[Poppler-bugs] [Bug 31926] pdftops-0.15.2 -level1sep inverts the image mask polarity

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=31926

--- Comment #45 from William Bader <williambader at hotmail.com> 2011-02-01 17:40:41 PST ---
Created an attachment (id=42845)
 --> (https://bugs.freedesktop.org/attachment.cgi?id=42845)
Three images of bug-poppler27482-precision.pdf

I think that the rasterization is necessary.  Without the rasterization, the
mask becomes a solid black block.  In some cases, the image looks reasonable
with the mask solid white or black, but in general it does not work.

I have attached close-ups of three versions of the image of bug-poppler27482
using gv + gs 9.01.
The first is a view of the ps generated by pdftops-0.16.2 + the precision patch
with -level1 bug-poppler27482.pdf
The second is a view of the ps generated by pdftops-0.16.2 + the precision
patch + the level1bug rasterization patch with -level1 on bug-poppler27482.pdf.
The third is a view of the original pdf.

I circled a part of the shadow at the upper right of the "S" in the word
"Samstag" (at the upper left of the full image).
In the first image, without the level1bug patch, the shadow is solid black.
In the second image, with the level1bug patch, and in the third image, the
shadow is shaded.
The same difference between solid black and gray scaled shading happens in
other places, for example, at the bottoms of the letters.

The solid black without the level1bug patch is wrong.  It is barely visible in
this image, but it ruins the image in other files, like the faces at the bottom
of the testimagemask.pdf file attached to
https://bugs.freedesktop.org/show_bug.cgi?id=22216 .  In this file, three of
the faces are gray scaled through a mask, and without the level1bug patch,
those faces become black like the background.

The second image in the triplet shows why the level1bug patch should be
followed with another patch that makes the resolution settable.  The
rasterization is currently hard-coded to 300 dpi which is good enough for
pictures but a little low for text.  I am still planning on doing it.

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