When covering one vector shape with another; if the edges overlap, the background shape’s color is used as a (distasteful looking) pseudo-anti-alias effect on the foreground shape’s edge, instead of having the foreground shape’s color blend in with the color of whatever is outside both shapes. (Wow, I’m not sure if I made any sense describing this.)
I can cope with this happening within Illustrator, but why does it have to happen in any exported vector formats as well? For instance, when rendering logos in .EPS format, how do you deal with this annoying phenomenon? Is there any way to circumvent it without having to manually offset (trap?) the background object’s edge so as not to get this undesired effect?
Choosing “Save for Web” in Illustratos seems to always render perfect results. But somehow (maybe someone can explain the technical reason) vector formats won’t regard the behind-object to be entirely covered by the frontmost object (i.e. disregard the lower object’s edge), but instead insist on “spilling” in its color onto the edge of the frontmost object.
To wrap it up:
I’m mainly looking for advice/approaches when dealing with this, especially within context of logotype crafting, where deliverables may often be requested in .EPS format, apart from normal bitmap formats.
EDIT: one thing I find interesting is that when doing “Save for Web” and switching between Art Optimized and Type Optimized, the latter will also exhibit this undesired phenomenon.
This isn’t really an Illustrator issue, but a general problem when vector art is rasterized. Displaying vector art on a pixel-based screen involves rasterizing just as exporting vector art to a pixel-based image format does.
Why is “Save for Web” better at this? Difficult to say, but it might require relatively slow, complex calculations to give the best result, which would be unacceptably slow if applied in real-time while you’re editing.
I would imagine there are academic papers on this if you want to look into it further.
When supplying vector logos, it would definitely be best practice to eliminate the possibility of the issue occurring.
In your examples, you could either nudge the foreground object up and to the left, or subtract a copy of the foreground object from the background object and ensure that no traces of the background object remain at upper left.
Source : Link , Question Author : Henrik , Answer Author : e100