Thread: PNG to JPG
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Old 10-04-2022, 04:46 PM   #11
Liudprand
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Liudprand began at the beginning.
 
Posts: 133
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Join Date: Nov 2021
Device: Kobo Libra 2
Quote:
Originally Posted by retiredbiker View Post
I often see this. Given the quality of images on an e-ink reader, I don't care much about absolute image quality. On the Kindle or Kobo I usually can't tell the difference after I seriously change and compress images. I use ImagMagick from the command line:

1. Open the book in the editor, export all the png images to a working directory.
2. In that directory, run mogrify -format jpg *.png from a terminal, of course ImageMagick has to be installed.
3. Back in the editor, delete all the png files and import all the jpg files you made
4. In search & replace, look for .png and replace with .jpg in all text files
5. Run compress images lossily at a factor of 50.

That actually takes only a minute or two after you have done it a couple of times. When you are dealing with 40 or 50 or more images, it saves hours compared to one-by-one processing.
I know this is from a while ago, but I'm hoping it'll be useful for me, but ran into a problem. I'm not too familiar with command-line processes, but when I tried to do what I think you're suggesting in #2, I just get the response:
"'mogrify' is not recognized as an internal or external command,
operable program or batch file."
I've got ImageMagick installed, but obviously there's something I'm missing... Any tips gratefully received.
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