Commit 495bd3cc4f54f5f4604709391a716fcd0c033277
2012-06-06T13:24:04
[ftraster] Fix rounding issue causing visual artifacts. Problem reported by jola <hans-jochen.lau@lhsystems.com>; see http://lists.gnu.org/archive/html/freetype-devel/2012-05/msg00036.html * src/raster/ftraster.c (SMulDiv_No_Round): New macro. (Line_Up): Use it. * src/raster/ftmisc.h (FT_MulDiv_No_Round): Copied from `ftcalc.c'.
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diff --git a/ChangeLog b/ChangeLog
index d2f6465..cbf9679 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2012-06-06 Werner Lemberg <wl@gnu.org>
+
+ [ftraster] Fix rounding issue causing visual artifacts.
+
+ Problem reported by jola <hans-jochen.lau@lhsystems.com>; see
+
+ http://lists.gnu.org/archive/html/freetype-devel/2012-05/msg00036.html
+
+ * src/raster/ftraster.c (SMulDiv_No_Round): New macro.
+ (Line_Up): Use it.
+ * src/raster/ftmisc.h (FT_MulDiv_No_Round): Copied from `ftcalc.c'.
+
2012-05-28 Alexei Podtelezhnikov <apodtele@gmail.com>
* src/base/ftoutln.c (FT_Outline_Get_Orientation): Simplify.
diff --git a/src/raster/ftmisc.h b/src/raster/ftmisc.h
index 7773924..703155a 100644
--- a/src/raster/ftmisc.h
+++ b/src/raster/ftmisc.h
@@ -115,6 +115,27 @@
return ( s > 0 ) ? d : -d;
}
+
+ static FT_Long
+ FT_MulDiv_No_Round( FT_Long a,
+ FT_Long b,
+ FT_Long c )
+ {
+ FT_Int s;
+ FT_Long d;
+
+
+ s = 1;
+ if ( a < 0 ) { a = -a; s = -1; }
+ if ( b < 0 ) { b = -b; s = -s; }
+ if ( c < 0 ) { c = -c; s = -s; }
+
+ d = (FT_Long)( c > 0 ? (FT_Int64)a * b / c
+ : 0x7FFFFFFFL );
+
+ return ( s > 0 ) ? d : -d;
+ }
+
#endif /* __FTMISC_H__ */
diff --git a/src/raster/ftraster.c b/src/raster/ftraster.c
index f85845e..7d5bcae 100644
--- a/src/raster/ftraster.c
+++ b/src/raster/ftraster.c
@@ -60,7 +60,7 @@
#include <ft2build.h>
#include "ftraster.h"
-#include FT_INTERNAL_CALC_H /* for FT_MulDiv only */
+#include FT_INTERNAL_CALC_H /* for FT_MulDiv and FT_MulDiv_No_Round */
#include "rastpic.h"
@@ -255,7 +255,8 @@
/* On the other hand, SMulDiv means `Slow MulDiv', and is used typically */
/* for clipping computations. It simply uses the FT_MulDiv() function */
/* defined in `ftcalc.h'. */
-#define SMulDiv FT_MulDiv
+#define SMulDiv FT_MulDiv
+#define SMulDiv_No_Round FT_MulDiv_No_Round
/* The rasterizer is a very general purpose component; please leave */
/* the following redefinitions there (you never know your target */
@@ -1150,14 +1151,14 @@
if ( Dx > 0 )
{
- Ix = SMulDiv( ras.precision, Dx, Dy);
+ Ix = SMulDiv_No_Round( ras.precision, Dx, Dy );
Rx = ( ras.precision * Dx ) % Dy;
Dx = 1;
}
else
{
- Ix = SMulDiv( ras.precision, -Dx, Dy) * -1;
- Rx = ( ras.precision * -Dx ) % Dy;
+ Ix = -SMulDiv_No_Round( ras.precision, -Dx, Dy );
+ Rx = ( ras.precision * -Dx ) % Dy;
Dx = -1;
}