Doesn't work with JPGs

[sionleroux]

Hi, the README says:

This tool supports only raster graphics.

All the examples show using PNGs but I thought I'd try a JPG and it crashes the program:

hexsticker dp.jpg 
INFO:hexsticker.create:Writing output to 'dp-sticker.jpg'
Traceback (most recent call last):
  File "/usr/lib/python3.10/site-packages/PIL/JpegImagePlugin.py", line 643, in _save
    rawmode = RAWMODE[im.mode]
KeyError: 'RGBA'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/lib/python3.10/site-packages/hexsticker/create.py", line 206, in create_hexsticker
    img.save(output_file, output_file_type.upper())
  File "/usr/lib/python3.10/site-packages/PIL/Image.py", line 2431, in save
    save_handler(self, fp, filename)
  File "/usr/lib/python3.10/site-packages/PIL/JpegImagePlugin.py", line 646, in _save
    raise OSError(msg) from e
OSError: cannot write mode RGBA as JPEG

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/bin/hexsticker", line 33, in <module>
    sys.exit(load_entry_point('hexsticker==1.2.0', 'console_scripts', 'hexsticker')())
  File "/usr/lib/python3.10/site-packages/click/core.py", line 1130, in __call__
    return self.main(*args, **kwargs)
  File "/usr/lib/python3.10/site-packages/click/core.py", line 1055, in main
    rv = self.invoke(ctx)
  File "/usr/lib/python3.10/site-packages/click/core.py", line 1404, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/lib/python3.10/site-packages/click/core.py", line 760, in invoke
    return __callback(*args, **kwargs)
  File "/usr/lib/python3.10/site-packages/hexsticker/cli.py", line 69, in hexsticker
    create_hexsticker(**options)
  File "/usr/lib/python3.10/site-packages/hexsticker/create.py", line 208, in create_hexsticker
    raise exceptions.SaveError(f"Failed to save resulting image: {str(exc)}") from exc
hexsticker.exception.SaveError: Failed to save resulting image: cannot write mode RGBA as JPEG

Have I made a mistake, e.g. missed installing a library? Or does the program not support JPEG? I'd guess the latter because the stack trace mentions saving RGBA as JPEG, and I suppose the A in RGBA is because of the transparent background after the hexagon is cut out and JPEGs don't support transparency. Maybe it would be good to add a file type check at the beginning of the program to make sure the user provides an input filetype that will support transparency in the output?

[fridex]

Hi @sinisterstuf, thanks for the report. Yes, JPEG is not supported. +1 on the filetype check. Would you mind submitting a PR for this? Thank you.

[sionleroux]

Sure, I'm pretty unfamiliar with any of these libraries but I'll give it a go!

[sionleroux]

Ok I checked the code a bit today and this crash is caused by this commit a0a9869 which changed the image mode from RGB to RGBA seemingly without consideration for the fact that only 3 out of 6 of the supported filetypes can handle transparency. I think it would be lame to revert this to its previous value because having transparent backgrounds is useful when possible.

Instead I intend to check whether the output file format supports transparency or not, and convert it to non-transparent RGB if necessary. This will involve some changes because it seems right now we only check the filetypes are valid for the input file. So:

• Add a 2nd list of file types for only those that support transparency
• Extract the filetype checking code to a smaller function (although maybe it's enough to add a condition inside the extension checking function and use that instead)
• Use RGB if the file format doesn't support transparency
• Maybe raise an exception if the input file would support transparency but the output file has been specified explicitly with -o and it does not support transparency, haven't decided yet if this is better to force it to non-transparent
• Change the default background colour from transparent red to transparent white

[fridex]

What about providing an option for this so users can control behaviour and raise an exception for unsupported combinations?