bugThe FreeType Project - Bugs: bug #41421, Possible bug? Incorrect rendering...

 
 

bug #41421: Possible bug? Incorrect rendering of bold capital DELTA in some fonts

Submitted by:  Sergio Callegari <callegar>
Submitted on:  Sat 01 Feb 2014 03:38:03 PM UTC  
 
Severity: 3 - NormalItem Group: Incorrect behaviour
Status: DuplicatePrivacy: Public
Assigned to: Werner LEMBERG <wl>Open/Closed: Closed
Planned Release: 2.5.3

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Tue 04 Feb 2014 02:20:26 PM UTC, comment #7:

Bug fixed in latest Dejavu fonts snapshot.

- can definitely be closed here

- thanks for having been extremely helpful in finding the actual issue and in managing getting it fixed so fast.

Sergio Callegari <callegar>
Mon 03 Feb 2014 11:23:51 AM UTC, comment #6:

It's up to the font whether hinting still applies at large DPI values. Normally, hinting is always enabled – some fonts (mainly for CJK scripts) even need hinting at any size since bytecode instructions are used to position and scale subglyphs.

And yes, it's a bug in DejaVu; theoretically, there should already be a bug report, so please check that and increase its `importance level' :-)

Regarding the configuration, I fear you are out of luck in general. While it is possible to configure `fontconfig' so that this font get hinted with FreeType's auto-hinter, this is not a general solution working everywhere. In particular, ghostscript doesn't use it. However, you can configure ghostscript to replace this font with something else, AFAIK, but I don't know the details.

On the other hand, the font substitution chain should be fully controllable with `fontconfig'. Again, this needs cooperation with the application, this is, the application must use fontconfig for accessing fonts.

Werner LEMBERG <wl>
Project AdministratorIn charge of this item.
Mon 03 Feb 2014 11:03:59 AM UTC, comment #5:

Thanks for clarifying (and also for clearing my wrong hypothesis about which app uses freetype and which one does not).

Out of curiosity... I understand that the issue comes from the hinting info in the font. Why do I see it when the file is printed on a postscript printer? Hasn't hinting to do with translation to lowres rasters? Does the printer use hinting itself for its 1200dpi output? Or is the hinting involved in the transformation of the PDF file into the ps one passed to the printer?

Finally and most important...

1) Is this ultimately a bug in the dejavu font? Should I report it there?

2) Is there any 'configuration based' workaround that I can use? E.g. Instruct system (and printer?) not to use the hinting in dejavu sans bold? Instruct system to never use dejavu sans bold as a substitute for sans fonts that do not have greek?

Thanks in advance for any help...

Sergio Callegari <callegar>
Sun 02 Feb 2014 04:23:33 PM UTC, comment #4:

Regarding Foxit: They actually use FreeType as the rendering engine :-)

Werner LEMBERG <wl>
Project AdministratorIn charge of this item.
Sun 02 Feb 2014 04:21:15 PM UTC, comment #3:

OK, now everything's clear. This is a duplicate of issue #40975.

And just to rectify: Acrobat on GNU/Linux boxes does not use FreeType for rendering TrueType fonts! They are using an adapted version of Microsoft's TT engine.

BTW, if the problematic glyph gets hinted with FreeType's auto-hinter, the rendering is correct.

Werner LEMBERG <wl>
Project AdministratorIn charge of this item.
Sun 02 Feb 2014 03:53:28 PM UTC, comment #2:

Sorry for being to vague.

Made some further tests.

1) Libreoffice/openoffice, etc. have nothing to do with it.
Problem is evident even starting from regular PDF.

2) Source Sans Pro and Istok fonts have nothing to do with it.
I was experiencing issues with them because /they do not include greek chars/ a case where the system includes the default sans font, in this case DejaVuSans-Bold.

Now I have a minimal pdf file showing the issue (attached).

When ghostscript deals with this file (convert to ps for printing on a ps printer, convert to a bitmap to print on a non ps printer), it misrenders the delta char (see example).

When acroread on linux (also freetype based) deals with this file it misrenders the delta char (even on screen).

When the pdf file is dealt with using windows based apps (foxit pdf reader under wine, to say one) there are no issues at all.

(file #30437)

Sergio Callegari <callegar>
Sat 01 Feb 2014 06:02:33 PM UTC, comment #1:

Unfortunately, this is far too vague. I suggest that you create a minimum test document (embedding the problematic font, in case this is possible for a libreoffice document) that reliably reproduces the issue. Then file a libreoffice bug report. In case FreeType is the problem the libreoffice people will certainly contact us.

For this reason, I close this report as invalid. Sorry.

Werner LEMBERG <wl>
Project AdministratorIn charge of this item.
Sat 01 Feb 2014 03:38:03 PM UTC, original submission:

Experiencing the following

On kubuntu Linux 13.10
Either with stock Freetype 2.4 or with 2.5.2

I have a libreoffice (4.2.0) document including some greek letters.

If this is formatted using certain fonts (e.g. istok, source sans pro), there are issues with the bold greek capital letter delta. Other fonts do not seem to show the issue.

- it may display good or bad on screen libreoffice (depending on the selected font size). When it displays bad, the shape of the delta is filled in black

- it typically displays fine in pdf viewers if the document is exported to PDF.

- it always prints bad on postscript printers. This happens either when printing from libreoffice and when printing from a pdf viewer in linux from the pdf exported by libreoffice. In this case, the delta symbol is filled.

- it converts to bad postscript when running pdftops (ghostscript) on the exported pdf (delta symbol is filled).

Any clue?

Sergio Callegari <callegar>

 

(Note: upload size limit is set to 16384 kB, after insertion of the required escape characters.)

Attach File(s):
   
   
Comment:
   

Attached Files
file #30438:  test.png added by callegar (595B - image/png)
file #30437:  test.pdf added by callegar (8KiB - application/pdf - Test files)

 

Depends on the following items: None found

Items that depend on this one: None found

 

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  • -unavailable- added by wl (Posted a comment)
  • -unavailable- added by callegar (Submitted the item)
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    Follow 7 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Sun 02 Feb 2014 04:21:15 PM UTCwlStatusInvalid=>Duplicate
      Planned ReleaseNone=>2.5.3
    Sun 02 Feb 2014 04:04:03 PM UTCcallegarAttached File-=>Added test.png, #30438
    Sun 02 Feb 2014 03:53:28 PM UTCcallegarAttached File-=>Added test.pdf, #30437
    Sat 01 Feb 2014 06:02:33 PM UTCwlStatusNone=>Invalid
      Assigned toNone=>wl
      Open/ClosedOpen=>Closed

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