42 lines
1.4 KiB
GLSL
42 lines
1.4 KiB
GLSL
/* Shader implementation of Scale2x is adapted from https://gist.github.com/singron/3161079 */
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vec4 scale(sampler2D image)
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{
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// o = offset, the width of a pixel
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vec2 o = 1.0 / textureDimensions;
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vec2 texCoord = vec2(gl_FragCoord.x, uResolution.y - gl_FragCoord.y) / uResolution;
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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 A = texture(image, texCoord + vec2( -o.x, o.y));
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vec4 B = texture(image, texCoord + vec2( 0, o.y));
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vec4 C = texture(image, texCoord + vec2( o.x, o.y));
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vec4 D = texture(image, texCoord + vec2( -o.x, 0));
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vec4 E = texture(image, texCoord + vec2( 0, 0));
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vec4 F = texture(image, texCoord + vec2( o.x, 0));
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vec4 G = texture(image, texCoord + vec2( -o.x, -o.y));
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vec4 H = texture(image, texCoord + vec2( 0, -o.y));
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vec4 I = texture(image, texCoord + vec2( o.x, -o.y));
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vec2 p = texCoord * textureDimensions;
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// p = the position 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 B == F && B != D && F != H ? F : E;
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} else {
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// Bottom Right
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return 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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return D == B && B != F && D != H ? D : E;
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} else {
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// Bottom Left
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return D == H && D != B && H != F ? D : E;
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}
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}
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} |