[3/5] windowscodecs: Create a predefined black&white palette if 1 bpp TIFF image doesn't have one.

[Vincent Povirk]

>> Are you sure about this? My understanding is that the result of
>> CopyPalette is unspecified when your pixel format is not an indexed
>> color format (in this case, a grayscale format).
>
> It seems that WIC always creates a predefined palette if an image doesn't
> have one, see the test sent in 2/5.

The test in 2/5 was for gdiplus, not WIC.

>> So, while it's not really a problem to do that (unless a program
>> relies on the exact behavior of this decoder, which seems unlikely),
>> for correctness you shouldn't ever be relying on this change.
>
> The problem is that gdiplus always expects a palette when converting
> between formats and crashes if there is no one.

Gdiplus can create its own grayscale palette for grayscale formats if
it needs one.