I am not at all versed in Computer Graphics and am in need of creating a color picker as a javascript tool to embed in an HTML page.

First, and looking at Photoshop's one, i thought of the RGB palette as a three-dimensional matrix. My first attempt envolved:

<script type="text/javascript">
        var rgCanvas = document.createElement('canvas');
        rgCanvas.width = 256;
        rgCanvas.height = 256;
        rgCanvas.style.border = '3px solid black';
        for (g = 0; g < 256; g++){
            for (r = 0; r < 256; r++){
                var context = rgCanvas.getContext('2d');
                context.beginPath();
                context.moveTo(r,g);
                context.strokeStyle = 'rgb(' + r + ', ' + g + ', 0)';
                context.lineTo(r+1,g+1);
                context.stroke();
                context.closePath();
            }
        }

        var bCanvas = document.createElement('canvas');
        bCanvas.width = 20;
        bCanvas.height = 256;
        bCanvas.style.border = '3px solid black';       
        for (b = 0; b < 256; b++){
            var context = bCanvas.getContext('2d');
            context.beginPath();
            context.moveTo(0,b);
            context.strokeStyle = 'rgb(' + 0 + ', ' + 0 + ', ' + b + ')';
            context.lineTo(20, b);
            context.stroke();
            context.closePath();
        }

        document.body.appendChild(rgCanvas);
        document.body.appendChild(bCanvas);
    </script>

this results in something like

My thought is this is too linear, comparing to the ones i see in Photoshop and on the web. I would like to know the logic behind the color mapping in a picker like this:

I don't really need the algorythms itself, i'm mainly trying to understand the logic.

Thanks