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Old 10-20-2026, 01:59 AM   #1
paulfiera
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Compress Images Losslessly
Is it possible to add this function as stand-alone to the context menu?

I am using it on some books with great results but I need to 'Edit book' first

Many thanks!
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Old 10-20-2026, 02:14 AM   #2
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It is already present in the polish books tool which you can run by adding it to the toolbar or context menu via Preferences->Toolbars
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Old 10-20-2026, 02:53 AM   #3
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Thanks, Kovid

That was it. Perfect!
Last edited by paulfiera; 10-20-2026 at 04:47 AM.
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Old 10-20-2026, 04:50 AM   #4
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Quote:
Originally Posted by kovidgoyal View Post
It is already present in the polish books tool which you can run by adding it to the toolbar or context menu via Preferences->Toolbars
Thought I'd make a new post. :-)

Somehow, the Compress Images in Polish Books works different than the utility in Edit Book.

Using the one in Polish Books, I get this output (on all images with different names):
f01-02_fmt.jpeg could not be further compressed


Using the one in Edit Book I get this output (on all images with different names, different compression ratio but all get compressed):
f01-02_fmt.jpeg compressed from 27.5 KB to 11 KB bytes [59.9% reduction]
Last edited by paulfiera; 10-20-2026 at 05:15 AM.
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Old 10-20-2026, 06:08 AM   #5
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If it "could not be further compressed," that just means it's already been run on that image. Are you saying that after running Polish Books and compressing the images there, when you compress those already-compressed images in that same book in the Editor, it says it's compressing them again?
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Old 10-20-2026, 06:27 AM   #6
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Quote:
Originally Posted by enuddleyarbl View Post
If it "could not be further compressed," that just means it's already been run on that image. Are you saying that after running Polish Books and compressing the images there, when you compress those already-compressed images in that same book in the Editor, it says it's compressing them again?
What I've done with one epub for testing purposes is:

I run the Compress Image tool in Polish Books, and all the images in the book return "could not be further compressed" so no compression happens and the epub size remains the same.

After that, I run the Compress Image tool in Edit Book on the same epub and the images are successfully compressed, the different compression ratio for each image is displayed and the epub size is reduced immediately after saving.

The reason might be that with Edit Book you can enable lossy compression, which you can't with Polish Books
Last edited by paulfiera; 10-20-2026 at 07:32 AM.
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Old 10-20-2026, 08:28 AM   #7
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Polish books is pure lossles only. Edit book allows you to do lossy since you can manually review and revert changes.
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Old 10-20-2026, 08:43 AM   #8
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Quote:
Originally Posted by kovidgoyal View Post
Polish books is pure lossles only. Edit book allows you to do lossy since you can manually review and revert changes.
That's it.

Thanks, Kovid
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