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