Re: [Devel] Postscript hinter and non-square pixels

[David Turner]

Hi Again,

  OK, I think I've posted a fix. My tests are now running OK,
  could you tell me if this solves your problem..

Regards,

- David




David Turner a écrit :
> 
> Hi Detlef,
> 
>   There is nothing in the Postscript hinter that assumes square
>   pixel. It's most probably a bug where coordinates and hints have
>   their scale factors inversed by accident..
> 
>   I've just quickyl hacked "ftstring", which doesn't use the cache,
>   to check that, I'll let you know later..
> 
> Regards,
> 
> - David
> 
> Detlef Würkner a écrit :
> >
> > Hello!
> >
> > I wrote:
> >
> > > While playing around with display resolution aspect ratio adaptive code,
> > > I found that the Postscript hinter produces really big errors when
> > > setting the horizontal resolution to the double value of the vertical
> > > resolution with FT_Set_Char_Size() to be displayed correct on an Amiga
> > > NTSC screen.
> > >
> > > The horizontal line of an "A" is e.g. not displayed...
> > > With autohinter and without hinter the problem does not appear.
> >
> > After the various fixes and enhancements to the PostScript hinter it
> > looks better, but the main problem seems to stay: The PostScript hinter
> > assumes square pixels. Is this an inherent problem of PostScript hints,
> > of the used font or of the hinter?
> >
> > To reproduce: I tested with the GhostScript fonts and with Adobe Sans MM
> > (from Acrobat Reader IMHO). When specifying non-square pixels with e.g.
> > FT_Set_Char_Size(face, 16*64, 0, 72, 36), we tell FreeType that the pixels
> > are non-square, 72 dpi horizontal and 36 dpi vertical, e.g. a TV screen
> > in non-interlace mode. If displayed on a computer monitor with square
> > pixels, an "o" should be about twice as wide than high, on a TV in highres
> > non-interlace mode, it should be nearly round.
> >
> > When specifying FT_LOAD_NO_HINTING or FT_LOAD_FORCE_AUTOHINT this works
> > as expected, but without specifying one of these flags the PostScript
> > hinter is used and it always produces a nearly round "o". The TrueType
> > hinter works fine. Whether generating monochrome or gray bitmaps makes no
> > difference. Oh, and I didn't test without glyphcache, so not
> > FT_Set_Char_Size() was used but pix_width and pix_height of
> > FTC_Image_Desc had different values.
> >
> > Ciao, Detlef
> > --
> > _ // address@hidden
> > \X/  Detlef Wuerkner, Langgoens/Germany
> >
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> 
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