How can I modify an image at runtime?. Lets say that I want to paint a part of the image with a different color. Since I'm new on Qt a small basic example would be appreciated :) . Thanks!
check the documentation regarding the class "QImage":http://doc.qt.nokia.com/4.7/qimage.html
Just complementing what Antonio said:
You can use "QPainter APIs":http://doc.trolltech.com/4.6-snapshot/qpainter.html to paint whatever you want to in any QPaintDevice (QImage, QPicture, QPixmap and QPrinter are examples of paint devices).
Just open your QPainter on an image:
and than paint something on it
you can do a whole bunch of stuff on images as others have already replied. you can apply effects, you can do custom painting on top of it, or you can run through individual pixels in the image and modify them how ever you want, see one example I just created in this "wiki page":http://developer.qt.nokia.com/wiki/Manipulate_image_and_apply_RGB_mask