color image to negative

[sm]

I know how to convert an image to negative if it is B/W. How do you convert color images to negative?

What function I can use to find out if an image file contains a color image or a B/W image?

[jpn]

Search the forums, please:

http://www.qtcentre.org/forum/f-qt-programming-2/t-negative-images-11389.html/?highlight=negative