Bilinear interpolation breaks fg-bg separation

[jwilk]

Poppler can use bilinear interpolation even when the Interpolate flag is not enabled.
For black&white images that don't have the scaling factor exactly right, this can introduce a lot of gray pixels, breaking the foreground-background separation.
It would be great if we could implement some work-around for this.

Bug reports:

• https://bugs.debian.org/760396
• https://bugs.debian.org/764458
• https://bugs.freedesktop.org/show_bug.cgi?id=68360

Relevant Poppler commits:

• 7248da095f67d57c ("Use Interpolate flag to decide whether applying image interpolation during rendering; Fixes bug #9860")
• a97aead193a927b9 ("Splash: Implement bilinear image scaling; Bug #22138")