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libwebp/sharpyuv/sharpyuv.c
Maryla 7a68afaac5 Let SharpArgbToYuv caller pass in an RGB>YUV conversion matrix. 
Change-Id: I4ed2dfc00ce63361abd49c693f31f307e0b0262f
2022-03-24 16:37:47 +01:00

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// Copyright 2022 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.
// -----------------------------------------------------------------------------
//
// Sharp RGB to YUV conversion.
//
// Author: Skal (pascal.massimino@gmail.com)
#include "./sharpyuv.h"
#include <assert.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
#include "src/webp/types.h"
#include "src/dsp/cpu.h"
#include "sharpyuv/sharpyuv_dsp.h"
//------------------------------------------------------------------------------
// Code for gamma correction
// gamma-compensates loss of resolution during chroma subsampling
#define kGamma 0.80 // for now we use a different gamma value than kGammaF
#define kGammaFix 12 // fixed-point precision for linear values
#define kGammaScale ((1 << kGammaFix) - 1)
#define kGammaTabFix 7 // fixed-point fractional bits precision
#define kGammaTabScale (1 << kGammaTabFix)
#define kGammaTabRounder (kGammaTabScale >> 1)
#define kGammaTabSize (1 << (kGammaFix - kGammaTabFix))
enum {
YUV_FIX = 16, // fixed-point precision for RGB->YUV
YUV_HALF = 1 << (YUV_FIX - 1),
};
//------------------------------------------------------------------------------
// Sharp RGB->YUV conversion
static const int kNumIterations = 4;
static const int kMinDimensionIterativeConversion = 4;
// We could use SFIX=0 and only uint8_t for fixed_y_t, but it produces some
// banding sometimes. Better use extra precision.
#define SFIX 2 // fixed-point precision of RGB and Y/W
typedef int16_t fixed_t; // signed type with extra SFIX precision for UV
typedef uint16_t fixed_y_t; // unsigned type with extra SFIX precision for W
#define SHALF (1 << SFIX >> 1)
#define MAX_Y_T ((256 << SFIX) - 1)
#define SROUNDER (1 << (YUV_FIX + SFIX - 1))
// We use tables of different size and precision for the Rec709 / BT2020
// transfer function.
#define kGammaF (1./0.45)
static uint32_t kLinearToGammaTabS[kGammaTabSize + 2];
#define GAMMA_TO_LINEAR_BITS 14
static uint32_t kGammaToLinearTabS[MAX_Y_T + 1]; // size scales with Y_FIX
static volatile int kGammaTablesSOk = 0;
static void InitGammaTablesS(void);
WEBP_DSP_INIT_FUNC(InitGammaTablesS) {
assert(2 * GAMMA_TO_LINEAR_BITS < 32); // we use uint32_t intermediate values
if (!kGammaTablesSOk) {
int v;
const double norm = 1. / MAX_Y_T;
const double scale = 1. / kGammaTabSize;
const double a = 0.09929682680944;
const double thresh = 0.018053968510807;
const double final_scale = 1 << GAMMA_TO_LINEAR_BITS;
for (v = 0; v <= MAX_Y_T; ++v) {
const double g = norm * v;
double value;
if (g <= thresh * 4.5) {
value = g / 4.5;
} else {
const double a_rec = 1. / (1. + a);
value = pow(a_rec * (g + a), kGammaF);
}
kGammaToLinearTabS[v] = (uint32_t)(value * final_scale + .5);
}
for (v = 0; v <= kGammaTabSize; ++v) {
const double g = scale * v;
double value;
if (g <= thresh) {
value = 4.5 * g;
} else {
value = (1. + a) * pow(g, 1. / kGammaF) - a;
}
// we already incorporate the 1/2 rounding constant here
kLinearToGammaTabS[v] =
(uint32_t)(MAX_Y_T * value) + (1 << GAMMA_TO_LINEAR_BITS >> 1);
}
// to prevent small rounding errors to cause read-overflow:
kLinearToGammaTabS[kGammaTabSize + 1] = kLinearToGammaTabS[kGammaTabSize];
kGammaTablesSOk = 1;
}
}
// return value has a fixed-point precision of GAMMA_TO_LINEAR_BITS
static WEBP_INLINE uint32_t GammaToLinearS(int v) {
return kGammaToLinearTabS[v];
}
static WEBP_INLINE uint32_t LinearToGammaS(uint32_t value) {
// 'value' is in GAMMA_TO_LINEAR_BITS fractional precision
const uint32_t v = value * kGammaTabSize;
const uint32_t tab_pos = v >> GAMMA_TO_LINEAR_BITS;
// fractional part, in GAMMA_TO_LINEAR_BITS fixed-point precision
const uint32_t x = v - (tab_pos << GAMMA_TO_LINEAR_BITS); // fractional part
// v0 / v1 are in GAMMA_TO_LINEAR_BITS fixed-point precision (range [0..1])
const uint32_t v0 = kLinearToGammaTabS[tab_pos + 0];
const uint32_t v1 = kLinearToGammaTabS[tab_pos + 1];
// Final interpolation. Note that rounding is already included.
