How to colour a transparent part of an image programmatically in .NET

Question

I have an image created and saved manually as a file, which has a shape (e.g. a heart) that is transparent in the image, and the rest of the image has other colour. How to make the transparent shape with a specified colour programmatically in .NET, leaving the rest of the image untouched?

For example, provided is an image, which I want to fill transparent part with a colour.

http://www.sendspace.com/file/an53a1

Answer 1

It's transparent. So draw the background first in the color you want with Graphics.Clear(), then Graphics.DrawImage() to draw the image.

Answer 2

What you need is a flood fill algorithm. Please take a look at this:

http://www.codeproject.com/KB/GDI-plus/floodfillincsharp.aspx