Need a program to be able to process a image using turbo c++. i.e
reading a image file, make some modifications like changing gray scale
and alignment, height and width.

This is a nice product I've used in the past and it's free! [
http://imagemagick.org/ ]

ImageMagick is powerful but it might all be command-line-driven utilities.

There's the GD library ... http://www.boutell.com/gd/
to read and write image files of various formats from inside a program,
easy to use once you see the examples.

For clarification, the ImageMagick software suite includes Magick++,
an object-oriented C++ interface.  As noted by odmar-ga, ImageMagick
also includes a command-line driven interface for batch processing. 
GD library looks like a good product too.

I suggest the library OpenCV, very powerful computer vision and image
processing library.
http://www.intel.com/research/mrl/research/opencv/