const uint32_t v2 = (v1 - v0) * x; // note: v1 >= v0.
const uint32_t result = v0 + (v2 >> GAMMA_TO_LINEAR_BITS);
return result;
}
//------------------------------------------------------------------------------
static uint8_t clip_8b(fixed_t v) {
return (!(v & ~0xff)) ? (uint8_t)v : (v < 0) ? 0u : 255u;
}
static fixed_y_t clip_y(int y) {
return (!(y & ~MAX_Y_T)) ? (fixed_y_t)y : (y < 0) ? 0 : MAX_Y_T;
}
//------------------------------------------------------------------------------
static int RGBToGray(int r, int g, int b) {
const int luma = 13933 * r + 46871 * g + 4732 * b + YUV_HALF;
return (luma >> YUV_FIX);
}
static uint32_t ScaleDown(int a, int b, int c, int d) {
const uint32_t A = GammaToLinearS(a);
const uint32_t B = GammaToLinearS(b);
const uint32_t C = GammaToLinearS(c);
const uint32_t D = GammaToLinearS(d);
return LinearToGammaS((A + B + C + D + 2) >> 2);
}
static WEBP_INLINE void UpdateW(const fixed_y_t* src, fixed_y_t* dst, int w) {
int i;
for (i = 0; i < w; ++i) {
const uint32_t R = GammaToLinearS(src[0 * w + i]);
const uint32_t G = GammaToLinearS(src[1 * w + i]);
const uint32_t B = GammaToLinearS(src[2 * w + i]);
const uint32_t Y = RGBToGray(R, G, B);
dst[i] = (fixed_y_t)LinearToGammaS(Y);
}
}
static void UpdateChroma(const fixed_y_t* src1, const fixed_y_t* src2,
fixed_t* dst, int uv_w) {
int i;
for (i = 0; i < uv_w; ++i) {
const int r = ScaleDown(src1[0 * uv_w + 0], src1[0 * uv_w + 1],
src2[0 * uv_w + 0], src2[0 * uv_w + 1]);
const int g = ScaleDown(src1[2 * uv_w + 0], src1[2 * uv_w + 1],
src2[2 * uv_w + 0], src2[2 * uv_w + 1]);
const int b = ScaleDown(src1[4 * uv_w + 0], src1[4 * uv_w + 1],
src2[4 * uv_w + 0], src2[4 * uv_w + 1]);
const int W = RGBToGray(r, g, b);
dst[0 * uv_w] = (fixed_t)(r - W);
dst[1 * uv_w] = (fixed_t)(g - W);
dst[2 * uv_w] = (fixed_t)(b - W);
dst += 1;
src1 += 2;
src2 += 2;
}
}
static void StoreGray(const fixed_y_t* rgb, fixed_y_t* y, int w) {
int i;
for (i = 0; i < w; ++i) {
y[i] = RGBToGray(rgb[0 * w + i], rgb[1 * w + i], rgb[2 * w + i]);
}
}
//------------------------------------------------------------------------------
static WEBP_INLINE fixed_y_t Filter2(int A, int B, int W0) {
const int v0 = (A * 3 + B + 2) >> 2;
return clip_y(v0 + W0);
}
//------------------------------------------------------------------------------
static WEBP_INLINE fixed_y_t UpLift(uint8_t a) { // 8bit -> SFIX
return ((fixed_y_t)a << SFIX) | SHALF;
}
