uniform sampler2D maintex;
uniform float factor;
varying vec2 uv;
void main() {
    vec4 c = texture2D(maintex, uv);
    vec4 r;
    // when these become vectorized, they need to turn scalar
    // arguments into proper types as well
    r.x = max(0.123, c.x);
    r.y = max(0.123, c.y);
    r.z = min(c.z, factor);
    r.w = min(c.w, factor);
    gl_FragColor = r;
}