Coloring parts of an image

Question

I have a png image of a floor plan and I want to overlay certain regions of it with different transparencies of the color red.

Some Complexities:

• The regions do not follow the lines on the floor plan strictly. Some regions cover 2-3 rooms, some cover aisles.
• The regions are not rectangular. Some are made of curved lines.

Questions

• Can I create these regions on a png image? Which file format is going to be the easiest to work with?
• How can I create these regions or mark these boundaries? Will I have to do it pixel by pixel?
• Once I have the boundaries, how do I add color? Can I use the flood fill algorithm based on these boundaries?

Thanks!

Answer 1

Since I did not need my layers to have the robustness mentioned by @pskink, I ended up using the layerlist drawable to overlay images to "shade" certain parts.

Answer 2

see my LayeredImageView How to maintain multi layers of ImageViews and keep their aspect ratio based on the largest one?

it's a ImageView that lets you add some Drawables as layers, so you can create your custom Drawable that draws your red regions by overriding draw() method