Illustrator Pattern Join Lines

[Matthew D Bayfield]

Hi all. Have stumbled onto a massively frustrating glitch on the Illustrator pattern tool.

I've made a seamless repeating pattern which I'm using for a series of banners. The pattern tiles seamlessly on Illustrator, but when I export as a JPEG (for my client's social media banners) a tiny joinline becomes visible on the edges of the pattern.

I've zoomed right in on the pattern on Illustrator and join lines definitely aren't there. They only show up in the exports. Anyone had any experience with this? It's a polka dot pattern so don't really have the time to manually paint the join line out every time I need to use the pattern.

Jpeg attached so you can see the issue.

[Matthew D Bayfield]

Alright for whatever reason this forum has made that banner so small you can't see the error.. Not sure what I can about that.

Another classic bit of Adobe service.

[Ton Frederiks]

Make sure that the export settings for ant-aliasing are set to Art Optimized, or you can try to use Object > Rasterize (or use the Effect > Rasterize) at 72 or 144 ppi in Illustrator

[Matthew D Bayfield]

Thanks man! So this worked(ish) but even at 300dpi the edges of the polka dots are a little fuzzy. Plus it seems insane that a program apparently as "industry standard" as Illustrator requires you to rasterize every repeat pattern in a design before you can export something for use.

Is this just a permanent flaw in the pattern tool you reckon? Be great if I didn't have to rasterize multiple layers every time I export and image / banner whatever.

[pixxxelschubser]

In which way do you have your pattern created?

For me - there is no problem with.

[federico platon]

Yes it's a common problem.

But yoy can try the following.

Fill your rectangle with the pattern you carefully made. 

(Optionally expand the pattern)

Place behind the pattern (maybe as a new fill in Appearances panel works too, easier) a copy of your object filled with the background color.

Select both and export selection, as jpg.

In my case those hair white lines disappear.

[Ton Frederiks · Accepted solution]

I believe there is a problem with export for screens / selection in 2020.

I created a dot pattern 21 X 11 pixels, filled a rectangle and exported it as a selection as png.

Anti aliasing was set to type optimized (which i believe is the default).

There should not be a problem with lines appearing, but they do.

Export As... > PNG looks fine, Export for Screens shows the problem.

Doing the same in CC 2019 does not show these lines.

I know there are workarounds (as mentioned above) and it is better to use art optimized, but there is a difference between 2020 and 2019 that should not be there.

If you'd like to try it yourself:

https://adobe.ly/2ULkwqG

[Matthew D Bayfield]

That's mad. So if I export as a JPEG with Art Optimized and 300dpi the join lines in the pattern are clearly visible. If I export a PNG with the exact same settings the join lines are not visible.

The Export As trick works.

Adobe really need to iron out these simple bugs. Constant time wasting!

Thanks so much for the help @federico_platon & @Ton_Frederiks.

[Ton Frederiks]

That could be caused by a conversion from mm, inches or point to pixels.

Illustrator is vector based and the artwork can (in theory) scaled to any size.

Images have their limitations, you cannot use a fractional pixel size, there is no such thing as half or a quarter of a pixel. Only whole pixels exist. When Illustrator has to export a fractional pixel it will generate a new pixel which can cause a visible line.

You may check the size of your pattern in pixels, and work in pixels (or points) when you want to export later to an image format.

[pixxxelschubser]

You can also try that way (like I mentioned before):

here is the file:

https://www.dropbox.com/s/vc0k42jqek2f21s/Muster_Punktmuster-mit-Aussparung_exportiert.ai?dl=0

[Ton Frederiks]

Your file still has the lines when exporting the selection as png.

But it is caused by another problem, your pattern was originally made in mm and that does not convert to whole pixels. Fractional pixels in pattern dimensions cause these anti-aliasing artifacts (lines).

[pixxxelschubser]

Please help me to understand.

Go to my first post in this thread. I uploaded an exported PNG file from that AI file. I cannot see any lines or other stranges things. All was done with Illustrator CC 2020 (24.0.2)

Can you see any lines in this uploaded image?

[Ton Frederiks]

You were probably lucky. You probably exported with Art Optimized  anti-aliasing at 300ppi

Type optimized shows the lines.

[pixxxelschubser]

Yes, indeed.

Why I should use Type optimized?

[Ton Frederiks]

You should not use Type optimized in this example, but it is the default.

[Ton Frederiks]

Illustrator works with a pixelsize as 1/72 of an inch, which makes 1 pixel in Illustrator the same as 1 point. If you use fractional pixels or export at a resolution that is not a multiple of 72 ppi you may introduce additional pixels and get anti-aliasing artifacts. That's why I said that you were lucky when exporting a pattern that contains fractional pixels at 300 ppi.