[Gdal-dev] Transparency in 8bit geotiffs with a color table
rayg at daylongraphics.com
Sun Oct 1 01:27:19 EDT 2006
As far as I understand the TIFF 6 spec:
Set SamplesPerPixel to 2, and BitsPerSample to [8 8], to store 8-bit
pixels with an 8-bit alpha mask.
If you're premultplying alpha into the palette's colors, set
ExtraSamples to 1, otherwise set it to 2.
After writing each pixel's value (the palette index), write its alpha value.
Hope this helps,
> I'm trying, without success, to create a geotiff, byte format, with
> entry of the
> color table as a transparent color (by playing with alpha), but
> keep on
> getting opaque images.
> Is there any way to get transparent output in 8bit geotiffs with a color
> Andrea Aime
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