professional_javascript_for_web/ch15/2DFillRectGradientExample03.htm

<!DOCTYPE html>
<html>
 <head>
    <title>Canvas Fill Rect Example</title>
 </head>
 <body>
    <canvas id="drawing" width="200" height="200">Your browser doesn't support the canvas tag.</canvas>
    <script type="text/javascript">
    
        function createRectLinearGradient(context, x, y, width, height){
            return context.createLinearGradient(x, y, x+width, y+height);
        }

        window.onload = function(){
            var drawing = document.getElementById("drawing");
            
            //make sure <canvas> is completely supported
            if (drawing.getContext){
            
                var context = drawing.getContext("2d"),
                    gradient = createRectLinearGradient(context, 30, 30, 50, 50);
            
            
                gradient.addColorStop(0, "white");
                gradient.addColorStop(1, "black");
            
                //draw a red rectangle
                context.fillStyle = "#ff0000";
                context.fillRect(10, 10, 50, 50);
            
                //draw a gradient rectangle
                context.fillStyle = gradient;
                context.fillRect(30, 30, 50, 50);
            }                
        };

    </script>
    <p>This example based on <a href="http://developer.mozilla.org/en/docs/Canvas_tutorial:Basic_usage">Mozilla's documentation</a></p>
    </body>
</html>