Memory optimization

[wolfgangmeyers]

Hello,

I've been working on optimizing the memory of an application I am working on, and I noticed that the context.Fill method creates a new Rasterizer each time it is called. This probably isn't noticeable in most use cases, but in my case the rendering is being used very heavily, and I noticed a lot of the memory allocation in my application came from this method:

https://github.com/fogleman/gg/blob/master/context.go#L397

Would it be possible to reuse the rasterizer for multiple calls to Fill ?

[fogleman]

That should be possible. Feel free to submit a PR or I can try to do it later (currently on vacation!)

[wolfgangmeyers]

Thanks!