ShuriZma
/
mgba
mirror of https://github.com/mgba-emu/mgba.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Util: Fix alpha blending calculation

This commit is contained in:
Vicki Pfau 2023-07-23 12:37:59 -07:00
parent c8cfaefcc8
commit 369eab8da3
2 changed files with 88 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

115
include/mgba-util/image.h
View File

@ -271,51 +271,108 @@ ATTRIBUTE_UNUSED static unsigned mColorMix5Bit(int weightA, unsigned colorA, int
}
ATTRIBUTE_UNUSED static uint32_t mColorMixARGB8(uint32_t colorA, uint32_t colorB) {
uint32_t alpha = colorA >> 24;
if (!alpha) {
uint32_t alphaA = colorA >> 24;
if (!alphaA) {
return colorB;
}
uint32_t alphaB = colorB >> 24;
uint32_t color = 0;
#if 1
// TODO: Benchmark integer and float versions
uint32_t a, b;
a = colorA & 0xFF00FF;
a *= alpha + 1;
color += (a >> 8) & 0xFF00FF;
uint32_t alpha = (alphaA * 0xFF) + alphaB * (0xFF - alphaA);
a = colorB & 0xFF00FF;
a *= 0x100 - alpha;
color += (a >> 8) & 0xFF00FF;
a = colorA & 0xFF;
a *= alphaA * 0xFF;
b = a;
if (color & 0x100) {
color &= ~0xFF;
a = colorB & 0xFF;
a *= alphaB * (0xFF - alphaA);
b += a;
b /= alpha;
if (b > 0xFF) {
color |= 0xFF;
} else {
color |= b;
}
if (color & 0x1000000) {
color &= ~0xFF0000;
a = (colorA >> 8) & 0xFF;
a *= alphaA * 0xFF;
b = a;
a = (colorB >> 8) & 0xFF;
a *= alphaB * (0xFF - alphaA);
b += a;
b /= alpha;
if (b > 0xFF) {
color |= 0xFF00;
} else {
color |= b << 8;
}
a = (colorA >> 16) & 0xFF;
a *= alphaA * 0xFF;
b = a;
a = (colorB >> 16) & 0xFF;
a *= alphaB * (0xFF - alphaA);
b += a;
b /= alpha;
if (b > 0xFF) {
color |= 0xFF0000;
} else {
color |= b << 16;
}
b = 0;
a = colorA & 0xFF00;
a *= alpha + 1;
b += a & 0xFF0000;
a = colorB & 0xFF00;
a *= 0x100 - alpha;
b += a & 0xFF0000;
if (b & 0x1000000) {
b &= ~0xFF0000;
b |= 0xFF0000;
}
color |= b >> 8;
alpha += colorB >> 24;
alpha /= 0xFF;
if (alpha > 0xFF) {
color |= 0xFF000000;
} else {
color |= alpha << 24;
}
#else
float ca, aa;
float cb, ab;
static const float r255 = 1 / 255.f;
aa = alphaA * r255;
ab = alphaB * r255;
float alpha = aa + ab * (1.f - aa);
float ralpha = 1.f / alpha;
alpha = alpha * 255.f;
color = ((int) alpha) << 24;
ca = ((colorA >> 16) & 0xFF) * r255;
cb = ((colorB >> 16) & 0xFF) * r255;
ca = ca * aa + cb * ab * (1.f - aa);
ca = ca * ralpha * 255.f;
if (ca > 255.f) {
ca = 255.f;
}
color |= ((int) ca) << 16;
ca = ((colorA >> 8) & 0xFF) * r255;
cb = ((colorB >> 8) & 0xFF) * r255;
ca = ca * aa + cb * ab * (1.f - aa);
ca = ca * ralpha * 255.f;
if (ca > 255.f) {
ca = 255.f;
}
color |= ((int) ca) << 8;
ca = (colorA & 0xFF) * r255;
cb = (colorB & 0xFF) * r255;
ca = ca * aa + cb * ab * (1.f - aa);
ca = ca * ralpha * 255.f;
if (ca > 255.f) {
ca = 255.f;
}
color |= (int) ca;
#endif
return color;
}

4
src/util/test/color.c
View File

@ -155,9 +155,9 @@ M_TEST_DEFINE(alphaBlendARGB8) {
assert_int_equal(mColorMixARGB8(0xFF012345, 0xFF987654), 0xFF012345);
assert_int_equal(mColorMixARGB8(0x00012345, 0xFF987654), 0xFF987654);
assert_int_equal(mColorMixARGB8(0x80012345, 0xFF987654), 0xFF4C4C4C);
assert_int_equal(mColorMixARGB8(0x80012345, 0x40987654), 0xC04C4C4C);
assert_int_equal(mColorMixARGB8(0x80012345, 0x40987654), 0x9F1F3347);
assert_int_equal(mColorMixARGB8(0x01012345, 0xFF987654), 0xFF977553);
assert_int_equal(mColorMixARGB8(0x01012345, 0xFD987654), 0xFE977553);
assert_int_equal(mColorMixARGB8(0x01012345, 0xFD987654), 0xFD977553);
}
M_TEST_SUITE_DEFINE(Color,