Chris,
ReadAsArray() returns a NumPy array, and the first dimension in NumPy is
the slowest varying one, that is y.
GDAL's geotransform is
Xgeoref = gt[0] + column * gt[1] + line * gt[2]
Ygeoref = gt[3] + column * gt[4] + line * gt[5]
and GDAL's Raster API have their arguments with column first, line second.
So, there's no transposition. It is just a different convention on how
to present dimensions.
Note: if you used GDAL's multidimensional API, it would be similar to
NumPy convention, with slowest varying dimension being the first index
value.
Even
Le 04/12/2022 à 09:02, Chris Crook a écrit :
Hi
I am using the Python GDAL API and looking at a simple TIFF image with
a test program:
from osgeo import gdal
dataset = gdal.Open('test-gdal.tif')
transform=dataset.GetGeoTransform()
nx=dataset.RasterXSize
ny=dataset.RasterYSize
data=dataset.ReadAsArray()
print(f"Raster xsize, ysize ({nx},{ny})")
print(f"ReadAsArray dimensions {data.shape}")
print(f"GeoTransform: {transform}")
The output is:
test_python_api.py
Raster xsize, ysize (3,4)
ReadAsArray dimensions (4, 3)
GeoTransform: (22.15, 0.7, 0.0, -69.5, 0.0, 1.0)
I am confused that the array appears transposed from the raster x,y size.
Is this always the cased. As far as I can tell the geotransform is
assuming x,y (0-2,0-3 values) to map indices to location, which is
what I want to do.
Can I assume that the array is always transposed? Or if not how do I
identify when this is the case?
Many thanks in advance
Chris Crook
Land Information New Zealand
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