DdsImagePlugin fails when dxgi_format == DXGI_FORMAT_BC7_UNORM_SRGB

[ouroborus]

Pillow/src/PIL/DdsImagePlugin.py

Lines 156 to 159 in 84fed4d

	elif dxgi_format == DXGI_FORMAT_BC7_UNORM_SRGB:
	self.pixel_format = "BC7"
	self.im_info["gamma"] = 1 / 2.2
	n = 7

At self.im_info["gamma"] = 1 / 2.2, self.im_info has never been initialized and so trying to set self.im_info["gamma"] fails with:

AttributeError: 'DdsImageFile' object has no attribute 'im_info'

As far as I can tell, this is the only place im_info is ever referenced in this or the ancestor classes.

A possible solution would be to change this section to:

                elif dxgi_format == DXGI_FORMAT_BC7_UNORM_SRGB:
                    self.pixel_format = "BC7"
                    if not hasattr(self, 'im_info'):
                        self.im_info = {}
                    self.im_info["gamma"] = 1 / 2.2
                    n = 7

An alternate solution would be to initialize im_info earlier in the loader method.

[radarhere]

Can you provide an image that demonstrates the problem? Ideally, one that can be included as part of the test suite and distributed under the Pillow license?

[ouroborus]

@radarhere None of the images I'm working with are available for that and I don't have a way to generate a new file. I'll see what I can do, but you shouldn't get your hopes up.

[ouroborus]

@radarhere In a rare alignment of fortune, I was able to produce a file that triggers this issue. See contents of DXGI_FORMAT_BC7_UNORM_SRGB.zip
.

[radarhere]

Thanks. My conclusion would be that it should be self.info rather than self.im_info - I've created PR #4171 with this solution.