[poppler] What about Bug +3307 now?

Tobias Wolf towolf at gmail.com
Thu Aug 13 16:31:30 PDT 2009

On Fr, 2009-08-14 at 00:22 +0200, Albert Astals Cid wrote:
> A Dijous, 13 d'agost de 2009, Tobias Wolf va escriure:

> > The merit can only be seen by looking at many PDFs at several zoom
> > levels. Especially small text is much more readable.
> >
> > But here is one striking example from the bug report:
> > https://bugs.freedesktop.org/attachment.cgi?id=19607
> > (top is current state, middle is the goal)
> I see almost no difference between top and middle, i'm sorry.

I find that hard to believe. Let me explain what you should see. So we
are on the same page. Also, please make sure you view the image on an
LCD not a CRT.

- Only the black text differs, the red text is annotation
- The first criterion is contrast. How sharp are the edges?

  * The horizontal arms and serifs are much sharper. Examples: « E,T »
    This is due to HINT_SLIGHT (hinting only in y-axis, doesn’t affect

  * Diagonal strokes are less coarse. Examples: « X,N »
  * Round bowls are sharper: Examples: « C,o,0,8 »
  * These two are better thanks to LCD filtering courtesy of FreeType.

- The second criterion is how well the letter shapes are preserved. 
  You cannot see that in this example. Monochrome text has 100% 
  contrast, but the shapes are poor in monochrome. It’s a trade-off 
  with a sweet spot.

> > Please give guidance how to proceed.
> If there is anything that needs to be patched in poppler, give us patches that 
> someone can understand and apply, we hardly reject patches, the problem is 
> that there's not much people "reviewing" patches because there's not much 
> people at all contributing to poppler. 

In many distros there is at least a community effort to keep Poppler
patched to provide this. This is because people notice.

The most complete patch I found is at [1]. I don’t really understand it,
and I don’t know who wrote it and AFAIK it wasn’t even submitted to this
list. Also it seems to not work together with the most recent Evince.
Although, it works via PyPoppler, according to my tests.

Myself, I have been using the patches attached to the bug I’m talking
about. But they apply in part to Poppler and in part to Evince. And in
the last iteration of Evince they stopped working most of the time.

Just google "+poppler +subpixel". There is genuine interest among users.
Of course it is also a matter of preferences and the eyes and displays



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