static void ImportOneRow(const uint8_t* const r_ptr,
const uint8_t* const g_ptr,
const uint8_t* const b_ptr,
int step,
int pic_width,
fixed_y_t* const dst) {
int i;
const int w = (pic_width + 1) & ~1;
for (i = 0; i < pic_width; ++i) {
const int off = i * step;
dst[i + 0 * w] = UpLift(r_ptr[off]);
dst[i + 1 * w] = UpLift(g_ptr[off]);
dst[i + 2 * w] = UpLift(b_ptr[off]);
}
if (pic_width & 1) { // replicate rightmost pixel
dst[pic_width + 0 * w] = dst[pic_width + 0 * w - 1];
dst[pic_width + 1 * w] = dst[pic_width + 1 * w - 1];
dst[pic_width + 2 * w] = dst[pic_width + 2 * w - 1];
}
}
static void InterpolateTwoRows(const fixed_y_t* const best_y,
const fixed_t* prev_uv,
const fixed_t* cur_uv,
const fixed_t* next_uv,
int w,
fixed_y_t* out1,
fixed_y_t* out2) {
const int uv_w = w >> 1;
const int len = (w - 1) >> 1; // length to filter
int k = 3;
while (k-- > 0) { // process each R/G/B segments in turn
// special boundary case for i==0
out1[0] = Filter2(cur_uv[0], prev_uv[0], best_y[0]);
out2[0] = Filter2(cur_uv[0], next_uv[0], best_y[w]);
SharpYUVFilterRow(cur_uv, prev_uv, len, best_y + 0 + 1, out1 + 1);
SharpYUVFilterRow(cur_uv, next_uv, len, best_y + w + 1, out2 + 1);
// special boundary case for i == w - 1 when w is even
if (!(w & 1)) {
out1[w - 1] = Filter2(cur_uv[uv_w - 1], prev_uv[uv_w - 1],
best_y[w - 1 + 0]);
out2[w - 1] = Filter2(cur_uv[uv_w - 1], next_uv[uv_w - 1],
best_y[w - 1 + w]);
}
out1 += w;
out2 += w;
prev_uv += uv_w;
cur_uv += uv_w;
next_uv += uv_w;
}
}
static WEBP_INLINE uint8_t RGBToYUVComponent(int r, int g, int b,
const int coeffs[4]) {
const int luma = coeffs[0] * r + coeffs[1] * g + coeffs[2] * b +
(coeffs[3] << SFIX) + SROUNDER;
return clip_8b((luma >> (YUV_FIX + SFIX)));
}
static int ConvertWRGBToYUV(const fixed_y_t* best_y, const fixed_t* best_uv,
uint8_t* dst_y, int dst_stride_y, uint8_t* dst_u,
int dst_stride_u, uint8_t* dst_v, int dst_stride_v,
int width, int height,
const SharpYuvConversionMatrix* yuv_matrix) {
int i, j;
const fixed_t* const best_uv_base = best_uv;
const int w = (width + 1) & ~1;
const int h = (height + 1) & ~1;
const int uv_w = w >> 1;
const int uv_h = h >> 1;
for (best_uv = best_uv_base, j = 0; j < height; ++j) {
for (i = 0; i < width; ++i) {
const int off = (i >> 1);
const int W = best_y[i];
const int r = best_uv[off + 0 * uv_w] + W;
const int g = best_uv[off + 1 * uv_w] + W;
const int b = best_uv[off + 2 * uv_w] + W;
dst_y[i] = RGBToYUVComponent(r, g, b, yuv_matrix->rgb_to_y);
