How to convert multiple images to monochrome at once?

[Timur Born]

How can I convert multiple images to monochrome (+JBIG2) at once?

- The "Recompress Image" option in the content tool allows to convert images to grayscale, monochrome or b/w, but only one image at a time.

- The "Save as Optimized" does not seem to offer any such conversion option at all.

- PDF Tools does not seem to offer any such conversion of images, or does it?!

I was trying to compress a PDF file consisting only of scanned pages to much smaller size. The scanned pages are black text on yellowish gray background, so monochrome or b/w would suffice. That would result in each single page going from over 400 kb down to only about 20 kb, much better than what "Save as Optimized" can offer. But doing this one image at a time and then changing the default settings to what I need (monochrome + JBIG2) is rather tedious.

[TrackerSupp-Daniel]

Hi Timur,I am afraid that at the moment it is not possible.
We do however have an active ticket for that request:
RT#4415: Recompress Multiple Images

Have a good day!

[David.P]

Hi all,

a strong +1 from my side for this feature request.

In my view, a color conversion option:


...best should be added to the "Save as optimized" function:


...similarly as it is already possible when printing (e.g. to PDF):


Thanks and keep up the great work!
David

[Tracker Supp-Stefan]

Hi David,

Thanks for the post and suggestions.
I believe what you mention has already been considered, but there are usually quite a few tasks in our list, so this one has not yet made it through!
I can't promise if or when it might be added, but is is being considered!

Regards,
Stefan

[Timur Born]

I noticed that the "Recompress Image" option is affected by "Undo", but not by "Redo". I assume this is a small bug?!

[David.P]

- deleted by myself due to stupidity -
Referenced Post deleted by moderator

Yeah, recompression should be better than reprinting because with the former, you have better control of image size and dpi. Also, sometimes you might want to keep things like bookmarks, hyperlinks etc. (which doesn't work with reprinting), but still change the color depth of all images in an entire file.

Also thanks to Stefan for the comment and for considering this as feature request!

[Timur Born]

I noticed that XChange Standard offer "Text Image Data" while Editor does not. Isn't this the method that caused issues of replaced scanned numbers on Xerox copiers?

[Timur Born]

- deleted by myself due to stupidity -

Yeah, recompression should be better than reprinting because with the former, you have better control of image size and dpi. Also, sometimes you might want to keep things like bookmarks, hyperlinks etc. (which doesn't work with reprinting), but still change the color depth of all images in an entire file.

I noticed that due to hitting "Undo" before doing screenshots I compared the reprinted version with a *not* recompressed version. Anyway, while I would prefer to get better support for multiple (as in all selected or at least all images) recompression, doing a reprint is good enough for my current usage case. I just didn't think of it myself, so thanks to David.

[TrackerSupp-Daniel]