Test reading integer values from texture in Webgl

packed-texture.glsl

struct CARule {
    int type;
    int iterations;
    int bufferLength;
    
    bool[9] birthValues;
    bool[9] survivalValues;
};

ivec2 pTGetSize(sampler2D pT) {
    vec4 firstPixel = texture2D (pT, vec2(0, 0));
    
    return ivec2(
        256 * int(255. * firstPixel.r) + int(255. * firstPixel.g),
        256 * int(255. * firstPixel.b) + int(255. * firstPixel.a)
    );
}

vec2 pTGetPixelPosition(ivec2 sizePT, ivec2 intendedPixelPosition) {
    return vec2(
        intendedPixelPosition / sizePT
    );
}

vec4 pTGetPixel(sampler2D pT, ivec2 sizePT, ivec2 intendedPixelPosition) {
    return texture2D(pT, pTGetPixelPosition(sizePT, intendedPixelPosition));
}

ivec4 pTGetPixelInt(sampler2D pT, ivec2 sizePT, ivec2 intendedPixelPosition) {
    vec4 p = pTGetPixel(pT, sizePT, intendedPixelPosition);
    
    return ivec4(
        int(255. * p.r),
        int(255. * p.g),
        int(255. * p.b),
        int(255. * p.a)
    );
}

CARule pTReadRule(sampler2D pT, ivec2 sizePT, int offset) {
    CARule rule;    
    
    ivec4 p = pTGetPixelInt(pT, sizePT, ivec2(0, offset));
    rule.type = p.r;
    rule.iterations = p.g;
    rule.bufferLength = 256 * p.b + p.a;
    
    rule.birthValues[0] = true;
    
    return rule;
}

void readPackedTexture(sampler2D pT) {
    ivec2 sizePT = pTGetSize(pT);
    
    int offset = 1;
    
    pTReadRule(pT, sizePT, offset);
    pTReadRule(pT, sizePT, offset + 1);
    
}