bsnes/Shaders/Scale2x.fsh

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/* Shader implementation of Scale2x is adapted from https://gist.github.com/singron/3161079 */
STATIC vec4 scale(sampler2D image, vec2 position, vec2 input_resolution, vec2 output_resolution)
{
// o = offset, the width of a pixel
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vec2 o = 1.0 / input_resolution;
// texel arrangement
// A B C
// D E F
// G H I
// vec4 A = texture(image, position + vec2( -o.x, o.y));
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vec4 B = texture(image, position + vec2( 0, o.y));
// vec4 C = texture(image, position + vec2( o.x, o.y));
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vec4 D = texture(image, position + vec2( -o.x, 0));
vec4 E = texture(image, position + vec2( 0, 0));
vec4 F = texture(image, position + vec2( o.x, 0));
// vec4 G = texture(image, position + vec2( -o.x, -o.y));
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vec4 H = texture(image, position + vec2( 0, -o.y));
// vec4 I = texture(image, position + vec2( o.x, -o.y));
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vec2 p = position * input_resolution;
// p = the position within a pixel [0...1]
p = fract(p);
if (p.x > .5) {
if (p.y > .5) {
// Top Right
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return equal(B, F) && inequal(B, D) && inequal(F, H) ? F : E;
} else {
// Bottom Right
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return equal(H, F) && inequal(D, H) && inequal(B, F) ? F : E;
}
} else {
if (p.y > .5) {
// Top Left
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return equal(D, B) && inequal(B, F) && inequal(D, H) ? D : E;
} else {
// Bottom Left
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return equal(D, H) && inequal(D, B) && inequal(H, F) ? D : E;
}
}
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}