PDF export: RGB images get converted to CMYK

[Daniel Kuhlmann]

--> Creating a new doc in 1.8.1 with CMYK/8 set as document colour

--> Placing a RGB image inside a Picture Frame Rectangle (e.g. TIFF, sRGB, 8bit)

--> Export settings PDF/X-4 ("Convert image colour spaces" not selected)

In exported PDF, the image will show as an ICC profiled RGB image if it has been neither cropped nor downsampled.

However, the image will be converted to CMYK if it has been either cropped (picture frame smaller than image) or downsampled.

I'm not sure if this is a bug or a design decision. But it would be great to be able to consistently export PDFs with embedded RGB images as it has been implemented in Publisher 1.7.3.

[Daniel Kuhlmann]

Hello Affinity,

Could someone possibly have a look at this? It would be interesting to know if this is a bug that will be fixed or if it is supposed to be like that.

Among possible advantages to leave images in RGB, I have an immediate problem with the resulting file sizes. Here is a comparison of PDF file sizes of the exact same 150 images photography book. All images were downsampled to 450ppi and JPG-compressed with maximum quality:

InDesign RGB:                   300MB
Publisher 1.7.3 RGB:     1,000MB

InDesign CMYK:                600MB
Publisher 1.8.1 CMYK:  3,600MB

We're processing lots of photography books every day and these file sizes are breaking our infrastructure.

Any help would be much appreciated.

Daniel

[Leigh]

I've been able to replicate your first issue and i've logged it with our developers to be looked at. Thanks for letting us know.

 

[Leigh]

Is it possible to upload some example documents to our dropbox account using the below link? This will allow us to look into this further for you.

<LINK REMOVED>

[Daniel Kuhlmann]

Hi Leigh,

Many thanks for your reply. I've attached a PDF that shows the result of my export tests with various images types. Unexpected behaviour is marked in red. 

I've also uploaded the JPG sRGB 8bit images plus Publisher and InDesign files using your dropbox link. I can upload the other variants as well, if needed.

Please do not publicly share screenshots of uploaded images.

Many thanks again,
Daniel

Publisher PDF Export.pdf

[Leigh]

Thanks for uploading the examples. I will take a look and reply when I have an update.

[Leigh]

I've not forgotten about you - i'm waiting for our QA team to get back to me.

[Leigh]

It appears that InDesign uses Bicubic by default and we're using Bilinear. In 1.8 we've also changed the JPEG compression for HQ presets to use 98% compression instead of 85%. Do you know what compression you're using in Indesign for images when exporting to PDF?

[Daniel Kuhlmann]

Thanks for the feedback, Leigh.

I think we have two issues here. One is file size and the other is unwanted conversion to CMYK.

Regarding the file size, in InDesign I was using bicubic downsampling with a compression of "Automatic (JPEG)" and "Maximum" image quality. The Publisher export file sizes I uploaded are based on bicubic sampling and 100% compression quality as well. So both settings should be comparable.

The more important issue for me, however, is that RGB images are being converted to CMYK in case they were cropped or downsampled, even though "Convert image colour spaces" is deselected.

Many thanks,
Daniel

[Leigh]

I'm sorry for the delay in replying. 

You definitely have two issues and the latter one is logged with our developers to be fixed. It would be interesting to know the percentage of the compression used in Indesign when Maximum is used but I will take another look at your files.

[Daniel Kuhlmann]

Thanks for your reply, Leigh.

Great to hear that you are working on a fix. I could not find any infos on the percentage of compression InDesign uses but interestingly, RGB or CMYK does not differ in size with InDesign. 

Take care,
Daniel

[Leigh]

Hi Daniel, I just wanted to let you know that we've released a new beta build today that should fix your issue with PDFs exporting RGB profiles to CMYK. Is it possible to give it a try to see if it resolves your issue?

[Daniel Kuhlmann]

Thanks a lot, Leigh & team!

We really appreciate that you keep working on this despite Corona.

I can confirm that RGB color profiles are being respected during export now. ProPhoto RGB, Adobe RGB and sRGB have the correct profile in the exported PDF.

However, the bit depth is still not respected. When I export a 16bit RGB image that has neither been downsampled or cropped by Publisher, the PDF correctly includes a 16bit RGB image. If the image has been downsampled or cropped by Publisher, though, the PDF shows an 8bit RGB image. 

Although there are not many use cases for 16bit images in PDFs, I assume that it will lead to possible confusion and errors if 16bit and 8bit images get unintentionally mixed, just depending on whether they were cropped in Publisher or not.

Should I post this issue in the beta forum or are we going to follow up in this thread?

Many thanks,
Daniel

[Leigh]

Thanks for the feedback - happy to hear that RGB profiles are now being honoured.

If you could log the 16bit/8bit issue against the beta version, that would be great.

[Patrick Connor]

This fix has been rolled out as part of the 1.8.3 release