Custom shape and fill in HTML5 canvas

I have a small project I am working on HTML5 canvas and I wanted to get some ideas how to accomplish it. I have built an outline of a tree using all the canvas line functions. lineTo, bezierCurveTo, quadracticCurve, etc. I have attached a picture of the outline. Now, what I would like to do is have some code that fills a percent of this outline. Kind of like a progress bar s开发者_如何学Gotarting from the bottom. Does anyone have ideas on how to accomplish this?

Thanks

Rather than thinking of the problem as having to fill a percentage of the inside of the tree, why not split the image into two layers, the tree and the "fill", and then draw one over the other. See my image below for a quick and dirty example.

Of course, you will need to obscure the rest of the "fill" layer, so you will need to fill the outside of the tree shape white, but this should be fairly easy as you already have the path worked out. In essence, your path would instead of being the outside edge of a a tree shape, become the inside edge of a tree shaped hole!