I’m looking for a windows program (free or cheap) that has advanced options for compressing JPEG images, especially being able to apply different compression strength based on selected areas. Google doesn’t seem to show many useful results as though the times of this kind of software are gone. I’ve only been able to find Adobe Fireworks (expensive) or JPEG Optimizer (30-day trial of a program that died many years ago). JPEG Optimizer sort of works but its selective region feature is so hard to use that I haven’t been able to comprehend it.
Thanks, I’ve tried it but RIOT does not offer selective area compression and from my initial tests its compression algorithm looks inferior to others like Gimp or Photoshop. So far I achieved best results with the old JPEG Optimizer.
For example, imagine a picture of a field where the bottom half of the image is green grass and leaves (lots of detail) while the top half is blue sky with almost no details but a subtle gradient. I need to be able to set higher quality to the sky than to the green details because too low quality in the sky results in blotchy patches instead of smooth blue gradient. Whereas the green details don’t need that high quality because the same quality loss is much less visible in the tiny green leaves than the same quality loss in the sky gradient. If I can only set one quality for the whole image then in order to retain the sky in good quality I would need to increase the quality of the whole image and use up a lot of unnecessary bytes for the green details, which don’t need so much quality.
I’ve used ImageMagick but I’ve never heard it supporting selective area compression levels of jpeg. Besides, selecting image areas via command line must be an exercise for real tough guys!
I doubt Imagemagick can do it and I did not know it was possible. As you say you would need some way of masking certain areas which would in most cases mean quite a lot of user input.
There are different types of png image and you may be able to find one of those that gives a similar file size to a jpg at a better quality.
So png is not suitable at all. Clearly there is an area with lots of details (grass) and area with little details (gradient sky). Being able to use different jpeg compression on the detailed and non-detailed areas can improve the final file size quite a lot - I’ve been able to achieve results as good as 300 KB vs 400 KB (400 KB produced by Photoshop’s Save For Web and 300 KB produced by JPEG Optimizer after adjusting compression for the details and non-details).
But I hear this feature is now gone from all modern Adobe products.
So far I’ve been able to find one current product: Advanced JPEG Compressor - this is a real workhorse for squeezing everything from jpeg compression, it’s very feature rich and from my initial tests the results are superb (better than JPEG Optimizer) - and I didn’t even use the manual selective area compression but tweaked the compression levels for large detail and fine detail and colour detail. Now I need to decide if it’s worth for me to shell out the cash for this program since I rarely need such advanced options - once in a while I get to use images that benefit from selective compression but it’s not often.
So it’s this kind of software I’m interested in, if you know of any other alternatives let me know.
