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