I'm looking for the fastest command-line image converter for Linux which can read a JPEG image, scale it down to at most 1366x768, and write a quality 50 JPEG image. Something like this, but much faster than ImageMagick:
$ convert -resize x768 -quality 50 foo42.jpg foo42.th.jpg # takes 0m16.713s for my test image set
I've also tried this:
$ <foo42.jpg djpeg | pnmscale -xysize 1366 768 | cjpeg -quality 50 >foo42.th.jpg # takes 0m12.007s for my test image set, and has lower visual quality than ImageMagick
So I'd like to have a program, preferably written in C, which integrates djpeg, a higher quality version of pnmscale, and cjpeg.
I've just found swiggle (a C program using libjpeg), I've disabled some of it's functionality I don't need in the source code, and I've got:
$ swiggle -f -H 768 . # takes 0m11.378s for my test image set, yields high quality results
Do you have another suggestion? I guess most image converters use libjpeg, so it would be hard to get much faster results than swiggle.