[Defold] Fragment shader

varying mediump vec4 position;
varying mediump vec2 var_texcoord0;
varying lowp vec4 colors[10];

uniform lowp sampler2D DIFFUSE_TEXTURE;
uniform lowp vec4 tint;
uniform lowp vec4 saturation;

void main()
{
    lowp vec4 tint_pm = vec4(tint.xyz * tint.w, tint.w);

    lowp vec4 initial_color = texture2D(DIFFUSE_TEXTURE, var_texcoord0.xy);
    // Convert red channel to index [0..9]
    lowp int index = int(floor(min(initial_color.x * 10.0, 9.9)));
    // Use that index to get the new color from colors array
    lowp vec4 color = colors[index];
    // Save the original alpha channel value
    color.w = initial_color.w;

    {
        color.x = (color.x * (1.0 - saturation.w) + saturation.x * saturation.w) * color.w;
        color.y = (color.y * (1.0 - saturation.w) + saturation.y * saturation.w) * color.w;
        color.z = (color.z * (1.0 - saturation.w) + saturation.z * saturation.w) * color.w;
    }

    gl_FragColor = color * tint_pm;
}