[gdal-dev] Setting the noData flag in a GeoTIFF

[Jukka Rahkonen]

Jonathan Moules <jonathanmoules <at> warwickshire.gov.uk> writes:

> 
> 
> 
> Hi Even,
> That worked great.
> It figures that I'd tried about 6 different permutations, including a few
without "-hidenodata"; but none of them was the right one it seems.
> 
> 
> It's no problem recreating the tifs as they're small test tifs that takes
a few seconds to process.
> 
> Many thanks!Jonathan

Hi,

Be warned that the result may not be what you believe. You are compressing
to jpeg and as a lossy method it does not store constant pixel values for
the whole nodata area. If 255-255-255 pixels are nodata values you will get
also pixels like 255-255-254 here and there and they will not be transparent
in applications. That may not be a problem for you if you combine
rectangular images with full of data into a mosaic but if you warp images
one by one into another projection so that they will get rotated and then
want to use the warped images side by side you would see that the
overlapping areas look bad.

-Jukka Rahkonen-