function drawPixel(output, pos, r, g, b) {
    output[pos + 0] = r;
    output[pos + 1] = g;
    output[pos + 2] = b;
    output[pos + 3] = 255;
}
@param {Uint8Array | Uint8ClampedArray} output
@param {number} pos
@param {number} r
@param {number} g
@param {number} b