[Poppler-bugs] [Bug 70259] New: Transparent grid visible through type 1 shading

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=70259

          Priority: medium
            Bug ID: 70259
          Assignee: poppler-bugs at lists.freedesktop.org
           Summary: Transparent grid visible through type 1 shading
          Severity: normal
    Classification: Unclassified
                OS: Linux (All)
          Reporter: obscurans at gmail.com
          Hardware: Other
            Status: NEW
           Version: unspecified
         Component: cairo backend
           Product: poppler

Created attachment 87261
  --> https://bugs.freedesktop.org/attachment.cgi?id=87261&action=edit
Minimal PDF with type 1 shading

When displaying a Type 1 shading object in evince, poppler 0.20.4 displays a
prominent grid of transparent color between what looks to be the sampling grid.
This does not improve when scaling up, and from anti-aliasing looks even worse
when scaled down.

Also, the resolution of the sampling grid seems to be fixed, regardless of the
MediaBox/Matrix scaled size of the shading and the scaling factor. gs displays
it properly.

I am no expert at all, but I thought the main point of a Type 1 shading was
that it is defined at arbitrary points. So the simplest and most correct way of
rendering it would be to directly transform the screen pixel to user/pattern
space coordinates and invoke the supplied function on each pixel.

This would cause a recompute only on a resizing event, which is in line with
everything else. As to anti-aliasing, it is a specifiable property of the
shading dictionary, default false.

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