image processing- Converting a coloured image into a black and white image)

[Anusha777]

Hi,
I am working on a C algorithm to convert colour images to b/w images.
Can anyone tell me how to start up at this?
I will be grateful if somebody suggest me website references that help me to complete my project. (my project is all about taking a bitmap image and converting it into b/w image)
Thank you :)