Bug 23539

Summary:	bitmap font is not scaled by cairo_scale()
Product:	cairo	Reporter:	Ginn Chen <ginn.chen>
Component:	freetype font backend	Assignee:	David Turner <david>
Status:	RESOLVED FIXED	QA Contact:	cairo-bugs mailing list <cairo-bugs>
Severity:	normal
Priority:	medium	CC:	ajohnson, freedesktop
Version:	1.9.3
Hardware:	All
OS:	Linux (All)
Whiteboard:
i915 platform:		i915 features:
Attachments:	cairo_bitmap_font_scale.c try.patch the buggy result result after applying try.patch

Description Ginn Chen 2009-08-27 02:23:31 UTC

Created attachment 28944 [details]
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".

Comment 1 Ginn Chen 2009-08-27 02:25:34 UTC

Created attachment 28945 [details] [review]
try.patch

Comment 2 Ginn Chen 2009-08-27 02:26:06 UTC

Created attachment 28946 [details]
the buggy result

Comment 3 Ginn Chen 2009-08-27 02:27:50 UTC

Created attachment 28947 [details]
result after applying try.patch

Comment 4 Adrian Johnson 2009-08-27 05:11:55 UTC

> 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".

User fonts is the feature that will give you better control of bitmap fonts in PS/PDF output:

  http://www.cairographics.org/manual/cairo-user-font.html

An example of creating bitmap fonts using user fonts is in cairo/test/user-font-mask.c

Comment 5 Behdad Esfahbod 2009-08-27 11:04:32 UTC

This issue (how to scale bitmaps) should be brought up on cairo list for discussion first.  Thanks.

Comment 6 Behdad Esfahbod 2012-12-30 00:53:21 UTC

This is now being discussed:
http://lists.freedesktop.org/archives/fontconfig/2012-December/004498.html

Comment 7 Behdad Esfahbod 2012-12-31 01:22:46 UTC

In fact, this recent commit of mind fixed your test case:

http://cgit.freedesktop.org/cairo/commit/?id=b94a519aad3d5b50aa6de47ee16ee6a099de9791

The fontconfig part is still ongoing, but that's not in the scope of this bug anymore.  That said, there seems to be issues with vertical text and bitmap fonts, so someone may want to investigate.

Comment 8 Behdad Esfahbod 2015-05-01 19:38:50 UTC

This should be fixed now.

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