reading and writing an image

[prashanth34]

Hi everyone,

I'm learning to do image processing using C++.Since I'm new to this type of programming ,I would really appreciate if some one can help me reading and writing an image.

[helios]

What library are you using?

[prashanth34]

Is there any special library for image processing? We are asked to use only standard library files(stdio.h).

[helios]

Depends on what kind of image file you're going to process. bmps can be manually edited easily. PNGs, JPEGs, GIFs, etc. are too complex to be processed without a library.
There was a thread about BMPs not long ago: http://www.cplusplus.com/forum/beginner/4307/

[prashanth34]

Image is of PPM and PGM format. If you can say any specific library to use for reading these images and also how to read/write these images.

[helios]

Oh, easy enough.
http://en.wikipedia.org/wiki/Portable_pixmap
http://en.wikipedia.org/wiki/Portable_Gray_Map

[exception]

Are you asked only to use the standard library files to *process* the image or also for reading/writing? The one has little to do with the other (special cases as jpeg in combination with Fourier Transform excluded, but even then you usually read the jpeg, reverse the discrete cosine transform and perform the ft, because jpeg splits the image into 8x8 pixel blocks before applying the dct (for complexity reasons) and for processing you usually want the image transformed as a whole). And you don't learn much about image processing by reading and writing all kinds of image formats. So for reading/writing, you perhaps are allowed to use libpng, libjpeg etc. For processing, although you aren't allowed to use it, you might want to have a look at octave, a free program which is in respect to image processing quite similar to matlab.