You can compare speed and memory use like this:
$ /usr/bin/time -f %M:%e vipsthumbnail big.jpg --size 256x256 -o x.jpg
58180:0.20
$ /usr/bin/time -f %M:%e convert big.jpg -resize 256x256 x.jpg
717356:1.39
The output is peak memory use in kb, elapsed time in seconds. This is a 10k x 10k pixel JPG.
10 months ago