The error regarding the file extension has been handled, you either use `BMP`

(without the dot) or pass the output name with the extension already. Now to handle the error you need to properly modify your data in the frequency domain to be saved as an integer image, `PIL`

is telling you that it doesn’t accept float data to save as BMP.

Here is a suggestion (with other minor modifications, like using `fftshift`

and `numpy.array`

instead of `numpy.asarray`

) for doing the conversion for proper visualization:

```
import sys
import numpy
from PIL import Image
img = Image.open(sys.argv[1]).convert('L')
im = numpy.array(img)
fft_mag = numpy.abs(numpy.fft.fftshift(numpy.fft.fft2(im)))
visual = numpy.log(fft_mag)
visual = (visual - visual.min()) / (visual.max() - visual.min())
result = Image.fromarray((visual * 255).astype(numpy.uint8))
result.save('out.bmp')
```