Image compression with ICCBased color space

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Puffolino
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Image compression with ICCBased color space

Post by Puffolino »

I have some scanned documents which seem to be "perfectly" compressed - all images are shown with a color space "ICCBased" within the PDF Editor. As soon anything will be changed (like cropping a side of such an image or trying a recompress) the image size grows massively.

BTW cropping a single page woud be fine as well as a special cropping function which works for a selected image would be a cool enhancement for me :roll:
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Paul - Tracker Supp
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Re: Image compression with ICCBased color space

Post by Paul - Tracker Supp »

Hi Puffolino,

is this limited to certain documents? Do you have a sample for us?
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Paul O'Rorke
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Puffolino
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Re: Image compression with ICCBased color space

Post by Puffolino »

I'll keep an eye to find some good examples, but actually I am checking why cropping an image makes a file larger in all (?) cases as it seems to add some junk information to the PDF file?
I did some tests for now and was wondering that my PDF files gets larger and larger each time I cropped an image outside a page. When I checked "Audit space usage" for these files, the "Document Overhead" size has increased also each time. Doing "Optimize PDF" never removes that overhead, extracting all pages to a new document does the trick 8)

Not sure if the ICCBased color space should be available as an option within the "Recompress image" options as well? :roll:
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Re: Image compression with ICCBased color space

Post by Paul - Tracker Supp »

Hi again Puffolino,

I asked the dev team about this and they are asking for a document. There is something going on here that does need to be looked into.

cheers
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Puffolino
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Re: Image compression with ICCBased color space

Post by Puffolino »

Hi, not at home for some days but tried to upload a test file to https://useruploads.tracker-software.support which did not work from here (page not available).
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Re: Image compression with ICCBased color space

Post by Paul - Tracker Supp »

Hi Puffolino,

The service is back up, try it now.
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Puffolino
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Re: Image compression with ICCBased color space

Post by Puffolino »

The behaviour is not limited to ICCBased images, I just uploaded a pdf file containing "standard" RGB coded images.
You should see an increase of the file size when doing remove cropped content. The file size won't change when pages are deleted.
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Re: Image compression with ICCBased color space

Post by Paul - Tracker Supp »

We have the file, thanks for that.

I am not seeing an increase in file size when I recompress an image. I used these default settings:



Similarly, I did an arbitrary crop on the second page and using again just defaults:



I get this and a smaller file size



What should I be doing to reproduce the reported increase in file size?
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Puffolino
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Re: Image compression with ICCBased color space

Post by Puffolino »

Will have a look about recompressing, maybe I'll upload another file when I'm back home. The uploaded file does show the two effects I wrote above: just start the remove cropped content function or delete some (or nearly all) pages, the file size will be increased in both cases.

Maybe I can find a nice file here, so an additional question: is there a possibility to see the original jpeg compression level (0-100%) of an image within a PDF file? Or is there a chance to extract the image without any changes? When extracting an image with the PDF Editor or PDF Tools the resulting JPG file is often larger than the original PDF file wich contains the image.
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TrackerSupp-Daniel
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Re: Image compression with ICCBased color space

Post by TrackerSupp-Daniel »

Hello, Puffolino

Thank you for the added information, I have managed to reproduce the issue with the "remove cropped content" function. I am not certain that can be resolved simply due to how the crop functions works. When cropping normally, without removal of content, the original page is unchanged, and as your expect, a bit of "extra" information is added, to change the "display area" of each page. This causes a very small growth with the crop pages tool when used and you choose not to remove content.

conversely, choosing to remove the content means that for anything which is partially cropped, a decision is made. Some comments, which go out of bounds will simply be deleted, text will be removed, and in some cases half a glyph could be sliced (and replaced with a new "shape" object). Images however, are the most heavily impacted. We cannot simply slice an edge and leave the file entirely unchanged, it does need to be recompressed when a change like this happens, and so in some cases, especially when an image is as heavily compressed as possible, you may see some growth. Our compression could see some improvement, but I cannot promise that this particular instance will be able to see the improvement you are looking for.

As for deleting pages, that issue I have not been able to reproduce, perhaps it has to do with the specific pages you tested deleting, but I have tried quite a few here with no troubles. Before I continue with this, can you please confirm that you are using build 358.0 of the software, and not a previous release which may be missing a fix from the latest?

Kind regards,
Dan McIntyre - Support Technician
Tracker Software Products (Canada) LTD

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Puffolino
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Re: Image compression with ICCBased color space

Post by Puffolino »

Thanks for all your efforts, 'bout cropping a lot of image tools are offering a "lossless cropping" function which seems to conserve all pixel data and so no recompression is done. Not sure if this could be done in the given case as well.

I am using build 357 actually, it will take some days until I return home and will do the next update. Deleting pages (by selecting thumbnails and pressing delete) the memory of the "document overhead" (Audit space usage) explodes and won't be removed by optimizing as well.

