[cairo-bugs] [Bug 23539] New: bitmap font is not scaled by cairo_scale()

[bugzilla-daemon at freedesktop.org]

http://bugs.freedesktop.org/show_bug.cgi?id=23539

           Summary: bitmap font is not scaled by cairo_scale()
           Product: cairo
           Version: 1.9.3
          Platform: All
        OS/Version: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: freetype font backend
        AssignedTo: david at freetype.org
        ReportedBy: ginn.chen at sun.com
         QAContact: cairo-bugs at cairographics.org
                CC: ajohnson at redneon.com


Created an attachment (id=28944)
 --> (http://bugs.freedesktop.org/attachment.cgi?id=28944)
cairo_bitmap_font_scale.c

This bug was reported as bug 18001 about 1 year ago.
Actually it is not only reproducible with PS backend, but also with image and
PDF backend perhaps all backend.
It is not only reproducible with freetype fonts either. I can reproduce it with
Windows. See (https://bugzilla.mozilla.org/show_bug.cgi?id=448186)

However I filed this bug against freetype font backend, because I think
different font backend may require different fixes.
Please correct me if I were wrong.

Steps to reproduce:
1) Enable bitmap font on Ubuntu or use Solaris.
See: http://www.alanbriolat.co.uk/2009/04/enable-bitmap-fonts-on-ubuntu-jaunty/

2) Run fc-match Courier
Make sure you get a *.pcf or *.pcf.gz file.

3) Compile and run attached cairo_bitmap_font_scale.c.

4) If you change "Courier" to a non bitmap font, the result is correct.

I've proposed a draft fix half a year ago in mozilla bug 448186.
Attached try.patch.

However I don't think it's the right fix.
If we do _transform_glyph_bitmap() there, it will make the glyph unreadable if
it is scaled down to 50% or 30%.

For PS, if we use "scale" operator inside "/Glyphs", we can get a better
result.
(suggested by Adrian Johnson in
https://bugzilla.mozilla.org/show_bug.cgi?id=448186#c7)
But I don't know how should I pass the "CTM" through "scaled_glyph".


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