There are quite a number of different graphics file formats in use, so often we need a software to use for some image conversions 

ABC Amber Image Converter is an advanced tool to convert your image files (BMP, WMF, EMF, ICO, JPG, GIF, PNG, TIFF, PCX, PCC, DCX, PBM, PGM, PPM, TGA, etc).
The software supports a batch conversion, a run from command line, more than 50 languages and comes with a embedded viewer.