<style>
    canvas {
        width: 100px;
        height: 100px;
    }
</style>
<script>
    function run() {
        var c = document.querySelector("canvas");
        c.width = 1;
        c.height = 1;
        var ctx = c.getContext("2d");

        ctx.fillStyle = "rgba(255, 180, 0, " + 163/255 + ")";
        ctx.fillRect(0, 0, 1, 1);
    }

    window.addEventListener("load", run, false);
</script>
<canvas></canvas>