how to zoom an image.

hello all.

i m new to opengl.i m using linux(fc4),gcc compiler.

i m trying to zoom an image.
can any body tell how to zoom the selected part of an image.i m trying to zoom the selected part of a tiff image ,but it is just moving the position of the image not zooming the image .i m doing this by using following 4 opengl function.


can body tell how to solve this problem.

and if i want to do pixel by pixel manipulation then how can i do that?

plz help to solve the problem.
thanx in advance…

First of all, you should post to a beginners section :-/

What exacly do you mean by “zooming the image”? Do you want to display a zoomed image on the screen? In this case you should use your image as a texture and map the part of it onto a rectangle. Varying the rectange size will give you the zoom or shrink effect (please note that the quality of zooming will be very poor, as a simple box filter is used). There are some nice tutorials about OpenGL texturing on the net (see the NeHe pages).

Also note that OpenGL is not an image manipulation library, but a graphics library. If yu want to manipulate images in high quality, you may be interesting in teh DevIL library.