Hi, I need to develop a software that selects a face from a photo where the background is a plain color (green, like in the movies).
Then we want to compose that selection with another background image, this part is easy with many libraries. But I don't know how can I do the selection? Can you give some links or libraries to investigate? I can do this project with any language of my choose, so examples or links in any language are welcome.
Ok, what you are trying to do is called chroma key. Like you say, it used a lot in the movies with a blue/green screen. On windows its actually pretty easy to do because its built into windows as part of GDI+ (or on C#, I think its just called the Graphics class).
I dont have any sample code handy, but the process is pretty straight forward:
With GDI+, you create a bitmap object of your foreground image (the one with the green background). Then create an ImageAttributes object. Use ImageAttribute's object's SetColorKey() method to specify a color or range of colors to use as the background color. Lastly, draw that bitmap object over the target bitmap, and GDI+ will draw it as if the background color is transparent.
There's more to it in that in code, but concept-wise thats all there is to it.
This is probably an area where it is easier to work in some other space than RGB - such as HSV.
I would also look at the OpenCV library.