What Are The Benefits Of Tile Overlap?

Question

Just starting out playing with OpenSeadragon (very good btw) and on creating a custom tile set am wondering what the advantages or disadvantages of creating tiles with an overlap?

I've tried using 0 and it seems ok, but I wonder if there are any clarity or performance advantages or having the tiles overlap (I think DeepZoom format uses 4 for example?)

Thanks for any guidance!

Answer 1

The advantage is when using sub-pixeling and interpolation when the tiles are placed at non-integer values.

If they overlap a little (usually just a single pixel) they will camouflage the tiny gap that typically occur.

(right-click and select "view image" to see larger version)

^{(from this question)}

For performance one would tend to at least use width and height divisible by 4 (or 8 for 64-bit) as these are faster to copy in memory, and often a size of 2ⁿ (ie. 32, 64, 128 etc.). Also see mip-mapping for zooming.