Do I need to some information about the tiff file in order to proceed?
You'll need to know the size of the pixels for a start, and you could use GDAL for that, see:
How do I find out the resolution in (centimeters per pixel) of a TIF?
I am new to both ENVI and IDL. I am not much familiar with their
environment so I couldn't do anything on that. However, suggestion for
any other platform is also appreciated.
As far as using IDL to call GDAL, though, it doesn't look like it's possible; there is a discussion on the gdal-dev mailing list about this point. With a conclusion to just use Python.
IDL and Python Numeric have a similar syntax and perhaps you would
find it easiest to just write your routines in Python
This page is a summary of the mapping between IDL and numarray
There are quite a few questions on gis.stackexchange that deal with GDAL+Python+Tiff, so you should be able to get enough of a hint to progress.