without the try: and raise ValueError in the freeimage_plugin.py it returns:<br><br>Traceback (most recent call last):<br>&nbsp; File "G:\Marwen\Summer.py", line 61, in &lt;module&gt;io.imsave("test.tif",summation, plugin="freeimage")<br>&nbsp; File "C:\Python27\lib\site-packages\skimage\io\_io.py", line 129, in imsave return call_plugin('imsave', fname, arr, plugin=plugin, **plugin_args)<br>&nbsp; File "C:\Python27\lib\site-packages\skimage\io\_plugins\plugin.py", line 88, in call return func(*args, **kwargs)<br>&nbsp; File "C:\Python27\lib\site-packages\skimage\io\_plugins\freeimage_plugin.py", line 669, in imsave write(img, filename)<br>&nbsp; File "C:\Python27\lib\site-packages\skimage\io\_plugins\freeimage_plugin.py", line 538, in write bitmap, fi_type = _array_to_bitmap(array)<br>&nbsp; File "C:\Python27\lib\site-packages\skimage\io\_plugins\freeimage_plugin.py", line 601, in _array_to_bitmap fi_type = FI_TYPES.fi_types[(dtype.type, n_channels)]<br>KeyError: (&lt;type 'numpy.int32'&gt;, 1)<br><br>I'm afraid that is all I can do with my limited skills...<br>