Selon mathieu <[email protected]>: > Is there a simple way to find one or several pixel value none of the bands > use ?
Analyzing the histograms is the closest way I can think of. With "gdalinfo -hist in.tif" for example (but it is admitedly not completely trivial to find the index from the output) Or programatically with GetDefaultHistogram(): http://www.gdal.org/classGDALRasterBand.html#afeffe2ed8bfdc3d84200a57068ad0945 > > Mathieu > > 2015-01-14 12:06 GMT+01:00 Even Rouault-2 [via OSGeo.org] < > [email protected]>: > > > Selon mathieu <[hidden email] > > <http:///user/SendEmail.jtp?type=node&node=5181443&i=0>>: > > > > > The problem is that I don't know want an alpha channel because some of > > my > > > users work on MapInfo and MapInfo doesn't deal with alpha channels.. > > > > Really ??? Tell them to use QGIS instead. It does support alpha channel. > > > > Otherwise try to find a nodata value that isn't a valid pixel value. But > > I'd > > note that the nodata support in TIFF is a GDAL extended TIFF tag, so I > > wouldn't > > be surprised if MapInfo doesn't support it either. > > > > > > > > 2015-01-14 11:39 GMT+01:00 Even Rouault-2 [via OSGeo.org] < > > > [hidden email] <http:///user/SendEmail.jtp?type=node&node=5181443&i=1>>: > > > > > > > > > Mathieu, > > > > > > > > If 0 is a valid value at some locations of your raster, then you > > cannot > > > > use it > > > > as the nodata value. Use an alpha band instead for example by using > > > > -dstalpha > > > > instead of -dstnodata 0 > > > > > > > > Even > > > > > > > > > Hello, > > > > > > > > > > I crop a 3 band raster by a polygon with the following formula : > > > > > /gdalwarp -of GTiff -cutline polygon.shp -cl polygon input.tif > > > > output.tif > > > > > / > > > > > But pixels outside my polygon are assigned the 0 value. I'd like > > them to > > > > > have nodata > > > > > > > > > > If I put the -dstnodata 0 option : > > > > > /gdalwarp -of GTiff -cutline polygon.shp -cl polygon input.tif > > > > output.tif > > > > > -dstnodata 0/, all the pixels in each of the 3 bands that contain > > the 0 > > > > > value will be turned to nodata, even if they are contained in my > > > > polygon. > > > > > > > > > > Hence, 127 0 222 will become 127 nodata 222 > > > > > or 0 127 222 will become nodata 127 222 > > > > > > > > > > How to put the nodata value only outside my polygon ? > > > > > > > > > > Thanks a lot in advance ! > > > > > > > > > > Mathieu > > > > > > > > > > > > > > > > > > > > -- > > > > > View this message in context: > > > > > > > > > > > > > > > > > > > > > http://osgeo-org.1560.x6.nabble.com/Cropping-a-raster-by-a-polygon-only-nodata-outside-polygon-wanted-tp5181426.html > > > > > > > Sent from the GDAL - Dev mailing list archive at Nabble.com. > > > > > _______________________________________________ > > > > > gdal-dev mailing list > > > > > [hidden email] < > > http:///user/SendEmail.jtp?type=node&node=5181432&i=0> > > > > > http://lists.osgeo.org/mailman/listinfo/gdal-dev > > > > > > > > > > > > > > > > > -- > > > > Spatialys - Geospatial professional services > > > > http://www.spatialys.com > > > > _______________________________________________ > > > > gdal-dev mailing list > > > > [hidden email] <http:///user/SendEmail.jtp?type=node&node=5181432&i=1> > > > > > > http://lists.osgeo.org/mailman/listinfo/gdal-dev > > > > > > > > > > > > ------------------------------ > > > > If you reply to this email, your message will be added to the > > discussion > > > > below: > > > > > > > > > > > > > > > > http://osgeo-org.1560.x6.nabble.com/Cropping-a-raster-by-a-polygon-only-nodata-outside-polygon-wanted-tp5181426p5181432.html > > > > To unsubscribe from Cropping a raster by a polygon - only nodata > > outside > > > > polygon wanted, click here > > > > > > > > > < > > > > . > > > > NAML > > > > > > > > > < > > > http://osgeo-org.1560.x6.nabble.com/template/NamlServlet.jtp?macro=macro_viewer&id=instant_html%21nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify_subscribers%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_email%21nabble%3Aemail.naml> > > > > > > > > > > > > > > > > > > > > > -- > > > View this message in context: > > > > > > > > http://osgeo-org.1560.x6.nabble.com/Cropping-a-raster-by-a-polygon-only-nodata-outside-polygon-wanted-tp5181426p5181437.html > > > Sent from the GDAL - Dev mailing list archive at Nabble.com. > > > > > > -- > > Spatialys - Geospatial professional services > > http://www.spatialys.com > > _______________________________________________ > > gdal-dev mailing list > > [hidden email] <http:///user/SendEmail.jtp?type=node&node=5181443&i=2> > > http://lists.osgeo.org/mailman/listinfo/gdal-dev > > > > > > ------------------------------ > > If you reply to this email, your message will be added to the discussion > > below: > > > > > http://osgeo-org.1560.x6.nabble.com/Cropping-a-raster-by-a-polygon-only-nodata-outside-polygon-wanted-tp5181426p5181443.html > > To unsubscribe from Cropping a raster by a polygon - only nodata outside > > polygon wanted, click here > > > <http://osgeo-org.1560.x6.nabble.com/template/NamlServlet.jtp?macro=unsubscribe_by_code&node=5181426&code=bWF0aGlldS5yYWplcmlzb25AZ21haWwuY29tfDUxODE0MjZ8NTczODc4NDU1> > > . > > NAML > > > <http://osgeo-org.1560.x6.nabble.com/template/NamlServlet.jtp?macro=macro_viewer&id=instant_html%21nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify_subscribers%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_email%21nabble%3Aemail.naml> > > > > > > > -- > View this message in context: > http://osgeo-org.1560.x6.nabble.com/Cropping-a-raster-by-a-polygon-only-nodata-outside-polygon-wanted-tp5181426p5181453.html > Sent from the GDAL - Dev mailing list archive at Nabble.com. -- Spatialys - Geospatial professional services http://www.spatialys.com _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
