels' once every 'bytes_per_pixels'
// increments of x. Fortunately, pixels_per_byte is a power of 2, so
// can just use a mask for that, instead of decrementing a counter.
if ((x & count_mask) == 0) packed_pixels = ((*src++) >> 8) & 0xff;
*dst++ = color_map[packed_pixels & bit_mask];
packed_pixels >>= bits_per_pixel;
}
}
} else {
for (y = y_start; y < y_end; ++y) {
int x;
for (x = 0; x < width; ++x) {
*dst++ = color_map[((*src++) >> 8) & 0xff];
}
}
}
}
void VP8LInverseTransform(const VP8LTransform* const transform,
int row_start, int row_end,
const uint32_t* const in, uint32_t* const out) {
assert(row_start < row_end);
assert(row_end <= transform->ysize_);
switch (transform->type_) {
case SUBTRACT_GREEN:
AddGreenToBlueAndRed(transform, row_start, row_end, out);
break;
case PREDICTOR_TRANSFORM:
PredictorInverseTransform(transform, row_start, row_end, out);
if (row_end != transform->ysize_) {
// The last predicted row in this iteration will be the top-pred row
// for the first row in next iteration.
const int width = transform->xsize_;
memcpy(out - width, out + (row_end - row_start - 1) * width,
width * sizeof(*out));
}
break;
case CROSS_COLOR_TRANSFORM:
ColorSpaceInverseTransform(transform, row_start, row_end, out);
break;
case COLOR_INDEXING_TRANSFORM:
ColorIndexInverseTransform(transform, row_start, row_end, in, out);
break;
}
}
//------------------------------------------------------------------------------
// Color space conversion.
static int is_big_endian(void) {
static const union {
uint16_t w;
uint8_t b[2];
} tmp = { 1 };
return (tmp.b[0] != 1);
}
static void ConvertBGRAToRGB(const uint32_t* src,
int num_pixels, uint8_t* dst) {
const uint32_t* const src_end = src + num_pixels;
while (src < src_end) {
const uint32_t argb = *src++;
*dst++ = (argb >> 16) & 0xff;
*dst++ = (argb >> 8) & 0xff;
*dst++ = (argb >> 0) & 0xff;
}
}
static void ConvertBGRAToRGBA(const uint32_t* src,
int num_pixels, uint8_t* dst) {
const uint32_t* const src_end = src + num_pixels;
while (src < src_end) {
const uint32_t argb = *src++;
*dst++ = (argb >> 16) & 0xff;
*dst++ = (argb >> 8) & 0xff;
*dst++ = (argb >> 0) & 0xff;
*dst++ = (argb >> 24) & 0xff;
}
}
static void ConvertBGRAToRGBA4444(const uint32_t* src,
int num_pixels, uint8_t* dst) {
const uint32_t* const src_end = src + num_pixels;
while (src < src_end) {
const uint32_t argb = *src++;
*dst++ = ((argb >> 16) & 0xf0) | ((argb >> 12) & 0xf);
*dst++ = ((argb >> 0) & 0xf0) | ((argb >> 28) & 0xf);
}
}
static void ConvertBGRAToRGB565(const uint32_t* src,
int num_pixels, uint8_t* dst) {
const uint32_t* const src_end = src + num_pixels;
while (src < src_end) {
const uint32_t argb = *src++;
*dst++ = ((argb >> 16) & 0xf8) | ((argb >> 13) & 0x7);
*dst++ = ((argb >> 5) & 0xe0) | ((argb >> 3) & 0x1f);
}
}
static void ConvertBGRAToBGR(const uint32_t* src,
int num_pixels, uint8_t* dst) {
const uint32_t* const src_end = src + num_pixels;
while (src < src_end) {
const uint32_t argb = *src++;
*dst++ = (argb >> 0) & 0xff;
*dst++ = (argb >> 8) & 0xff;
*dst++ = (argb >> 16) & 0xff;
}
}
static void CopyOrSwap(const uint32_t* src, int num_pixels, uint8_t* dst,
int swap_on_big_endian) {
if (is_big_endian() == swap_on_big_endian) {
const uint32_t* const src_end = src + num_pixels;
while (src < src_end) {
uint32_t argb = *src++;
#if !defined(__BIG_ENDIAN__) && (defined(__i386__) || defined(__x86_64__))
__asm__ volatile("bswap %0" : "=r"(argb) : "0"(argb));
*(uint32_t*)dst = argb;
dst += sizeof(argb);
#elif !defined(__BIG_ENDIAN__) && defined(_MSC_VER)
argb = _byteswap_ulong(argb);
*(uint32_t*)dst = argb;
dst += sizeof(argb);
#else
*dst++ = (argb >> 24) & 0xff;
*dst++ = (argb >> 16) & 0xff;
*dst++ = (argb >> 8) & 0xff;
*dst++ = (argb >> 0) & 0xff;
#endif
}
} else {
memcpy(dst, src, num_pixels * sizeof(*src));
}
}
void VP8LConvertFromBGRA(const uint32_t* const in_data, int num_pixels,
WEBP_CSP_MODE out_colorspace,
uint8_t* const rgba) {
switch (out_colorspace) {
case MODE_RGB:
ConvertBGRAToRGB(in_data, num_pixels, rgba);
break;
case MODE_RGBA:
ConvertBGRAToRGBA(in_data, num_pixels, rgba);
break;
case MODE_BGR:
ConvertBGRAToBGR(in_data, num_pixels, rgba);
break;
case MODE_BGRA:
CopyOrSwap(in_data, num_pixels, rgba, 1);
break;
case MODE_ARGB:
CopyOrSwap(in_data, num_pixels, rgba, 0);
break;
case MODE_RGBA_4444:
ConvertBGRAToRGBA4444(in_data, num_pixels, rgba);
break;
case MODE_RGB_565:
ConvertBGRAToRGB565(in_data, num_pixels, rgba);
break;
default:
assert(0); // Code flow should not reach here.
}
}
//------------------------------------------------------------------------------
#if defined(__cplusplus) || defined(c_plusplus)
} // extern "C"
#endif
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