Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I'm trying to reduce file size of a bunch of JPEG files, say 1280x720. Without changing the resolution and the visual quality much, what are the recommended approach?

share|improve this question

JPEG is based on DCT and entropy encoding. If your image is not entropy-optimized yet, there might be a chance to reduce the size.

If you have a Debian or any other Linux system, try using jpegoptim from the same named package, or jpegtran from libjpeg-progs. The man page of jpegtran states that it is lossless:

jpegtran works by rearranging the compressed data (DCT coefficients), without ever fully decoding the image. Therefore, its transformations are lossless: there is no image degradation at all, which would not be true if you used djpeg followed by cjpeg to accomplish the same conversion.

I also found the following two tools, which I've never tried:

share|improve this answer

If the curent image size is larger that 1280 x 720 (which is likely if these are camera images) then the best way is to reduce the number of pixels to 1280 x 720.

If they are already at 1280 x 720, then the easiest way is to reduce the JPEG quality. Most imaging software has some way of changing this, and a lower quality will reduce the file size. You'll need to check wehther the quality is still acceptable though.

Another way may be to save the file as a GIF or BMP with compression. This will only help with simple, flat-colour images though, not with photos.

I don't know what software you are using, but I can recommend Irfanview

share|improve this answer
Thanks, I was more hoping for a set of tweak settings when saving as new JPEG. – lang2 Aug 14 '12 at 7:27
GIF will effectively kill the image, as it will be reduced to 256 colors. – Bobby Aug 14 '12 at 8:01
@Bobby correct, but if the image is suitable it will really reduce the size. Lang2 Changing the quality setting is just that, a tweak of the settings. Changing the image size requires another action before saving it. – hdhondt Aug 14 '12 at 10:50

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.