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Perform color defringing in the shader using the FreeType algorithm

This commit is contained in:
Patrick Walton 2017-09-06 16:50:36 -07:00
parent 82d2f076d7
commit cedce49a1d
1 changed files with 29 additions and 3 deletions
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32
shaders/gles2/ssaa-subpixel-resolve.fs.glsl
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@ -15,10 +15,36 @@ uniform ivec2 uSourceDimensions;
varying vec2 vTexCoord;
#define FILTER_0 (86.0 / 255.0)
#define FILTER_1 (77.0 / 255.0)
#define FILTER_2 (8.0 / 255.0)
float sampleSource(float deltaX) {
return texture2D(uSource, vec2(vTexCoord.s + deltaX, vTexCoord.y)).r;
}
// https://www.freetype.org/freetype2/docs/reference/ft2-lcd_filtering.html
float lcdFilter(float shadeL2, float shadeL1, float shade0, float shadeR1, float shadeR2) {
return FILTER_2 * shadeL2 +
FILTER_1 * shadeL1 +
FILTER_0 * shade0 +
FILTER_1 * shadeR1 +
FILTER_2 * shadeR2;
}
void main() {
float onePixel = 1.0 / float(uSourceDimensions.x);
gl_FragColor = vec4(texture2D(uSource, vec2(vTexCoord.s - onePixel, vTexCoord.t)).r,
texture2D(uSource, vec2(vTexCoord.s, vTexCoord.t)).r,
texture2D(uSource, vec2(vTexCoord.s + onePixel, vTexCoord.t)).r,
float shade0 = sampleSource(0.0);
vec3 shadeL = vec3(sampleSource(-1.0 * onePixel),
sampleSource(-2.0 * onePixel),
sampleSource(-3.0 * onePixel));
vec3 shadeR = vec3(sampleSource(1.0 * onePixel),
sampleSource(2.0 * onePixel),
sampleSource(3.0 * onePixel));
gl_FragColor = vec4(lcdFilter(shadeL.z, shadeL.y, shadeL.x, shade0, shadeR.x),
lcdFilter(shadeL.y, shadeL.x, shade0, shadeR.x, shadeR.y),
lcdFilter(shadeL.x, shade0, shadeR.x, shadeR.y, shadeR.z),
1.0);
}