What you’re describing is just a straight multiplication, which is easy enough to do but it’s also easy to put into the subpixel_mask function:
/*
A collection of CRT mask effects that work with LCD subpixel structures for
small details
author: hunterk
license: public domain
How to use it:
Multiply your image by the vec3 output:
FragColor.rgb *= mask_weights(gl_FragCoord.xy, 1.0, 1);
The function needs to be tiled across the screen using the physical pixels, e.g.
gl_FragCoord (the "vec2 coord" input). In the case of slang shaders, we use
(vTexCoord.st * OutputSize.xy).
The "mask_intensity" (float value between 0.0 and 1.0) is how strong the mask
effect should be. Full-strength red, green and blue subpixels on a white pixel
are the ideal, and are achieved with an intensity of 1.0, though this darkens
the image significantly and may not always be desirable.
The "phosphor_layout" (int value between 0 and 19) determines which phophor
layout to apply. 0 is no mask/passthru.
Many of these mask arrays are adapted from cgwg's crt-geom-deluxe LUTs, and
those have their filenames included for easy identification
*/
vec3 mask_weights(vec2 coord, float mask_intensity, int phosphor_layout){
vec3 weights = vec3(1.,1.,1.);
float on = 1.;
float off = 1.-mask_intensity;
vec3 red = vec3(on, off, off);
vec3 green = vec3(off, on, off);
vec3 blue = vec3(off, off, on );
vec3 magenta = vec3(on, off, on );
vec3 yellow = vec3(on, on, off);
vec3 cyan = vec3(off, on, on );
vec3 black = vec3(off, off, off);
int w, z = 0;
// This pattern is used by a few layouts, so we'll define it here
vec3 aperture_weights = mix(magenta, green, floor(mod(coord.x, 2.0)));
if(phosphor_layout == 0) return weights;
else if(phosphor_layout == 1){
// classic aperture for RGB panels; good for 1080p, too small for 4K+
// aka aperture_1_2_bgr
weights = aperture_weights;
return weights;
}
else if(phosphor_layout == 2){
// 2x2 shadow mask for RGB panels; good for 1080p, too small for 4K+
// aka delta_1_2x1_bgr
vec3 inverse_aperture = mix(green, magenta, floor(mod(coord.x, 2.0)));
weights = mix(aperture_weights, inverse_aperture, floor(mod(coord.y, 2.0)));
return weights;
}
else if(phosphor_layout == 3){
// slot mask for RGB panels; looks okay at 1080p, looks better at 4K
vec3 slotmask[3][4] = {
{magenta, green, black, black},
{magenta, green, magenta, green},
{black, black, magenta, green}
};
// find the vertical index
w = int(floor(mod(coord.y, 3.0)));
// find the horizontal index
z = int(floor(mod(coord.x, 4.0)));
// use the indexes to find which color to apply to the current pixel
weights = slotmask[w][z];
return weights;
}
else if(phosphor_layout == 4){
// classic aperture for RBG panels; good for 1080p, too small for 4K+
weights = mix(yellow, blue, floor(mod(coord.x, 2.0)));
return weights;
}
else if(phosphor_layout == 5){
// 2x2 shadow mask for RBG panels; good for 1080p, too small for 4K+
vec3 inverse_aperture = mix(blue, yellow, floor(mod(coord.x, 2.0)));
weights = mix(mix(yellow, blue, floor(mod(coord.x, 2.0))), inverse_aperture, floor(mod(coord.y, 2.0)));
return weights;
}
else if(phosphor_layout == 6){
// aperture_1_4_rgb; good for simulating lower
vec3 ap4[4] = vec3[](red, green, blue, black);
z = int(floor(mod(coord.x, 4.0)));
weights = ap4[z];
return weights;
}
else if(phosphor_layout == 7){
// aperture_2_5_bgr
vec3 ap3[5] = vec3[](red, magenta, blue, green, green);
z = int(floor(mod(coord.x, 5.0)));
weights = ap3[z];
return weights;
}
else if(phosphor_layout == 8){
// aperture_3_6_rgb
vec3 big_ap[7] = vec3[](red, red, yellow, green, cyan, blue, blue);
w = int(floor(mod(coord.x, 7.)));
weights = big_ap[w];
return weights;
}
else if(phosphor_layout == 9){
// reduced TVL aperture for RGB panels
// aperture_2_4_rgb
vec3 big_ap_rgb[4] = vec3[](red, yellow, cyan, blue);
w = int(floor(mod(coord.x, 4.)));
weights = big_ap_rgb[w];
return weights;
}
else if(phosphor_layout == 10){
// reduced TVL aperture for RBG panels
vec3 big_ap_rbg[4] = vec3[](red, magenta, cyan, green);
w = int(floor(mod(coord.x, 4.)));
weights = big_ap_rbg[w];
return weights;
}
else if(phosphor_layout == 11){
// delta_1_4x1_rgb; dunno why this is called 4x1 when it's obviously 4x2 /shrug
