Publisher PDF export: JPG compression has no effect

[SveBjorn]

Windows 10

Affinity Publisher 1.10.4.1198

Tried many settings combinations but the JPG compression doesnt have any effect on filesize.

 

[lacerto]

Do you have imported PDFs that have been marked to be passed through? (These will not be affected by compression settings.) Also, do you mean that turning off and on the JPEG compression (with the default quality setting) does not affect the file size? Or do you mean that changing the quality setting does not have any effect?

As the causes can be varied, an example .apub document with content that is not affected by compression settings would be useful.

[thomaso]

For certain image file types and/or color depths on PDF export not JPG compression gets used but a different compressor (macOS: zlib/deflate).

[Fixx]

Filesize of afpub file or exported PDF? What kind of images you have imported to layout?

[SveBjorn]

Most images are JPG or PSD. Some are TIFs. So pretty mixed.

I found a way to have an effect now - I use Flattened images when exporting.

[thomaso]

Can you upload an affected .afpub with one (or more) image (not flattened, embedded or separate)?

[Wosven]

I did some tests for another thread and JPG compression was used even when not needed (for example, if set only for images above 300 PPI, images at 270 and at 300 were also compressed):

 

I had no time to do test again to check what the result of their discussion is, but:

 

[Callum]

This is a known issue that is currently logged with our developers to be fixed in a future version, hopefully it wont be too long until this is solved. I will update this thread if I get more info.

Thanks All
C

[thomaso]

Just in case: it reminds me to this thread about JPGs not getting compressed on PDF export. (The thread appears not to be tagged.)

There apparently resolution & size could cause the issue, with one workaround to lightly scale them in the layout:

Quote

So the issue affects in particular those resources whose Original DPI = Documents DPI = Placed DPI. (e.g. all 300 dpi).
(…)
It becomes more strange (or more logical) that a change in size from 100 to 99,9 % is sufficient to result in the wanted export JPG quality.

Also, the color space seems to influence the issue, as Gabe mentioned in their summary:

On 6/3/2020 at 5:06 PM, Gabe said:

So we've found 3 issues:

1. If you have a 300DPI document and place a 300DPI image and a 72DPI image, jpeg compression only works on the 72DPI image. Using the PDF x4 Preset
2. Same setup as #1, the 72 image gets converted to CMYK for some reason, while the other doesn't.
3. That image you've attached which reports 72dpi even though it's 300. 

The document I was using was CMYK with RGB images, so that's why mine was working. This is the afpub I was using to find #1 and #2