Dear Gdal-Team and List,
At first I want to thank you for the great work you guys are doing with GDAL. I really enjoy using this tools. I am especially doing rectification of unreferenced raster images with the gdal tools. At the beginning I did the rectification with the gdal_translate and gdalwarp tools. This works pretty well and allowed me to use different order polynomials and a plate spline transformer for my image transformation. Also it was possible for me to use different resampling algorithm for my images. The problem was that I always had to clip the input image (using pixel coordinates) first, save the result in a temporally dataset - first I/O process - and doing than the transformation using gdal_translate (add gcps) and gdalwarp (transformation and resampling) - second I/O process. In my use case the most time the processes spent was for the I/O operations. So I decided to use the python-bindings for processing, in hoping to do some operations in memory. This works great for doing a affine transformation (dataset.SetGeotransform) without resampling and gave a big performance improvement. The improvement came through reading the file once in memory, doing there the clipping and adding of the transformation matrix and then writing this to disk. So I got only once to read the image from the disk and once to write the clipped image, together with the transformation matrix, back to disk. But I couldn't figure out how to do for example a plate spline transformation or an order 2 polynomial transformation. After further investigation it seems like this is not possible with the python bindings, are I am right with this? Also it seems that the python bindings doesn't allow to do a resampling of an image without using the gdal.ReprojectImage method, what from my understand would make sense in my case or? Hope I make my questions clear and somebody could give me some feedback. Kind regards, JM
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