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// Copyright (c) the JPEG XL Project Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#include "lib/jxl/alpha.h"
#include <string.h>
#include <algorithm>
namespace jxl {
static float Clamp(float x) { return std::max(std::min(1.0f, x), 0.0f); }
void PerformAlphaBlending(const AlphaBlendingInputLayer& bg,
const AlphaBlendingInputLayer& fg,
const AlphaBlendingOutput& out, size_t num_pixels,
bool alpha_is_premultiplied, bool clamp) {
if (alpha_is_premultiplied) {
for (size_t x = 0; x < num_pixels; ++x) {
float fga = clamp ? Clamp(fg.a[x]) : fg.a[x];
out.r[x] = (fg.r[x] + bg.r[x] * (1.f - fga));
out.g[x] = (fg.g[x] + bg.g[x] * (1.f - fga));
out.b[x] = (fg.b[x] + bg.b[x] * (1.f - fga));
out.a[x] = (1.f - (1.f - fga) * (1.f - bg.a[x]));
}
} else {
for (size_t x = 0; x < num_pixels; ++x) {
float fga = clamp ? Clamp(fg.a[x]) : fg.a[x];
const float new_a = 1.f - (1.f - fga) * (1.f - bg.a[x]);
const float rnew_a = (new_a > 0 ? 1.f / new_a : 0.f);
out.r[x] = (fg.r[x] * fga + bg.r[x] * bg.a[x] * (1.f - fga)) * rnew_a;
out.g[x] = (fg.g[x] * fga + bg.g[x] * bg.a[x] * (1.f - fga)) * rnew_a;
out.b[x] = (fg.b[x] * fga + bg.b[x] * bg.a[x] * (1.f - fga)) * rnew_a;
out.a[x] = new_a;
}
}
}
void PerformAlphaBlending(const float* bg, const float* bga, const float* fg,
const float* fga, float* out, size_t num_pixels,
bool alpha_is_premultiplied, bool clamp) {
if (bg == bga && fg == fga) {
for (size_t x = 0; x < num_pixels; ++x) {
float fa = clamp ? fga[x] : Clamp(fga[x]);
out[x] = (1.f - (1.f - fa) * (1.f - bga[x]));
}
} else {
if (alpha_is_premultiplied) {
for (size_t x = 0; x < num_pixels; ++x) {
float fa = clamp ? fga[x] : Clamp(fga[x]);
out[x] = (fg[x] + bg[x] * (1.f - fa));
}
} else {
for (size_t x = 0; x < num_pixels; ++x) {
float fa = clamp ? fga[x] : Clamp(fga[x]);
const float new_a = 1.f - (1.f - fa) * (1.f - bga[x]);
const float rnew_a = (new_a > 0 ? 1.f / new_a : 0.f);
out[x] = (fg[x] * fa + bg[x] * bga[x] * (1.f - fa)) * rnew_a;
}
}
}
}
void PerformAlphaWeightedAdd(const float* bg, const float* fg, const float* fga,
float* out, size_t num_pixels, bool clamp) {
if (fg == fga) {
memcpy(out, bg, num_pixels * sizeof(*out));
} else if (clamp) {
for (size_t x = 0; x < num_pixels; ++x) {
out[x] = bg[x] + fg[x] * Clamp(fga[x]);
}
} else {
for (size_t x = 0; x < num_pixels; ++x) {
out[x] = bg[x] + fg[x] * fga[x];
}
}
}
void PerformMulBlending(const float* bg, const float* fg, float* out,
size_t num_pixels, bool clamp) {
if (clamp) {
for (size_t x = 0; x < num_pixels; ++x) {
out[x] = bg[x] * Clamp(fg[x]);
}
} else {
for (size_t x = 0; x < num_pixels; ++x) {
out[x] = bg[x] * fg[x];
}
}
}
void PremultiplyAlpha(float* JXL_RESTRICT r, float* JXL_RESTRICT g,
float* JXL_RESTRICT b, const float* JXL_RESTRICT a,
size_t num_pixels) {
for (size_t x = 0; x < num_pixels; ++x) {
const float multiplier = std::max(kSmallAlpha, a[x]);
r[x] *= multiplier;
g[x] *= multiplier;
b[x] *= multiplier;
}
}
void UnpremultiplyAlpha(float* JXL_RESTRICT r, float* JXL_RESTRICT g,
float* JXL_RESTRICT b, const float* JXL_RESTRICT a,
size_t num_pixels) {
for (size_t x = 0; x < num_pixels; ++x) {
const float multiplier = 1.f / std::max(kSmallAlpha, a[x]);
r[x] *= multiplier;
g[x] *= multiplier;
b[x] *= multiplier;
}
}
} // namespace jxl