Banding when exporting to pdf

[R34V3r]

I recently did a personal project (rasterization bug.afdesign) and noticed something weird when exporting to pdf.

I got a pixel layer on top of a fill layer together with some text. The pixel layer looks fine when editing within designer:

When I export the pdf, there is a notice that designer wil rasterize some areas, which is the pixel layer on top of the fill layer. When opening the resulting pdf however, There seems to be some weird bands on the pixel layer:

Tried some different stuff, like converting the color profiles, testing different pdf configurations like not allowing jpeg compression etc.
The only preset that got me the same result as the designer view is to flatten the whole pdf, which ofcourse also flattened my text. I worked around the issue in the end by rasterizing the pixel layer together with the fill layer and export it as a normal "for print" pdf, but it made me wonder if this is some bug or expected behavior, as it felt a bit tedious to flatten my layer stack to make it rasterize the right way.

Can anyone shed some light on this? Thx in advance.

 

[Old Bruce]

1 hour ago, R34V3r said:

When I export the pdf, there is a notice that designer wil rasterize some areas, which is the pixel layer on top of the fill layer. 

The Fill Layer is being rasterized. If you do that rasterizing before export then nothing will be rasterized. Alternatively you could use a Rectangle in place of the Fill Layer, or best would be to just colour the Artboard.

 

I think that the behaviour of the Fill Layer affecting the rasterizing need of the PDF export is wrong and therefor a bug.

[Sean P]

R34V3r what PDF export settings are you using and what application are you using to view the exported PDF in? I can only see this when I open the PDF (Exported using default PDF for Print) in Chrome and zoom in.

If you inspect the original branch objects prior to export and change the fill layer to be black you will see a white outline going around them - after inspecting further it looks like the source images you've used have a very hard edged, non aliased alpha channel which I think is PDF viewers to show those objects the way they do. I've attached a screenshot of the Alpha Channel of what of those objects from the PDF export show, and also what they look like with a black shape underneath (essentially making it easier to see the non transparent areas of the image). You can see that fringe line around them that is likely causing PDF viewers to show those objects the way they do.

I don't believe its a bug within the software, just a side effect of the original source images you used and how PDF viewers render them. The best situation in this example would to just be to rasterise the group containing the Fill layer and those two branch images. This way the branches no longer have any transparency and sit on a flat background.
 

14 hours ago, Old Bruce said:

The Fill Layer is being rasterized. If you do that rasterizing before export then nothing will be rasterized. Alternatively you could use a Rectangle in place of the Fill Layer, or best would be to just colour the Artboard.

 

I think that the behaviour of the Fill Layer affecting the rasterizing need of the PDF export is wrong and therefor a bug.

This changes nothing. Replacing the Fill Layer with a rectangle still shows the problem when the PDF is exported and viewed in a browser (and a little bit, but not as bad in Acrobat), despite nothing getting rasterised.

[Old Bruce]

Glad it is n't a bug, I do use fill layers,

[R34V3r]

9 hours ago, Sean P said:

R34V3r what PDF export settings are you using and what application are you using to view the exported PDF in? I can only see this when I open the PDF (Exported using default PDF for Print) in Chrome and zoom in.

If you inspect the original branch objects prior to export and change the fill layer to be black you will see a white outline going around them - after inspecting further it looks like the source images you've used have a very hard edged, non aliased alpha channel which I think is PDF viewers to show those objects the way they do. I've attached a screenshot of the Alpha Channel of what of those objects from the PDF export show, and also what they look like with a black shape underneath (essentially making it easier to see the non transparent areas of the image). You can see that fringe line around them that is likely causing PDF viewers to show those objects the way they do.

I don't believe its a bug within the software, just a side effect of the original source images you used and how PDF viewers render them. The best situation in this example would to just be to rasterise the group containing the Fill layer and those two branch images. This way the branches no longer have any transparency and sit on a flat background.
 

This changes nothing. Replacing the Fill Layer with a rectangle still shows the problem when the PDF is exported and viewed in a browser (and a little bit, but not as bad in Acrobat), despite nothing getting rasterised.

Thx for the clear explanation Sean. It does make sense now.

Maybe a dumb question, but doesn't that mean the visualization method in one of the applications is wrong, or is this such an unstandardized thing? It's just that all of the pdf viewers I tried the banding appears (non chromium edge, chrome, edge, adobe reader), but loading in the pdf back in designer shows no issue. It just triggered this fear in my mind that I have to double check every time I export now in different readers to make sure it is rendered properly, and therefore cannot rely that what I see in designer is what I get in a portable export unless the exported file is opened in designer again.

In my mind, Designer should either already show the banding when editing, or the pdf should look like the editing view (at least when you disable any compression in the export settings). Or am I talking crazy here?

Edit: it's not that I really want to look for an issue here, my OCD just triggered on this and I let it drag me down the rabbit hole