SameBoy/Shaders/AAOmniScaleLegacy.fsh
LMLB 0c80ac3296 Fix shaders that sample at texel edges
Sampling at the edge between texels causes one or the other to be chosen
semi-randomly, depending on rounding errors. Add half a pixel so they
sample at texel centers instead.
2018-03-14 20:05:51 +01:00

119 lines
3.5 KiB
GLSL

float quickDistance(vec4 a, vec4 b)
{
return abs(a.x - b.x) + abs(a.y - b.y) + abs(a.z - b.z);
}
vec4 omniScale(sampler2D image, vec2 texCoord)
{
vec2 pixel = texCoord * textureDimensions - vec2(0.5, 0.5);
vec4 q11 = texture(image, (floor(pixel) + 0.5) / textureDimensions);
vec4 q12 = texture(image, (vec2(floor(pixel.x), ceil(pixel.y)) + 0.5) / textureDimensions);
vec4 q21 = texture(image, (vec2(ceil(pixel.x), floor(pixel.y)) + 0.5) / textureDimensions);
vec4 q22 = texture(image, (ceil(pixel) + 0.5) / textureDimensions);
vec2 pos = fract(pixel);
/* Special handling for diaonals */
bool hasDownDiagonal = false;
bool hasUpDiagonal = false;
if (q12 == q21 && q11 != q22) hasUpDiagonal = true;
else if (q12 != q21 && q11 == q22) hasDownDiagonal = true;
else if (q12 == q21 && q11 == q22) {
if (q11 == q12) return q11;
int diagonalBias = 0;
for (float y = -1.0; y < 3.0; y++) {
for (float x = -1.0; x < 3.0; x++) {
vec4 color = texture(image, (pixel + vec2(x, y)) / textureDimensions);
if (color == q11) diagonalBias++;
if (color == q12) diagonalBias--;
}
}
if (diagonalBias <= 0) {
hasDownDiagonal = true;
}
if (diagonalBias >= 0) {
hasUpDiagonal = true;
}
}
if (hasUpDiagonal || hasDownDiagonal) {
vec4 downDiagonalResult, upDiagonalResult;
if (hasUpDiagonal) {
float diagonalPos = pos.x + pos.y;
if (diagonalPos < 0.5) {
upDiagonalResult = q11;
}
else if (diagonalPos > 1.5) {
upDiagonalResult = q22;
}
else {
upDiagonalResult = q12;
}
}
if (hasDownDiagonal) {
float diagonalPos = 1.0 - pos.x + pos.y;
if (diagonalPos < 0.5) {
downDiagonalResult = q21;
}
else if (diagonalPos > 1.5) {
downDiagonalResult = q12;
}
else {
downDiagonalResult = q11;
}
}
if (!hasUpDiagonal) return downDiagonalResult;
if (!hasDownDiagonal) return upDiagonalResult;
return mix(downDiagonalResult, upDiagonalResult, 0.5);
}
vec4 r1 = mix(q11, q21, fract(pos.x));
vec4 r2 = mix(q12, q22, fract(pos.x));
vec4 unqunatized = mix(r1, r2, fract(pos.y));
float q11d = quickDistance(unqunatized, q11);
float q21d = quickDistance(unqunatized, q21);
float q12d = quickDistance(unqunatized, q12);
float q22d = quickDistance(unqunatized, q22);
float best = min(q11d,
min(q21d,
min(q12d,
q22d)));
if (q11d == best) {
return q11;
}
if (q21d == best) {
return q21;
}
if (q12d == best) {
return q12;
}
return q22;
}
vec4 scale(sampler2D image)
{
vec2 texCoord = vec2(gl_FragCoord.x, uResolution.y - gl_FragCoord.y) / uResolution;
vec2 pixel = vec2(1.0, 1.0) / uResolution;
// 4-pixel super sampling
vec4 q11 = omniScale(image, texCoord + pixel * vec2(-0.25, -0.25));
vec4 q21 = omniScale(image, texCoord + pixel * vec2(+0.25, -0.25));
vec4 q12 = omniScale(image, texCoord + pixel * vec2(-0.25, +0.25));
vec4 q22 = omniScale(image, texCoord + pixel * vec2(+0.25, +0.25));
return (q11 + q21 + q12 + q22) / 4.0;
}