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<font face="Times New Roman, Times, serif">Hi all,<br>
<br>
What is the relationship between the "PER_DATASET_ALPHA" mask of
the RGB bands in a raster dataset, and the Alpha Channel? I
created a four-band tiff file </font><font face="Times New Roman,
Times, serif"> with gdalwarp </font><font face="Times New Roman,
Times, serif">from an RGB original. On creation, the fourth band
has all values set to 255, and the whole picture is visible.
However, when setting parts of the fourth band to zero with
gdal_rasterize, everything remains visible. Could that be caused
by the Mask Flags of the first three channels, and, if so, what
can I do about it? <br>
<br>
Band 1 Block=4016x1 Type=Byte, ColorInterp=Red<br>
Mask Flags: PER_DATASET ALPHA <br>
Band 2 Block=4016x1 Type=Byte, ColorInterp=Green<br>
Mask Flags: PER_DATASET ALPHA <br>
Band 3 Block=4016x1 Type=Byte, ColorInterp=Blue<br>
Mask Flags: PER_DATASET ALPHA <br>
Band 4 Block=4016x1 Type=Byte, ColorInterp=Alpha<br>
<br>
Jan</font><br>
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