I have a bunch of equal-height images in PNG format that I want to arrange horizontally into a single image, without any overlapping. I need a software that can do this either automatically (e.g. with a batch file) or with only a few mouse clicks. Neither XnView nor IrfanView seem to have this option in their batch processing repertoire. ImageMagick's montage/convert tool can do this, but it's extremely memory-inefficient and uses over 10 GB RAM for combining images with only 0.5 GP in total (at 24bpp) which is unacceptable. DipStych has a similar problem. And from what I've seen, panorama stitching software such as ICE generally can't combine images without overlapping them.
In theory this should be a trivial task: Load all images into RAM, concatenate the arrays, save to disk, done. Which software can actually do this?