IPP 5.2, using IppiResizeCenter_8u_C4R.The picture here shows the result of a slight stretching using Lanczos (left) and linear (right).
Looks like the Lanczos version exposes garbage for some near-white points, (no problem with white, more around 250/255 RGB values (same garbage for just one of the RGB components).
I know the text uses cleartype and I shouldn't expect the sub-pixel color trick to scale well, however this is toougly to be normal (I'd expect it to be more or less like the linear version).
I have checked that no premultiplied RGB was higher than the alpha. I also checked cubic interpolation, result is ok just like linear.
Sorry if I can't post the source bitmap, it's done by code and I have no code to save it in a format with alpha (yet).
Haven't checked yet if this was fixed in 5.3 or higher. Edit: still happens in version 6.0.
Ok so it's only if width or height is less than 6? I'm afraid my bitmap was bigger than that.
If you ask me, it looked pretty much like an overflow. The source bitmap had premultiplied alpha. You know the common saturated pixels effect when you try to blend a bitmap where the RGB's are higher than the alpha? It looked like that, like if the interpolated pixels were exceeding the alpha. I'll see if I can do it again & save a bitmap.