How to pack a sprite with transparent areas

Questions & Answers
1

I have an image with a section of transpareny imported as sprite for our UI. It is beeing used as tiled list background (UI Image, Type: Tiled): there is an opaque stripe of color follow by a transparent stripe so in the end, every second list element has an opaque background.

When using this as the tiled image, there are artifacts showing up in the supposed-to-be transparent part of the tiled image. Looking at the atlas packed by unity, this artifacts comes from another sprite in the same atlas, which is packed near the opaque stripe (and the transparent stripe is not packed). Funny enough this only happens when the game is built, not in the editor, but I guess this comes from the fact that the editor does not actually use the atlas.
Now i understand that unity automatically trims sprites on packing, which is probably the source of this error, but is there any way to tell Unity not to do that for specific images?

In short, i want the transparent half of the sprite to be part of the sprite in game.

3

With unity 5.5 Sprite Compression of “High Quality” made packed sprites lose their transparency.
After changing sprite compression settings to Normal, Low Quality or None it let the transparency work again.

2

I am having this same problem and this is the only place talking about it that I can find. Did you ever find a solution?

SOLUTION: The solution seems to be to use “Full Rect” rather than “Tight” in the “Mesh Type” setting for any sprites that you are using as Tiled Sprites. This makes sense as I would imagine tiled sprites just use simple procedurally generated quads, whereas the other sprite modes can use the special cut down mesh type generated with the “Tight” setting and this will cut out any neighbouring sprites in the atlas.