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I am trying to make a logo with a pattern of varied transparencies since the client wants a transparent png logo. No matter what I try, I cannot get the squares to line up perfectly. It looked fine as a solid object, but when I added some opacity to the squares, a small line was visible where the squares overlap.

I have done a lot of research on this and found three different ways of doing what I want, but each time the result is the same, with the same slight overlap that is noticeable when saved as a pdf or png.

I have tried using the Split into Grid tool (with 0 inch gutter), manually snapping to point, and using the align tool to distribute spacing with 0 inches. I made sure the document was set up with "Align new objects to pixel grid" unchecked. There is no stroke applied to any of the boxes. Is there some really obvious thing I am missing, or is this a flaw with Illustrator?

In this example I have made all the boxes the same color and transparency:

Different Grid Methods

  • Having difficulty seeing any problem in that small low res image. You can switch to Outline mode to align paths. It's better than trying to be precise in Preview Mode.. – Scott Feb 20 '16 at 0:37
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I have some bad news for you. There is a chance that you have absolutely nothing that can ensure this working in a PDF file on all viewers. Most vector rasterisation engines assume in antialiasation that pixel coverage is the same as pixel alpha. Because of this you get into problems with how the shape edges are drawn, individual transparent shapes makes the problem worse. Errors caused by this assumption are known as a conflation artefacts since they are caused by conflation of two unrelated issues. So it is possible that you see this even if you are perfectly accurate.

enter image description here

Image 1: Same vector drawing in two different rendering engines. The other is showing conflation (left Acrobat Pro DC) and the other is not (Illustrator GPU preview*). Note that alpha handing is in many ways different

Ok so what can you do? You can turn antialiasing off, then you dont have this problem**, if you still do then you have accuracy issues on top of this or your software has bad quantisation. If you are in control of the rasterisation process, like in PNG export, then you can use a different antialiasing scheme. By supersampling the output you get the benefits of non-antialiasing rendering and you should be better off (in illustrator this is called art optimized in PNG export). However it is certainly possible that even this fails for you if you are extremely unlucky, as doing it right requires quite an effort.

* GPU programmers have used quite much time and effort to discretitize the domain so that this does not happen.

** Depending on how pixels are quantitzed. Illustrator CPU rendering is a bit bad in these cases but the GPU preview has no problems go figure

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First, make sure you are exporting and reviewing there; sometimes Illustrator will show these lines in preview/working mode, but they won't be present when you properly export them.

Second, if you have already checked to ensure that the objects are precisely set to whole numbers in both their X and Y position and Height and Width, be sure to also check that the Artboard on which they sit is also set to whole numbers (for all 4 properties - X, Y, H, W). Select the artboard with the Artboard tool and review the coordinates in the top info bar.

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