Daniel, You can build your own colour table using the api. In not familiar with the C# interface but for C, you can refer to http://gdal.org/classGDALColorTable.html
-- Best regards, Chaitanya Kumar CH On 25-Feb-2014 8:58 pm, "windchaser" <[email protected]> wrote: > Chaitanya, > > Thanks for your prompt reply. I think I would like to use display engine, > but I am still trying to figure out which function I need to use to 'load a > different color table'. I am using GDAL with C# in a VS2010 project. Below > is the function that opens the raster text file and returns the bitmap. > > when trying to retrieve the color table using this statement "ColorTable > ct = band.GetRasterColorTable();" the color table returned is empty. > > From your post I understand that a VRT dataset needs to be created by > copying the source dataset and then this VRT dataset can be manipulated to > add more classes apply a color gradient to the classes. > > Are there any C# examples of using VRT dataset? > Could you highlight the main steps that I need to take in order to achieve > this? > > Thanks, > > public static Bitmap GetBitmap(string sFileName) > { > //**How to write manipulated raster values to ASCII grid with GDAL? > //** > http://stackoverflow.com/questions/10635107/how-to-write-manipulated-raster-values-to-ascii-grid-with-gdal > OSGeo.GDAL.Dataset ds = Gdal.Open(sFileName, > OSGeo.GDAL.Access.GA_ReadOnly); > if (ds == null) > { > MessageBox.Show("Invalid File Format!"); > return null; > } > > OSGeo.GDAL.Driver dr = ds.GetDriver(); > > int nWidth = ds.RasterXSize; > int nHeight = ds.RasterYSize; > > //** GDAL CSharp Guide gdal - Revision 26980: > /trunk/gdal/swig/csharp/apps > //** http://svn.osgeo.org/gdal/trunk/gdal/swig/csharp/apps/ > > // Creating a Bitmap to store the GDAL image in > Bitmap bitmap = new Bitmap(nWidth, nHeight, > PixelFormat.Format8bppIndexed); > // Obtaining the bitmap buffer > BitmapData bitmapData = bitmap.LockBits(new Rectangle(0, 0, > nWidth, nHeight), ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed); > try > { > int stride = bitmapData.Stride; > IntPtr buf = bitmapData.Scan0; > Band band = ds.GetRasterBand(1); > band.ReadRaster(0, 0, nWidth, nHeight, buf, nWidth, nHeight, > DataType.GDT_Byte, 1, stride); > } > finally > { > bitmap.UnlockBits(bitmapData); > } > > return bitmap; > } > > > > *Daniel* > c: 1 (705) 499-2450 > > > On Tue, Feb 25, 2014 at 12:01 AM, chaitanya_ch [via OSGeo.org] <[hidden > email] <http://user/SendEmail.jtp?type=node&node=5105844&i=0>> wrote: > >> Daniel, >> >> You can make changes in two places. In the data or the display engine. In >> the data, you can modify the colour table. This will be permanent. In the >> display, you just load a different color table based on the table of pixel >> values. If you don't like either, you can build a gdal vrt file and modify >> its colour table. >> >> http://www.gdal.org/gdalbuildvrt.html >> http://www.gdal.org/gdal_vrttut.html >> >> -- >> Best regards, >> Chaitanya Kumar CH >> On 25-Feb-2014 9:26 am, "windchaser" <[hidden >> email]<http://user/SendEmail.jtp?type=node&node=5105703&i=0>> >> wrote: >> >>> Hi, >>> I am working with GDAL in a C# project. I need help figuring out how to >>> increase the colors displayed on a raster grid. Opening the file using >>> Gdal.Open("myfile", OSGeo.GDAL.Access.GA_ReadOnly); seems to offer some >>> colors but I would like to increase the number of colors for the raster >>> map, >>> specially for floating point raster. >>> >>> Here is an example of what i am trying to achieve using GDAL. >>> >>> http://screencast.com/t/LPjJ7pTk <http://screencast.com/t/LPjJ7pTk> >>> >>> Thanks for your help! >>> >>> Daniel >>> >>> >>> >>> -- >>> View this message in context: >>> http://osgeo-org.1560.x6.nabble.com/Help-with-color-map-for-raster-grid-tp5105698.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=5105703&i=1> >>> http://lists.osgeo.org/mailman/listinfo/gdal-dev >>> >> >> _______________________________________________ >> gdal-dev mailing list >> [hidden email] <http://user/SendEmail.jtp?type=node&node=5105703&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/Help-with-color-map-for-raster-grid-tp5105698p5105703.html >> To unsubscribe from Help with color map for raster grid, 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: Re: Help with color map for raster > grid<http://osgeo-org.1560.x6.nabble.com/Help-with-color-map-for-raster-grid-tp5105698p5105844.html> > Sent from the GDAL - Dev mailing list > archive<http://osgeo-org.1560.x6.nabble.com/GDAL-Dev-f3742093.html>at > Nabble.com. > > _______________________________________________ > gdal-dev mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/gdal-dev >
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