full list of simple_image image types

[raybellwaves]

Curious how easy (hard) it would be to add the full list of image types that simple_image provides.

When running

from satpy import available_writers
available_writers()

I see ['mitiff', 'cf', 'simple_image', 'geotiff', 'scmi']. I believe what I was after was as a list of image formats I can provide when using scn.save_dataset e.g. png as doing scn2.save_dataset('true_color', filename='test') returns

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
~/local/bin/anaconda3/envs/dev/lib/python3.8/site-packages/trollimage/image.py in check_image_format(fformat)
     81     try:
---> 82         fformat = cases[fformat]
     83     except KeyError:

KeyError: ''

During handling of the above exception, another exception occurred:

UnknownImageFormat                        Traceback (most recent call last)
<ipython-input-12-7b813b2b856c> in <module>
      1 #scn2.show('true_color')
----> 2 scn2.save_dataset('true_color', filename='test')

~/local/bin/anaconda3/envs/dev/lib/python3.8/site-packages/satpy/scene.py in save_dataset(self, dataset_id, filename, writer, overlay, decorate, compute, **kwargs)
   1302                                           filename=filename,
   1303                                           **kwargs)
-> 1304         return writer.save_dataset(self[dataset_id],
   1305                                    overlay=overlay, decorate=decorate,
   1306                                    compute=compute, **save_kwargs)

~/local/bin/anaconda3/envs/dev/lib/python3.8/site-packages/satpy/writers/__init__.py in save_dataset(self, dataset, filename, fill_value, overlay, decorate, compute, **kwargs)
    827         img = get_enhanced_image(dataset.squeeze(), enhance=self.enhancer, overlay=overlay,
    828                                  decorate=decorate, fill_value=fill_value)
--> 829         return self.save_image(img, filename=filename, compute=compute, fill_value=fill_value, **kwargs)
    830 
    831     def save_image(self, img, filename=None, compute=True, **kwargs):

~/local/bin/anaconda3/envs/dev/lib/python3.8/site-packages/satpy/writers/simple_image.py in save_image(self, img, filename, compute, **kwargs)
     63 
     64         LOG.debug("Saving to image: %s", filename)
---> 65         return img.save(filename, compute=compute, **kwargs)

~/local/bin/anaconda3/envs/dev/lib/python3.8/site-packages/trollimage/xrimage.py in save(self, filename, fformat, fill_value, compute, keep_palette, cmap, **format_kwargs)
    422                                  **format_kwargs)
    423         else:
--> 424             return self.pil_save(filename, fformat, fill_value,
    425                                  compute=compute, **format_kwargs)
    426 

~/local/bin/anaconda3/envs/dev/lib/python3.8/site-packages/trollimage/xrimage.py in pil_save(self, filename, fformat, fill_value, compute, **format_kwargs)
    608         """
    609         fformat = fformat or os.path.splitext(filename)[1][1:]
--> 610         fformat = check_image_format(fformat)
    611 
    612         if fformat == 'png':

~/local/bin/anaconda3/envs/dev/lib/python3.8/site-packages/trollimage/image.py in check_image_format(fformat)
     82         fformat = cases[fformat]
     83     except KeyError:
---> 84         raise UnknownImageFormat("Unknown image format '%s'." % fformat)
     85     return fformat
     86 

UnknownImageFormat: Unknown image format ''.

In that error message I saw if fformat == 'png' so I ended up going for that first time round.

[djhoese]

Very good points. The issue for why this doesn't exist is that these available formats come from PIL (the python image library) and I think what formats can be used inevitably depend on how your installed version of PIL was built. @mraspaud maybe we could provide some of the standard ones and then link to PIL's documentation? Or maybe PIL has a way of listing them?

[djhoese]

Based on this page we should probably just list jpeg and png and then link to the page: https://pillow.readthedocs.io/en/stable/handbook/image-file-formats.html

[mraspaud]

Closed through pytroll/trollimage#88