Command-line tool for lossless JPEG compression and optimization for Ubuntu

Question

I am looking for a command line lossless JPEG compression tool which will have the following functionality:

• be a command line tool with no GUI interface
• I can provide list of folders (where my potentially unoptimized images are), it will recursively goes and optimize all images inside of these folders and subfolders
• the images will be saved with the same name as they were before (substituting old unoptimized image for a new one)

Also it is not really important, it would be nice if the tool could

• Give a report (how much space per file / in total was saved)
• Could resize images as well
• Should properly handle big amount of files (> 1000)
• Remove metadata

Answer to Nick Wilde:

I do not know whom should I trust: you or people from google who created pageSpeed. When I run this jpeg through pageSpeed it says

Losslessly compressing httpS://upload.wikimedia.org/.../Lake_mapourika_NZ.jpeg could save 16.8KiB (4% reduction).

P.S. the reason to use a tool is not to save some space on my machine, the images are on the server, so optimizing images will help to save bandwidth for users viewing images. For this reason images should be viewable and archiving them is not an option.

Answer 1

After hours of playing with bash, I found a way how Google is doing it. It is using one of these 2 programs:

• jpegtran
• jpegOptim

Both of them support lossless and lossy conversion. I tried the second one, in Ubuntu as jpegoptim

.

Than to do what I want I have to do the following:

find MyDirectory/ -type d -exec sh -c '
    ls "$0"/*.jpg 2>/dev/null && jpegoptim --strip-all -t "$0"/*.jpg
' {} \;

This is doing really close to what I want. The only problem is that I see a lot of output about each file compression and I can not get rid of it with -q because it also get rid of summary. But this is the closest I was able to get with my just learned bash "skills". I asked a follow-up question on Ask Ubuntu.

It is really fast. It took it < 5 sec to process few thousands of files.

Answer 2

ImageMagik convert allows command line usage, batch processing and will convert your jpegs to jpeg2000 which may save you some space and has several other options. Unless you have made a backup first I would recommend not overwriting existing files until you have checked the conversion worked as things can go wrong with any tool.

Note that zip or targz individual jpegs normally results in an increase in size if you need to save space then tar directories and tar does have the option --remove-files to remove files as they are added to the archive. While it will not make the files smaller you will only waste space after one file rather than after each file.

For Info:

$ convert -list compress

B44 B44A BZip DXT1 DXT3 DXT5 Fax Group4 JBIG1 JBIG2 JPEG JPEG2000 Lossless LosslessJPEG LZMA LZW None Piz Pxr24 RLE Zip RunlengthEncoded ZipS

Answer 3

For a single image lossless optimization, you can use jpegtran:

jpegtran -optimize -perfect -outfile output.jpg input.jpg

---

Note that the key -perfect requires jpegtran to make a perfect, lossless optimization. If it is impossible for whatever reason (e.g. you added more keys to the command above such as rotation, resize or clip), it will fail and abort rather than producing a "wrong" result.

Answer 4

JPEG IS a lossy format - they cannot be compressed via JPEG compression losslessly. So there is no tool that can do that.

That being said there are likely tools that can optimize JPEG images - ie remove junk data though that would be minimal size savings.

Or another method would be to individually zip/7z/gzip (etc) compress them and delete the originals.

If either of those options are desired edit or create a new question.