vec3 delta1[2][4] = {
{red, green, blue, black},
{blue, black, red, green}
};
w = int(floor(mod(coord.y, 2.0)));
z = int(floor(mod(coord.x, 4.0)));
weights = delta1[w][z];
return weights;
}
else if(phosphor_layout == 12){
// delta_2_4x1_rgb
vec3 delta[2][4] = {
{red, yellow, cyan, blue},
{cyan, blue, red, yellow}
};
w = int(floor(mod(coord.y, 2.0)));
z = int(floor(mod(coord.x, 4.0)));
weights = delta[w][z];
return weights;
}
else if(phosphor_layout == 13){
// delta_2_4x2_rgb
vec3 delta[4][4] = {
{red, yellow, cyan, blue},
{red, yellow, cyan, blue},
{cyan, blue, red, yellow},
{cyan, blue, red, yellow}
};
w = int(floor(mod(coord.y, 4.0)));
z = int(floor(mod(coord.x, 4.0)));
weights = delta[w][z];
return weights;
}
else if(phosphor_layout == 14){
// slot mask for RGB panels; too low-pitch for 1080p, looks okay at 4K, but wants 8K+
vec3 slotmask[3][6] = {
{magenta, green, black, black, black, black},
{magenta, green, black, magenta, green, black},
{black, black, black, magenta, green, black}
};
w = int(floor(mod(coord.y, 3.0)));
z = int(floor(mod(coord.x, 6.0)));
weights = slotmask[w][z];
return weights;
}
else if(phosphor_layout == 15){
// slot_2_4x4_rgb
vec3 slot2[4][8] = {
{red, yellow, cyan, blue, red, yellow, cyan, blue },
{red, yellow, cyan, blue, black, black, black, black},
{red, yellow, cyan, blue, red, yellow, cyan, blue },
{black, black, black, black, red, yellow, cyan, blue }
};
w = int(floor(mod(coord.y, 4.0)));
z = int(floor(mod(coord.x, 8.0)));
weights = slot2[w][z];
return weights;
}
else if(phosphor_layout == 16){
// slot mask for RBG panels; too low-pitch for 1080p, looks okay at 4K, but wants 8K+
vec3 slotmask[3][4] = {
{yellow, blue, black, black},
{yellow, blue, yellow, blue},
{black, black, yellow, blue}
};
w = int(floor(mod(coord.y, 3.0)));
z = int(floor(mod(coord.x, 4.0)));
weights = slotmask[w][z];
return weights;
}
else if(phosphor_layout == 17){
// slot_2_5x4_bgr
vec3 slot2[4][10] = {
{red, magenta, blue, green, green, red, magenta, blue, green, green},
{black, blue, blue, green, green, red, red, black, black, black},
{red, magenta, blue, green, green, red, magenta, blue, green, green},
{red, red, black, black, black, black, blue, blue, green, green}
};
w = int(floor(mod(coord.y, 4.0)));
z = int(floor(mod(coord.x, 10.0)));
weights = slot2[w][z];
return weights;
}
else if(phosphor_layout == 18){
// same as above but for RBG panels
vec3 slot2[4][10] = {
{red, yellow, green, blue, blue, red, yellow, green, blue, blue },
{black, green, green, blue, blue, red, red, black, black, black},
{red, yellow, green, blue, blue, red, yellow, green, blue, blue },
{red, red, black, black, black, black, green, green, blue, blue }
};
w = int(floor(mod(coord.y, 4.0)));
z = int(floor(mod(coord.x, 10.0)));
weights = slot2[w][z];
return weights;
}
else if(phosphor_layout == 19){
// slot_3_7x6_rgb
vec3 slot[6][14] = {
{red, red, yellow, green, cyan, blue, blue, red, red, yellow, green, cyan, blue, blue},
{red, red, yellow, green, cyan, blue, blue, red, red, yellow, green, cyan, blue, blue},
{red, red, yellow, green, cyan, blue, blue, black, black, black, black, black, black, black},
{red, red, yellow, green, cyan, blue, blue, red, red, yellow, green, cyan, blue, blue},
{red, red, yellow, green, cyan, blue, blue, red, red, yellow, green, cyan, blue, blue},
{black, black, black, black, black, black, black, black, red, red, yellow, green, cyan, blue}
};
w = int(floor(mod(coord.y, 6.0)));
z = int(floor(mod(coord.x, 14.0)));
weights = slot[w][z];
return weights;
}
else if(phosphor_layout == 20){
vec3 lcd4x[4][4] = {
{red, green, blue, black},
{red, green, blue, black},
{red, green, blue, black},
{black, black, black, black}
};
w = int(floor(mod(coord.y, 4.0)));
z = int(floor(mod(coord.x, 4.0)));
weights = lcd4x[w][z];
return weights;
}
else return weights;
}
This is the new bit:
else if(phosphor_layout == 20){
vec3 lcd4x[4][4] = {
{red, green, blue, black},
{red, green, blue, black},
{red, green, blue, black},
{black, black, black, black}
};
w = int(floor(mod(coord.y, 4.0)));
z = int(floor(mod(coord.x, 4.0)));
weights = lcd4x[w][z];
return weights;
}
