Comment 6 for bug 648379

Given the symptoms:

1) Occurs during resizing using factors that are not powers of 2 (i.e., 2, 4, 8, etc.). Comment #2
2) The thatched pattern is the color (254, 254, 254), where pure white is (255, 255, 255). Attachment to Comment #1
3) Only occurs for pure white (255, 255, 255) starting image. Comment #3

I would strongly suspect that this is not a bug, but a rounding error inherent in filter. It just happens that only images starting from pure white end up with rounding errors large enough to change a pixel value by one. The Lanczos filter actually takes on negative values at places, so that might be enough to put a resampled pixel one value below where it should be when the scaling isn't a nice power of 2.

In other words, this is a limitation of the filter, not a programming bug.