mirror of https://github.com/mgba-emu/mgba.git
55 lines
1.9 KiB
Forth
55 lines
1.9 KiB
Forth
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/* Shader implementation of Scale2x is adapted from https://gist.github.com/singron/3161079 */
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varying vec2 texCoord;
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uniform sampler2D tex;
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uniform vec2 texSize;
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vec4 scale2x(vec4 pixels[5], vec2 p) {
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// texel arrangement
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// x 0 x
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// 1 2 3
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// x 4 x
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// p = the texCoord within a pixel [0...1]
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p = fract(p);
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if (p.x > .5) {
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if (p.y > .5) {
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// Top Right
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return pixels[0] == pixels[3] && pixels[0] != pixels[1] && pixels[3] != pixels[4] ? pixels[3] : pixels[2];
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} else {
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// Bottom Right
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return pixels[4] == pixels[3] && pixels[1] != pixels[4] && pixels[0] != pixels[3] ? pixels[3] : pixels[2];
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}
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} else {
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if (p.y > .5) {
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// Top Left
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return pixels[1] == pixels[0] && pixels[0] != pixels[3] && pixels[1] != pixels[4] ? pixels[1] : pixels[2];
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} else {
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// Bottom Left
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return pixels[1] == pixels[4] && pixels[1] != pixels[0] && pixels[4] != pixels[3] ? pixels[1] : pixels[2];
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}
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}
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}
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vec4 scaleNeighborhood(vec2 p, vec2 x, vec2 o) {
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vec4 neighborhood[5];
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neighborhood[0] = texture2D(tex, texCoord + x + vec2( 0.0, o.y));
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neighborhood[1] = texture2D(tex, texCoord + x + vec2(-o.x, 0.0));
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neighborhood[2] = texture2D(tex, texCoord + x + vec2( 0.0, 0.0));
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neighborhood[3] = texture2D(tex, texCoord + x + vec2( o.x, 0.0));
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neighborhood[4] = texture2D(tex, texCoord + x + vec2( 0.0, -o.y));
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return scale2x(neighborhood, p + x * texSize);
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}
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void main() {
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// o = offset, the width of a pixel
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vec2 o = 1.0 / texSize;
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vec2 p = texCoord * texSize;
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vec4 pixels[5];
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pixels[0] = scaleNeighborhood(p, vec2( 0.0, o.y / 2.0), o);
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pixels[1] = scaleNeighborhood(p, vec2(-o.x / 2.0, 0.0), o);
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pixels[2] = scaleNeighborhood(p, vec2( 0.0, 0.0), o);
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pixels[3] = scaleNeighborhood(p, vec2( o.x / 2.0, 0.0), o);
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pixels[4] = scaleNeighborhood(p, vec2( 0.0, -o.y / 2.0), o);
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gl_FragColor = scale2x(pixels, p * 2.0);
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}
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