[gdal-dev] Modifying a raster pixel by pixel with GDAL
Hello, I want to modify every single pixel of a 1 band GeoTiff file, following a formula (multiply each pixel for a value and then add another value). output_pixel[i][j] = input_pixel[i][j] * K[i][j] + C[i][j] I can't apply a linear scale (it would be as easier as -scale option in gdal_translate). Sounds more like applying a mask to the band's data. My first approach is to get every data block of the raster (IReadBlock call), apply the transformation to every single pixel ( = apply a mask to the data block), and put the block in the output raster. Is there any other faster/smarter approach? Many thanks in advance, -- Jorge Arevalo http://www.krop.com/jorgearevalo ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] Modifying a raster pixel by pixel with GDAL
Le jeudi 13 décembre 2012 19:58:50, Jorge Arevalo a écrit : > Hello, > > I want to modify every single pixel of a 1 band GeoTiff file, > following a formula (multiply each pixel for a value and then add > another value). > > output_pixel[i][j] = input_pixel[i][j] * K[i][j] + C[i][j] > > I can't apply a linear scale (it would be as easier as -scale option > in gdal_translate). Sounds more like applying a mask to the band's > data. > > My first approach is to get every data block of the raster (IReadBlock > call), apply the transformation to every single pixel ( = apply a mask > to the data block), and put the block in the output raster. > > Is there any other faster/smarter approach? I would follow exactly the same approach. If you don't do in-place update, be carefull that the source and target rasters have exactly the same block size and data type if you want to use directly ReadBlock() / WriteBlock(). If not, you must use ReadBlock() / RasterIO(GF_Write, ) ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
Re: [gdal-dev] Modifying a raster pixel by pixel with GDAL
Thanks for the response and the wise advice, Even. I'll do it in that way. On Thu, Dec 13, 2012 at 8:06 PM, Even Rouault wrote: > Le jeudi 13 décembre 2012 19:58:50, Jorge Arevalo a écrit : >> Hello, >> >> I want to modify every single pixel of a 1 band GeoTiff file, >> following a formula (multiply each pixel for a value and then add >> another value). >> >> output_pixel[i][j] = input_pixel[i][j] * K[i][j] + C[i][j] >> >> I can't apply a linear scale (it would be as easier as -scale option >> in gdal_translate). Sounds more like applying a mask to the band's >> data. >> >> My first approach is to get every data block of the raster (IReadBlock >> call), apply the transformation to every single pixel ( = apply a mask >> to the data block), and put the block in the output raster. >> >> Is there any other faster/smarter approach? > > I would follow exactly the same approach. If you don't do in-place update, be > carefull that the source and target rasters have exactly the same block size > and data type if you want to use directly ReadBlock() / WriteBlock(). If not, > you must use ReadBlock() / RasterIO(GF_Write, ) -- Jorge Arevalo http://www.krop.com/jorgearevalo ___ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
