html5 canvas - Saving paths or clip areas to reuse

Question

I'm currently implementing a 2d deformable terrain effect in a game I'm working on and its going alright but I can envision it becoming a performance hog very fast as I start to add more layers to the effect.

Now what I'm looking for is a way to possibly save a path, or clipping mask or similar instead of having to store each point of the path in the terrain that i need to draw through each frame. And as I add more layers I will have to iterate over the path more and more which could contain thousands of points.

Some very simple code to demonstrate what I'm currently doing

for (var i = 0; i < aMousePoints.length; i++)
{
    cRenderContext.save();
    cRenderContext.beginPath();
    var cMousePoint = aMousePoints[i];
    cRenderContext.arc(cMousePoint.x, cMousePoint.y, 30, 0, 2 * Math.PI, false);
    cRenderContext.clip();
    cRenderContext.drawImage(cImg, 0, 0);
    cRenderContext.closePath();
    cRenderContext.restore();
}

Basically I'm after an effecient way to draw my clipping mask for my image over and over each frame

Answer 1

It looks like it is now possible with a new path2D object.

The new Path2D API (available from Firefox 31+) lets you store paths, which simplifies your canvas drawing code and makes it run faster. The constructor provides three ways to create a Path2D object:

new Path2D();     // empty path object
new Path2D(path); // copy from another path
new Path2D(d);    // path from from SVG path data

The third version, which takes SVG path data to construct, is especially handy. You can now re-use your SVG paths to draw the same shapes directly on a canvas as well:

var p = new Path2D("M10 10 h 80 v 80 h -80 Z");

Information is taken from Mozilla official site.