[Gdal-dev] GDALWarp Gif Problems

Frank Warmerdam warmerdam at pobox.com
Tue Jan 23 20:46:20 EST 2007

Chris Portka wrote:
> Thanks for all your help so far.  I can now "successfully" warp without 
> an exception occurring.  However, now when I try to actually read the 
> data it is corrupted, or entirely blank (every pixel of the output file 
> is black).  I think I'm having a problem getting  all the bands copied 
> out of the raster file.  I want every band from the source raster to be 
> copied and transformed to the destination, is there an easy way to 
> specify this?  I'm also unclear on the type for the buffer I should be 
> passing to WarpRegionToBuffer - I'm assuming an nPixels * nLines * 
> nBands unsigned char array (the source raster is a 24-bit gif or jpg, so 
> nBands gives me 3).  Here's my code (I've labeled where the band code 
> starts):


The band selection logic seems ok.

>    GDALWarpOperation operation;
>    unsigned char *destination = (unsigned char *) new char[nPixels * 
> nLines * warpOptions->nBandCount];
>    operation.Initialize(warpOptions);
>    operation.WarpRegionToBuffer(0, 0, nPixels, nLines,    destination, 
> GDT_Unknown);

You should be passing GDT_Byte for pixel values that are unsigned
bytes (ie. unsigned char).   Hopefully this fixes things.

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org

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