[gdal-dev] GDAL appears to ignore NoDataValue

[Ophir Yoktan]

Thanks! it works

a follow up "bonus" question
I get the same problem when trying to create a mosaic by warping to images
to a new dataset.

my code is basically copied from the "GDAL Warp API Tutorial" page
http://www.gdal.org/warptut.html

and adding:
psWarpOptions->padfSrcNoDataReal = new double(0);
 On Feb 29, 2012 11:03 AM, "Even Rouault" <even.rouault at mines-paris.org>
wrote:

> Selon Ophir Yoktan <ophiry at gmail.com>:
>
> Several errors :
> 1) The NoDataValue and HideNoDataValue elements are only valid under the
> VRTRasterBand element, not SimpleSource
> 2) You want to change SimpleSource to ComplexSource, and add a
> <NODATA>0</NODATA> element in it. (well basically rename your current
> NoDataValue to NODATA.
>
>
> > I'm trying to build a mosaic, and I rely on the NoDataValue feature to
> > treat some parts of the image as transparent.
> > However, it appears that GDAL doesn't work as expected.
> >
> > I also created a very simple test case using a vrt dataset and
> > gdal_translate - and I get the same results (that is - the 2nd image
> draws
> > over the 1st image, ignoring "transparent areas")
> >
> > I have to 100X100 image files with a white marking (different in each
> file)
> > over black background (black being exactly equal to 0)
> > I built a simple vrt file:
> >
> >     <VRTDataset rasterXSize="100" rasterYSize="100">
> >       <VRTRasterBand dataType="Byte" band="1">
> >         <ColorInterp>Gray</ColorInterp>
> >         <SimpleSource>
> >           <SourceFilename relativeToVRT="1">a1.tif</SourceFilename>
> >           <SourceBand>1</SourceBand>
> >           <SrcRect xOff="0" yOff="0" xSize="100" ySize="100"/>
> >           <DstRect xOff="0" yOff="0" xSize="100" ySize="100"/>
> >       <HideNoDataValue>1</HideNoDataValue>
> >       <NoDataValue>0</NoDataValue>
> >         </SimpleSource>
> >         <SimpleSource>
> >           <SourceFilename relativeToVRT="1">a2.tif</SourceFilename>
> >           <SourceBand>1</SourceBand>
> >           <SrcRect xOff="0" yOff="0" xSize="100" ySize="100"/>
> >           <DstRect xOff="0" yOff="0" xSize="100" ySize="100"/>
> >       <HideNoDataValue>1</HideNoDataValue>
> >       <NoDataValue>0</NoDataValue>
> >         </SimpleSource>
> >       </VRTRasterBand>
> >     </VRTDataset>
> > and I run the command:
> >
> >     gdal_translate mosaic.vrt mosaic.tif
> >
> > The result is identical to image `a2.tif`, instead of being a combination
> > of `a1.tif` and `a2.tif`
> >
> > I got the error using gdal 1.8 and 1.9
> >
> > any ideas?
> >
>
>
>
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