NoData may remain opaque in WMS requests against a paletted tiff
Description
One palette entry is marked as nodata in the source image, during color expansion the nodata is either lost, or mixed with other valid entries sharing the same target color. Various cases to consider:
Direct raster rendering
Standard rendering And orthogonally:
transparent output,
fixed background opaque output Also consider cases in which the nodata palette entry is mapped to black, but another valid entry in the same palette also maps to black (the expansion must not confuse the two cases).
Medium
One palette entry is marked as nodata in the source image, during color expansion the nodata is either lost, or mixed with other valid entries sharing the same target color.
Various cases to consider:
Direct raster rendering
Standard rendering
And orthogonally:
transparent output,
fixed background opaque output
Also consider cases in which the nodata palette entry is mapped to black, but another valid entry in the same palette also maps to black (the expansion must not confuse the two cases).