Perhaps this helps. Good luck. //Anders Söderman Sweden
http://www.gdal.org/frmt_gtiff.html Internal nodata masks (from GDAL 1.6.0) TIFF files can contain internal transparency masks. The GeoTIFF driver recognizes an internal directory as being a transparency mask when the FILETYPE_MASK bit value is set on the TIFFTAG_SUBFILETYPE tag. According to the TIFF specification, such internal transparency masks contain 1 sample of 1-bit data. Although the TIFF specification allows for higher resolutions for the internal transparency mask, the GeoTIFF driver only supports internal transparency masks of the same dimensions as the main image. Transparency masks of internal overviews are also supported When the GDAL_TIFF_INTERNAL_MASK environment variable is set to YES and the GeoTIFF file is opened in update mode, the CreateMaskBand() method on a TIFF dataset or rasterband will create an internal transparency mask. Otherwise, the default behaviour of nodata mask creation will be used, that is to say the creation of a .msk file, as per RFC 15 _____ From: qgis-user-boun...@lists.osgeo.org [mailto:qgis-user-boun...@lists.osgeo.org] On Behalf Of Pietro Panzeri Sent: den 3 juni 2010 12:57 To: qgis-user@lists.osgeo.org Subject: [Qgis-user] Re: Grayscale GeoTiff and transparency using GDAL. No one has a solution? Thank you. On Mon, May 31, 2010 at 10:42 AM, Pietro Panzeri <pietro.panz...@treuropa.com> wrote: Hi all, I'm writing a plugin using GDAL C library to allow the user to create a grayscale GeoTiff with transparency. I've used the following code to init the raster: Driver = GDALGetDriverByName("GTiff"); papszOptions = CSLSetNameValue(papszOptions, "COMPRESS", "LZW"); Dataset = GDALCreate(Driver, SrcFilename, XSize, YSize, 2, GDT_Byte, papszOptions); Band1 = GDALGetRasterBand(Dataset, 1); GDALSetRasterColorInterpretation(Band1, GCI_GrayIndex); Band2 = GDALGetRasterBand(Dataset, 2); GDALSetRasterColorInterpretation(Band2, GCI_AlphaBand); ... Init the two bands ... The result is a correct grayscale image but without transparency. Can someone point me a way to create a grayscale GeoTiff with a transparency? Thank you very much. Pietro -- Pietro Panzeri Software Development Manager Tele-Rilevamento Europa - T.R.E. srl Via Vittoria Colonna, 7 20149 Milano Italia Tel.: +39.02.4343.121 - Fax: +39.02.4343.1230 pietro.panz...@treuropa.com - www.treuropa.com -- Pietro Panzeri Software Development Manager Tele-Rilevamento Europa - T.R.E. srl Via Vittoria Colonna, 7 20149 Milano Italia Tel.: +39.02.4343.121 - Fax: +39.02.4343.1230 pietro.panz...@treuropa.com - www.treuropa.com
_______________________________________________ Qgis-user mailing list Qgis-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-user
