Make image grey and rectangle area colour...

[lidds]

I have created a screen capture functionality in my application that captures the entire desktop and then displays this in a picturebox on a form that is maximised. The user then can define a rectangle by draging there cursor which at the moment displays a red rectangle. What I would like to do is make the image black and white and then as the user defines their rectangle display the content of the rectangle in colour.

I have googled for ages trying to find something on this, but with no luck.

To illistrate this better they are using the same functionality in snagit 10, please see below link to a page that has a video link showing this (55 sec into video)

http://www.techsmith.com/snagit/features/win/

Thanks

Simon