From: Eric Rannaud <e@xxxxxxxxxxxxxxxx>
When lcdfilter is set to "lcdcustom", use lcdfiltercustom to retrieve a
string containing a space-separated list of double values between 0.0
and 1.0 and configure the renderer LCD filter (e.g. for freetype2, this
is done with FT_Library_SetLcdFilterWeights()).
If lcdfiltercustom is empty or is malformed, fontconfig users should
fallback to lcddefault.
With freetype2 as renderer, when fontconfig's FC_LCD_DEFAULT is mapped
to freetype2's FT_LCD_FILTER_DEFAULT, the configuration
<match target="font">
<edit mode="assign" name="lcdfilter">
<const>lcddefault</const>
</edit>
</match>
corresponds to setting
<match target="font">
<edit mode="assign" name="lcdfilter">
<const>lcdcustom</const>
</edit>
</match>
<match target="font">
<edit mode="assign" name="lcdfiltercustom">
<string>.0625 .25 .4375 .25 .0625</string>
</edit>
</match>
---
Hi,
Freetype2 has FT_Library_SetLcdFilterWeights() to control the configuration of
the filter used for LCD antialiasing. This gives more control than
FT_LCD_FILTER_DEFAULT, _LIGHT, _LEGACY, ... For instance, with:
static const FT_Byte heavy_filter[5] = { 0x40, 0x80, 0x90, 0x80, 0x40 };
fonts are rendered bolder (see http://goo.gl/YHpNs, on the right is lcddefault).
Some users with poor eyesight will want to tweak this setting to make fonts more
readable, especially on low-res screens (e.g. a 24" 1920x1200 screen).
Fontconfig has an option to control the LCD AA filter, but only via a few
predefined values: lcdfilter can be set to lcdnone, lcddefault, lcdlight, or
lcdlegacy. However, other configurations for this filter are reasonable (e.g.
the one above, or those listed in http://www.infinality.net/files/infinality-settings).
This patch adds a fontconfig option to control the LCD filter directly.
For reference, see the freetype-devel discussion at
http://lists.nongnu.org/archive/html/freetype-devel/2011-11/msg00023.html
A few questions:
- Is a string the best way to set a list of values with fontconfig?
- Should we prefer values between 0 and 1000 instead of Double between 0 and 1?
Note that in freetype2, the filter is actually using 5 uint8_t values between
0 and 255 so rounding errors will affect the actual values used.
- Would you prefer a unique "lcdheavy" value for lcdfilter, corresponding to a new
FT_LCD_FILTER_HEAVY in freetype2 for some fixed, and somewhat arbitrary,
LCD filter configuration? The freetype2 developers are open to the idea, but I
think we would all prefer complete control over the filter values.
I will have patches for Cairo and Xft to have them honor the new config option,
parse the list of filter values, and call FT_Library_SetLcdFilterWeights(). Any
other major users of fontconfig I should write patches for and submit upstream?
Thanks,
Eric.
---
doc/fontconfig-user.sgml | 5 +++++
fontconfig/fontconfig.h | 2 ++
src/fcname.c | 4 +++-
3 files changed, 10 insertions(+), 1 deletions(-)
diff --git a/doc/fontconfig-user.sgml b/doc/fontconfig-user.sgml
index 217feb9..d0944ba 100644
--- a/doc/fontconfig-user.sgml
+++ b/doc/fontconfig-user.sgml
@@ -122,6 +122,10 @@ convenience for the applications' rendering mechanism.
rgba Int unknown, rgb, bgr, vrgb, vbgr,
none - subpixel geometry
lcdfilter Int Type of LCD filter
+ lcdfiltercustom String Weights for the custom LCD filter, enabled by setting
+ lcdfilter to lcdcustom. Example: with freetype2 as
+ renderer, ".0625 .25 .4375 .25 .0625" corresponds to
+ setting the option lcdfilter to lcddefault.
minspace Bool Eliminate leading from line spacing
charset CharSet Unicode chars encoded by the font
lang String List of RFC-3066-style languages this
@@ -494,6 +498,7 @@ symbolic names for common font values:
lcddefault lcdfilter 1
lcdlight lcdfilter 2
lcdlegacy lcdfilter 3
+ lcdcustom lcdfilter 4
hintnone hintstyle 0
hintslight hintstyle 1
hintmedium hintstyle 2
diff --git a/fontconfig/fontconfig.h b/fontconfig/fontconfig.h
index db26b97..f05f570 100644
--- a/fontconfig/fontconfig.h
+++ b/fontconfig/fontconfig.h
@@ -111,6 +111,7 @@ typedef int FcBool;
#define FC_EMBEDDED_BITMAP "embeddedbitmap" /* Bool - true to enable embedded bitmaps */
#define FC_DECORATIVE "decorative" /* Bool - true if style is a decorative variant */
#define FC_LCD_FILTER "lcdfilter" /* Int */
+#define FC_LCD_FILTER_CUSTOM "lcdfiltercustom" /* String. Space separated list of double */
#define FC_CACHE_SUFFIX ".cache-"FC_CACHE_VERSION
#define FC_DIR_CACHE_FILE "fonts.cache-"FC_CACHE_VERSION
@@ -177,6 +178,7 @@ typedef int FcBool;
#define FC_LCD_DEFAULT 1
#define FC_LCD_LIGHT 2
#define FC_LCD_LEGACY 3
+#define FC_LCD_CUSTOM 4
typedef enum _FcType {
FcTypeVoid,
diff --git a/src/fcname.c b/src/fcname.c
index d77eff6..0697d10 100644
--- a/src/fcname.c
+++ b/src/fcname.c
@@ -75,7 +75,8 @@ static const FcObjectType _FcBaseObjectTypes[] = {
{ FC_EMBOLDEN, FcTypeBool },
{ FC_EMBEDDED_BITMAP, FcTypeBool },
{ FC_DECORATIVE, FcTypeBool },
- { FC_LCD_FILTER, FcTypeInteger }, /* 41 */
+ { FC_LCD_FILTER, FcTypeInteger },
+ { FC_LCD_FILTER_CUSTOM, FcTypeString }, /* 42 */
};
#define NUM_OBJECT_TYPES (sizeof _FcBaseObjectTypes / sizeof _FcBaseObjectTypes[0])
@@ -454,6 +455,7 @@ static const FcConstant _FcBaseConstants[] = {
{ (FcChar8 *) "lcddefault", "lcdfilter", FC_LCD_DEFAULT },
{ (FcChar8 *) "lcdlight", "lcdfilter", FC_LCD_LIGHT },
{ (FcChar8 *) "lcdlegacy", "lcdfilter", FC_LCD_LEGACY },
+ { (FcChar8 *) "lcdcustom", "lcdfilter", FC_LCD_CUSTOM },
};
#define NUM_FC_CONSTANTS (sizeof _FcBaseConstants/sizeof _FcBaseConstants[0])
--
1.7.6.4
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