0c80ac3296
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.
119 lines
3.5 KiB
GLSL
119 lines
3.5 KiB
GLSL
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float quickDistance(vec4 a, vec4 b)
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{
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return abs(a.x - b.x) + abs(a.y - b.y) + abs(a.z - b.z);
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}
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vec4 omniScale(sampler2D image, vec2 texCoord)
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{
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vec2 pixel = texCoord * textureDimensions - vec2(0.5, 0.5);
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vec4 q11 = texture(image, (floor(pixel) + 0.5) / textureDimensions);
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vec4 q12 = texture(image, (vec2(floor(pixel.x), ceil(pixel.y)) + 0.5) / textureDimensions);
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vec4 q21 = texture(image, (vec2(ceil(pixel.x), floor(pixel.y)) + 0.5) / textureDimensions);
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vec4 q22 = texture(image, (ceil(pixel) + 0.5) / textureDimensions);
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vec2 pos = fract(pixel);
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/* Special handling for diaonals */
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bool hasDownDiagonal = false;
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bool hasUpDiagonal = false;
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if (q12 == q21 && q11 != q22) hasUpDiagonal = true;
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else if (q12 != q21 && q11 == q22) hasDownDiagonal = true;
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else if (q12 == q21 && q11 == q22) {
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if (q11 == q12) return q11;
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int diagonalBias = 0;
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for (float y = -1.0; y < 3.0; y++) {
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for (float x = -1.0; x < 3.0; x++) {
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vec4 color = texture(image, (pixel + vec2(x, y)) / textureDimensions);
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if (color == q11) diagonalBias++;
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if (color == q12) diagonalBias--;
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}
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}
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if (diagonalBias <= 0) {
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hasDownDiagonal = true;
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}
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if (diagonalBias >= 0) {
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hasUpDiagonal = true;
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}
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}
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if (hasUpDiagonal || hasDownDiagonal) {
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vec4 downDiagonalResult, upDiagonalResult;
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if (hasUpDiagonal) {
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float diagonalPos = pos.x + pos.y;
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if (diagonalPos < 0.5) {
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upDiagonalResult = q11;
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}
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else if (diagonalPos > 1.5) {
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upDiagonalResult = q22;
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}
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else {
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upDiagonalResult = q12;
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}
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}
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if (hasDownDiagonal) {
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float diagonalPos = 1.0 - pos.x + pos.y;
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if (diagonalPos < 0.5) {
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downDiagonalResult = q21;
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}
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else if (diagonalPos > 1.5) {
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downDiagonalResult = q12;
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}
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else {
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downDiagonalResult = q11;
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}
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}
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if (!hasUpDiagonal) return downDiagonalResult;
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if (!hasDownDiagonal) return upDiagonalResult;
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return mix(downDiagonalResult, upDiagonalResult, 0.5);
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}
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vec4 r1 = mix(q11, q21, fract(pos.x));
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vec4 r2 = mix(q12, q22, fract(pos.x));
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vec4 unqunatized = mix(r1, r2, fract(pos.y));
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float q11d = quickDistance(unqunatized, q11);
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float q21d = quickDistance(unqunatized, q21);
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float q12d = quickDistance(unqunatized, q12);
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float q22d = quickDistance(unqunatized, q22);
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float best = min(q11d,
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min(q21d,
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min(q12d,
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q22d)));
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if (q11d == best) {
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return q11;
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}
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if (q21d == best) {
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return q21;
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}
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if (q12d == best) {
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return q12;
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}
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return q22;
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}
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vec4 scale(sampler2D image)
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{
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vec2 texCoord = vec2(gl_FragCoord.x, uResolution.y - gl_FragCoord.y) / uResolution;
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vec2 pixel = vec2(1.0, 1.0) / uResolution;
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// 4-pixel super sampling
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vec4 q11 = omniScale(image, texCoord + pixel * vec2(-0.25, -0.25));
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vec4 q21 = omniScale(image, texCoord + pixel * vec2(+0.25, -0.25));
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vec4 q12 = omniScale(image, texCoord + pixel * vec2(-0.25, +0.25));
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vec4 q22 = omniScale(image, texCoord + pixel * vec2(+0.25, +0.25));
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return (q11 + q21 + q12 + q22) / 4.0;
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} |