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

Dmitry Timoshkov dmitry at baikal.ru
Wed Jul 11 10:37:57 CDT 2012

Vincent Povirk <madewokherd at gmail.com> wrote:

> >> The test in 2/5 was for gdiplus, not WIC.
> >
> > My understanding is that gdiplus just reports what WIC returns in that regard,
> > and gdiplus doesn't generate fake palettes for real images (read: loaded from
> > a stream or a file).
> WIC did report a grayscale palette, implicitly in the pixel format. It
> doesn't need an explicit palette because it's not reporting an indexed
> color format.

A palette for 1 bpp format is optional.

> > Yes, but it should do that only for broken cases, when palette is not
> > provided with source data, like converting from indexed BitmapData in
> > GdipBitmapUnlockBits, or for idexed formats passed to GdipCreateBitmapFromScan0.
> I see no reason why gdiplus can't or shouldn't add a palette when
> converting from a WIC source with a grayscale image format to a
> gdiplus bitmap. If the resulting bitmap is indexed color, it probably
> should.

I think that's a job of WIC when it saves pixel data, gdiplus should create
a fake palette only for internal conversions, but even that job should be
done by a WIC pixel format converter.


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