[Chaco]: Hook after rendering of lines, but before render of image
I am currently trying to implement some post-processing of a rendered chaco-plot as an image. So what I would need is some sort of hook, to get to know, whenever a new draw-request is performed for Chaco. Once I am called in this hook, the layout of the Chaco-Plot should already be present, so that I can grab the rendered image, modify it and then draw it pixel-perfect over the original area.
I would be thankful for any kind of advice how to achieve this.