[gdal-dev] Python WriteArray()

[Jay L.]

I am working on processing some raster images and have been really
struggling with processing times.  I have tracked the issue down to GDAL's
WriteArray() function.  I am cutting the image into blocks and processing in
small chunks.  This is facilitate working with really large images where the
entire array can not be loaded into memory.

If I try to call WriteArray() after processing each block processing time is
3+ hours for a 1GB image.  By loading the processed block (numpy arrays)
into a python list and then writing out a number at the same time I have cut
processing time to sub 2 minutes.

What is GDAL doing when it calls writeArray() that is requiring so much
time?  Has anyone else encountered this and been able to speed up GDAL's
array writing?

Thanks Jay

Here is an example is pseudocode:

open the raster

iterate through the bands using dataset.GetRasterBand(j)

iterate through the rows
    iterate through the columns

    readAsArray(a block of rows and columns)

    process the array in numpy

    #The more often this is called the slower the entire script runs...why?
    write out the array with outdataset.GetRasterBand(j).WriteArray(the
proper place to insert the modified array)
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