[gdal-dev] Modifying a raster pixel by pixel with GDAL

[Even Rouault]

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, ....)