mirror of https://github.com/mgba-emu/mgba.git
40 lines
1.1 KiB
Forth
40 lines
1.1 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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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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// texel arrangement
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// A B C
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// D E F
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// G H I
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vec4 B = texture2D(tex, texCoord + vec2( 0.0, o.y));
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vec4 D = texture2D(tex, texCoord + vec2( -o.x, 0.0));
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vec4 E = texture2D(tex, texCoord + vec2( 0.0, 0.0));
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vec4 F = texture2D(tex, texCoord + vec2( o.x, 0.0));
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vec4 H = texture2D(tex, texCoord + vec2( 0.0, -o.y));
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vec2 p = texCoord * texSize;
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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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gl_FragColor = B == F && B != D && F != H ? F : E;
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} else {
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// Bottom Right
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gl_FragColor = H == F && D != H && B != F ? F : E;
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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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gl_FragColor = D == B && B != F && D != H ? D : E;
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} else {
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// Bottom Left
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gl_FragColor = D == H && D != B && H != F ? D : E;
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}
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}
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}
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