}
best_y += w;
best_uv += (j & 1) * 3 * uv_w;
dst_y += dst_stride_y;
}
for (best_uv = best_uv_base, j = 0; j < uv_h; ++j) {
for (i = 0; i < uv_w; ++i) {
const int off = i;
const int r = best_uv[off + 0 * uv_w];
const int g = best_uv[off + 1 * uv_w];
const int b = best_uv[off + 2 * uv_w];
dst_u[i] = RGBToYUVComponent(r, g, b, yuv_matrix->rgb_to_u);
dst_v[i] = RGBToYUVComponent(r, g, b, yuv_matrix->rgb_to_v);
}
best_uv += 3 * uv_w;
dst_u += dst_stride_u;
dst_v += dst_stride_v;
}
return 1;
}
//------------------------------------------------------------------------------
// Main function
static void* SafeMalloc(uint64_t nmemb, size_t size) {
const uint64_t total_size = nmemb * (uint64_t)size;
if (total_size != (size_t)total_size) return NULL;
return malloc((size_t)total_size);
}
#define SAFE_ALLOC(W, H, T) ((T*)SafeMalloc((W) * (H), sizeof(T)))
static int DoSharpArgbToYuv(const uint8_t* r_ptr, const uint8_t* g_ptr,
const uint8_t* b_ptr, int step, int rgb_stride,
uint8_t* dst_y, int dst_stride_y, uint8_t* dst_u,
int dst_stride_u, uint8_t* dst_v, int dst_stride_v,
int width, int height,
const SharpYuvConversionMatrix* yuv_matrix) {
// we expand the right/bottom border if needed
const int w = (width + 1) & ~1;
const int h = (height + 1) & ~1;
const int uv_w = w >> 1;
const int uv_h = h >> 1;
uint64_t prev_diff_y_sum = ~0;
int j, iter;
// TODO(skal): allocate one big memory chunk. But for now, it's easier
// for valgrind debugging to have several chunks.
fixed_y_t* const tmp_buffer = SAFE_ALLOC(w * 3, 2, fixed_y_t); // scratch
fixed_y_t* const best_y_base = SAFE_ALLOC(w, h, fixed_y_t);
fixed_y_t* const target_y_base = SAFE_ALLOC(w, h, fixed_y_t);
fixed_y_t* const best_rgb_y = SAFE_ALLOC(w, 2, fixed_y_t);
fixed_t* const best_uv_base = SAFE_ALLOC(uv_w * 3, uv_h, fixed_t);
fixed_t* const target_uv_base = SAFE_ALLOC(uv_w * 3, uv_h, fixed_t);
fixed_t* const best_rgb_uv = SAFE_ALLOC(uv_w * 3, 1, fixed_t);
fixed_y_t* best_y = best_y_base;
fixed_y_t* target_y = target_y_base;
fixed_t* best_uv = best_uv_base;
fixed_t* target_uv = target_uv_base;
const uint64_t diff_y_threshold = (uint64_t)(3.0 * w * h);
int ok;
if (best_y_base == NULL || best_uv_base == NULL ||
target_y_base == NULL || target_uv_base == NULL ||
best_rgb_y == NULL || best_rgb_uv == NULL ||
tmp_buffer == NULL) {
ok = 0;
goto End;
}
InitGammaTablesS();
InitSharpYuv();
// Import RGB samples to W/RGB representation.
