SameBoy/Shaders/Scale2x.fsh
2016-06-14 14:11:37 +03:00

42 lines
1.4 KiB
GLSL

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