Batch image resize

I came back from Vancouver with more than 1000 photos on my digital camera, each of which is 4-6 MB when saved at the camera's maximum 4928 × 3264 resolution (with "normal" jpeg compression).

This is a bit much, and even after pruning out the bad photos (blurry, etc) there were still quite a few that I wanted to keep but had absolutely no intention of printing at poster sizes or substantially cropping. My largest monitor is 1680 × 1050, an HD TV is 1920 × 1080, and even the absurd new MacBook Pro is "only" 2880 × 1800. So I decided that 3056 × 2024 was large enough for these photos.

Next came the task of actually resizing several hundred photos. I am running OS X 10.6 (Snow Leopard). Initially I tried Gimp, but the batch-processing GUI turned out to be extremely difficult to install, and writing my own command-line scripts was more work than I was really looking for right now.

Finally I got ImageMagick, which I installing using MacPorts (a Linux-like package manager for OS X), and its mogrify program turned out to be exactly what I was looking for. The command is simply:

mogrify -resize 3056x3056 *.jpg

And the results look pretty good. This resize dropped the pixel count from 16.1 MP to 6.2 MP and average file size from 5.3 MB to 2.5 MB.