for (j = 0; j < height; j += 2) {
const int is_last_row = (j == height - 1);
fixed_y_t* const src1 = tmp_buffer + 0 * w;
fixed_y_t* const src2 = tmp_buffer + 3 * w;
// prepare two rows of input
ImportOneRow(r_ptr, g_ptr, b_ptr, step, width, src1);
if (!is_last_row) {
ImportOneRow(r_ptr + rgb_stride, g_ptr + rgb_stride, b_ptr + rgb_stride,
step, width, src2);
} else {
memcpy(src2, src1, 3 * w * sizeof(*src2));
}
StoreGray(src1, best_y + 0, w);
StoreGray(src2, best_y + w, w);
UpdateW(src1, target_y, w);
UpdateW(src2, target_y + w, w);
UpdateChroma(src1, src2, target_uv, uv_w);
memcpy(best_uv, target_uv, 3 * uv_w * sizeof(*best_uv));
best_y += 2 * w;
best_uv += 3 * uv_w;
target_y += 2 * w;
target_uv += 3 * uv_w;
r_ptr += 2 * rgb_stride;
g_ptr += 2 * rgb_stride;
b_ptr += 2 * rgb_stride;
}
// Iterate and resolve clipping conflicts.
for (iter = 0; iter < kNumIterations; ++iter) {
const fixed_t* cur_uv = best_uv_base;
const fixed_t* prev_uv = best_uv_base;
uint64_t diff_y_sum = 0;
best_y = best_y_base;
best_uv = best_uv_base;
target_y = target_y_base;
target_uv = target_uv_base;
for (j = 0; j < h; j += 2) {
fixed_y_t* const src1 = tmp_buffer + 0 * w;
fixed_y_t* const src2 = tmp_buffer + 3 * w;
{
const fixed_t* const next_uv = cur_uv + ((j < h - 2) ? 3 * uv_w : 0);
InterpolateTwoRows(best_y, prev_uv, cur_uv, next_uv, w, src1, src2);
prev_uv = cur_uv;
cur_uv = next_uv;
}
UpdateW(src1, best_rgb_y + 0 * w, w);
UpdateW(src2, best_rgb_y + 1 * w, w);
UpdateChroma(src1, src2, best_rgb_uv, uv_w);
// update two rows of Y and one row of RGB
diff_y_sum += SharpYUVUpdateY(target_y, best_rgb_y, best_y, 2 * w);
SharpYUVUpdateRGB(target_uv, best_rgb_uv, best_uv, 3 * uv_w);
best_y += 2 * w;
best_uv += 3 * uv_w;
target_y += 2 * w;
target_uv += 3 * uv_w;
}
// test exit condition
if (iter > 0) {
if (diff_y_sum < diff_y_threshold) break;
if (diff_y_sum > prev_diff_y_sum) break;
}
prev_diff_y_sum = diff_y_sum;
}
// final reconstruction
ok = ConvertWRGBToYUV(best_y_base, best_uv_base, dst_y, dst_stride_y, dst_u,
dst_stride_u, dst_v, dst_stride_v, width, height,
yuv_matrix);
End:
free(best_y_base);
free(best_uv_base);
free(target_y_base);
free(target_uv_base);
free(best_rgb_y);
free(best_rgb_uv);
free(tmp_buffer);
return ok;
}
#undef SAFE_ALLOC
// In YUV_FIX fixed point precision.
static const SharpYuvConversionMatrix kWebpYuvMatrix = {
{16839, 33059, 6420, 16 << 16},
{-9719, -19081, 28800, 128 << 16},
{28800, -24116, -4684, 128 << 16},
};
const SharpYuvConversionMatrix* SharpYuvGetWebpMatrix(void) {
return &kWebpYuvMatrix;
}
int SharpYuvConvert(const uint8_t* r_ptr, const uint8_t* g_ptr,
const uint8_t* b_ptr, int step, int rgb_stride,
uint8_t* dst_y, int dst_stride_y, uint8_t* dst_u,
int dst_stride_u, uint8_t* dst_v, int dst_stride_v,
int width, int height,
const SharpYuvConversionMatrix* yuv_matrix) {
if (width < kMinDimensionIterativeConversion ||
height < kMinDimensionIterativeConversion) {
return 0;
}
return DoSharpArgbToYuv(r_ptr, g_ptr, b_ptr, step, rgb_stride, dst_y,
dst_stride_y, dst_u, dst_stride_u, dst_v,
dst_stride_v, width, height, yuv_matrix);
}
//------------------------------------------------------------------------------
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