I want to resize black&white pictures (drawings) to a fixed square size (e.g. 150x150 pixel). The original pictures are normally not square size.

Irfan View has a nice batch function and the Lanczos algorithm, so I could resize to 150x150 with preserving the aspect ratio. But Irfan View resizes one side to 150 pixel and the other side depending on the original aspect ratio with fewer pixel. Afterwards I can manually define a white border to fill the missing pixels (function called canvas size). Unfortunately this can't be done automatically because I have to define the borders, it isn't calculated automatically.

Does anyone know a freeware program that could do this in a batch job ? The shareware Smart Converter has exactly this function, but doesn't work correctly (maybe crippled in the trial version).

Try searching the freeware section of snapfiles.com. I've found a lot of cool (and free!) programs there. Hope that helps.

Thanks for the tip. I found a solution: Xnview (http://www.xnview.com) has a nice command line tool NConvert. Many human readable options, 400 different formats supported. Freeware for personal use. No nags, no limits, not crippled. Works fine. I build a batch with 3 lines to do the job.