// 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 <array>
#include "lib/jxl/base/common.h"
#include "lib/jxl/testing.h"
namespace jxl {
namespace {
AlphaBlendingInputLayer makeAbil(
const Color& rgb,
const float& a) {
const float* data = rgb.data();
return {data, data + 1, data + 2, &a};
}
AlphaBlendingOutput makeAbo(Color& rgb,
float& a) {
float* data = rgb.data();
return {data, data + 1, data + 2, &a};
}
TEST(AlphaTest, BlendingWithNonPremultiplied) {
const Color bg_rgb{100, 110, 120};
const float bg_a = 180.f / 255;
const Color fg_rgb{25, 21, 23};
const float fg_a = 15420.f / 65535;
const float fg_a2 = 2.0f;
Color out_rgb;
float out_a;
PerformAlphaBlending(
/*bg=*/makeAbil(bg_rgb, bg_a),
/*fg=*/makeAbil(fg_rgb, fg_a),
/*out=*/makeAbo(out_rgb, out_a), 1,
/*alpha_is_premultiplied=*/false, /*clamp=*/false);
EXPECT_ARRAY_NEAR(out_rgb, (Color{77.2f, 83.0f, 90.6f}), 0.05f);
EXPECT_NEAR(out_a, 3174.f / 4095, 1e-5);
PerformAlphaBlending(
/*bg=*/makeAbil(bg_rgb, bg_a),
/*fg=*/makeAbil(fg_rgb, fg_a2),
/*out=*/makeAbo(out_rgb, out_a), 1,
/*alpha_is_premultiplied=*/false, /*clamp=*/true);
EXPECT_ARRAY_NEAR(out_rgb, fg_rgb, 0.05f);
EXPECT_NEAR(out_a, 1.0f, 1e-5);
}
TEST(AlphaTest, BlendingWithPremultiplied) {
const Color bg_rgb{100, 110, 120};
const float bg_a = 180.f / 255;
const Color fg_rgb{25, 21, 23};
const float fg_a = 15420.f / 65535;
const float fg_a2 = 2.0f;
Color out_rgb;
float out_a;
PerformAlphaBlending(
/*bg=*/makeAbil(bg_rgb, bg_a),
/*fg=*/makeAbil(fg_rgb, fg_a),
/*out=*/makeAbo(out_rgb, out_a), 1,
/*alpha_is_premultiplied=*/true, /*clamp=*/false);
EXPECT_ARRAY_NEAR(out_rgb, (Color{101.5f, 105.1f, 114.8f}), 0.05f);
EXPECT_NEAR(out_a, 3174.f / 4095, 1e-5);
PerformAlphaBlending(
/*bg=*/makeAbil(bg_rgb, bg_a),
/*fg=*/makeAbil(fg_rgb, fg_a2),
/*out=*/makeAbo(out_rgb, out_a), 1,
/*alpha_is_premultiplied=*/true, /*clamp=*/true);
EXPECT_ARRAY_NEAR(out_rgb, fg_rgb, 0.05f);
EXPECT_NEAR(out_a, 1.0f, 1e-5);
}
TEST(AlphaTest, Mul) {
const float bg = 100;
const float fg = 25;
float out;
PerformMulBlending(&bg, &fg, &out, 1,
/*clamp=*/false);
EXPECT_NEAR(out, fg * bg, .05f);
PerformMulBlending(&bg, &fg, &out, 1,
/*clamp=*/true);
EXPECT_NEAR(out, bg, .05f);
}
TEST(AlphaTest, PremultiplyAndUnpremultiply) {
using F4 = std::array<
float, 4>;
const F4 alpha{0.f, 63.f / 255, 127.f / 255, 1.f};
F4 r{120, 130, 140, 150};
F4 g{124, 134, 144, 154};
F4 b{127, 137, 147, 157};
PremultiplyAlpha(r.data(), g.data(), b.data(), alpha.data(), alpha.size());
EXPECT_ARRAY_NEAR(r, (F4{0.0f, 130 * 63.f / 255, 140 * 127.f / 255, 150}),
1e-5f);
EXPECT_ARRAY_NEAR(g, (F4{0.0f, 134 * 63.f / 255, 144 * 127.f / 255, 154}),
1e-5f);
EXPECT_ARRAY_NEAR(b, (F4{0.0f, 137 * 63.f / 255, 147 * 127.f / 255, 157}),
1e-5f);
UnpremultiplyAlpha(r.data(), g.data(), b.data(), alpha.data(), alpha.size());
EXPECT_ARRAY_NEAR(r, (F4{120, 130, 140, 150}), 1e-4f);
EXPECT_ARRAY_NEAR(g, (F4{124, 134, 144, 154}), 1e-4f);
EXPECT_ARRAY_NEAR(b, (F4{127, 137, 147, 157}), 1e-4f);
}
TEST(AlphaTest, UnpremultiplyAndPremultiply) {
using F4 = std::array<
float, 4>;
const F4 alpha{0.f, 63.f / 255, 127.f / 255, 1.f};
F4 r{50, 60, 70, 80};
F4 g{54, 64, 74, 84};
F4 b{57, 67, 77, 87};
UnpremultiplyAlpha(r.data(), g.data(), b.data(), alpha.data(), alpha.size());
EXPECT_ARRAY_NEAR(
r, (F4{50.0f * (1 << 26), 60 * 255.f / 63, 70 * 255.f / 127, 80}), 1e-4f);
EXPECT_ARRAY_NEAR(
g, (F4{54.0f * (1 << 26), 64 * 255.f / 63, 74 * 255.f / 127, 84}), 1e-4f);
EXPECT_ARRAY_NEAR(
b, (F4{57.0f * (1 << 26), 67 * 255.f / 63, 77 * 255.f / 127, 87}), 1e-4f);
PremultiplyAlpha(r.data(), g.data(), b.data(), alpha.data(), alpha.size());
EXPECT_ARRAY_NEAR(r, (F4{50, 60, 70, 80}), 1e-4);
EXPECT_ARRAY_NEAR(g, (F4{54, 64, 74, 84}), 1e-4);
EXPECT_ARRAY_NEAR(b, (F4{57, 67, 77, 87}), 1e-4);
}
}
// namespace
}
// namespace jxl