Maybe you could do me a favour and remove the screen shots showing the uploaded pdf. Thanks.
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TrackerSupp-Daniel
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Re: Image compression with ICCBased color space

Post by TrackerSupp-Daniel »

Hello, Puffolino

Yes, that document overhead "explosion" is the issue I could not reproduce, when I deleted pages, the overall document size went down proportionately, with almost no change to the overhead. Perhaps when you get home you can update and try that again. If it does happen, and we need to keep troubleshooting, it may be best to move to email, for the continued security of your document. In that case, please email us Via support@pdf-xchange.com with a link to this post.

And as requested, I have removed the images in this thread which related or showed fragments of your document.

Kind regards,
Dan McIntyre - Support Technician
Tracker Software Products (Canada) LTD

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Willy Van Nuffel
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Re: Image compression with ICCBased color space

Post by Willy Van Nuffel »

Maybe it has nothing to do with it, but please verify to be sure:

In File > Preferences > Documents > Save Documents, the check-box for "Always use Incremental Save", is it turned off ?
If not, the size of the PDF will increase after each modification.

Regards.

Willy
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Paul - Tracker Supp
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Re: Image compression with ICCBased color space

Post by Paul - Tracker Supp »

Nice one Willy,

that definitely could be what's happening here. I didn't realize this until this discussion prompted my looking into it more, but with Incremental Save enabled, even if you "delete" pages, it is only an internal reference to the pages that is changed, the pages remain.

With incremental save turned off when you save it those pages are removed.

I'd bet my ham and cheese sandwich that you nailed this Willy. And I LOVE ham and cheese sandwiches.
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Puffolino
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Re: Image compression with ICCBased color space

Post by Puffolino »

Still not sure what's going on - tested a file with 45 pages and deleted 44 pages then. Below are the audit dialogs before and after the pages have been removed. :shock:

This test has been done with build 357, the incremential saving checkbox is not enabled. So maybe you need to wait eating your sandwich... :wink:
grafik.png
grafik2.png
grafik3.png
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Paul - Tracker Supp
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Re: Image compression with ICCBased color space

Post by Paul - Tracker Supp »

So maybe you need to wait eating your sandwich... :wink:
Noooo! It must be eaten fresh! :D

Was that you emailing support@ from a different email address asking how to upload the 45 page document?

We have this file service you could use. Just make sure to either name the file something eponymous or otherwise let us know the file name so that we may associate it with this thread.
https://www.pdf-xchange.com/knowle ... le-service

I am keen to see if I can get the same as you did.
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Puffolino
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Re: Image compression with ICCBased color space

Post by Puffolino »

Paul - Tracker Supp wrote: Wed Nov 03, 2021 4:50 pm Noooo! It must be eaten fresh! :D
So you'd never thought to send me the sandwich, right? For that reason I'll aso keep my fresh baked "Apfelstrudel" here. :)

Meanwhile you got a mail - sorry for using another address.
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Re: Image compression with ICCBased color space

Post by Paul - Tracker Supp »

Well it looks like I owe you a Ham and Cheese sandwich! What kind of bread would you like? :D I am not good at baking Apfelstrudel

Reproduced with this document. I deleted all pages but the first via the thumbnails pane and sure enough the resultant document was larger! It appears we are missing some cleanup here and will investigate.

I'm sure you know the deal, the ticket is for internal use only etc... the associated ticket is RT#5783: Delete pages increases document size

we will fix this.

thanks for helping us get to the guts of the situation.
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Puffolino
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Re: Image compression with ICCBased color space

Post by Puffolino »

Hey, nice to hear that (not only the sandwich)...
...great you could reproduce this, fine that you never gave up.
Cheers
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Image compression with ICCBased color space

Post by Tracker Supp-Stefan »

:)
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PHK
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Re: Image compression with ICCBased color space

Post by PHK »

Was RT#5783 ever resolved?
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FringePhil
Willy Van Nuffel
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Re: Image compression with ICCBased color space

Post by Willy Van Nuffel »

In the version history of PDF-XChange Editor there is no immediate occurrence of item RT#5783

Instead there is an item in Build 9.5.365.0 ( 28 Nov 2022 ):
"Fixed the issue when deleting pages from a document did not always decrease the file size. (T# 6248)"

@Tracker Support
We may wonder if these two items are related?

Kind regards.

Willy
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Re: Image compression with ICCBased color space

Post by Tracker Supp-Stefan »

Hello Willy Van Nuffel,

Thanks for going through the version history!
Indeed ticket #5783 is still not marked as resolved on our end - however I would ask whether it was indeed related to 6248 and close it if it was and is already resolved!

Kind regards,
Stefan
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Re: Image compression with ICCBased color space

Post by PHK »

Tracker Supp-Stefan wrote: Thu Jul 27, 2023 12:40 pm Hello Willy Van Nuffel,

Thanks for going through the version history!
Indeed ticket #5783 is still not marked as resolved on our end - however I would ask whether it was indeed related to 6248 and close it if it was and is already resolved!

Kind regards,
Stefan
... and publish...
All best,

FringePhil
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Re: Image compression with ICCBased color space

Post by Tracker Supp-Stefan »

Hello Phil,

Indeed "and publish" :)

Kind regards,
Stefan
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