ref: aba0f498c3f01631262a4bca1f7f933c2833226f
parent: d0422b23d3f64631f0aee9a3378ee3e33b75cc92
author: Alexei Podtelezhnikov <[email protected]>
date: Fri Oct 24 19:50:57 EDT 2014
Improve flat corner definition. * include/internal/ftcalc.h (FT_HYPOT): Macro to approximate Euclidean distance with the alpha max plus beta min algorithm. * src/base/ftcalc.c (ft_corner_is_flat): Use it instead of Taxicab metric.
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2014-10-25 Alexei Podtelezhnikov <[email protected]>
+
+ Improve flat corner definition.
+
+ * include/internal/ftcalc.h (FT_HYPOT): Macro to approximate Euclidean
+ distance with the alpha max plus beta min algorithm.
+ * src/base/ftcalc.c (ft_corner_is_flat): Use it instead of Taxicab
+ metric.
+
2014-10-23 David Weiß <[email protected]>
[build] Improve property file for vc2010.
--- a/include/internal/ftcalc.h
+++ b/include/internal/ftcalc.h
@@ -311,10 +311,11 @@
FT_Pos out_x,
FT_Pos out_y );
+
/*
* Return TRUE if a corner is flat or nearly flat. This is equivalent to
- * saying that the angle difference between the `in' and `out' vectors is
- * very small.
+ * saying that the corner point is close to its neighbors, or inside an
+ * ellipse defined by the neighbor focal points to be more precise.
*/
FT_BASE( FT_Int )
ft_corner_is_flat( FT_Pos in_x,
@@ -359,6 +360,15 @@
FT_BASE( FT_Fixed )
FT_Hypot( FT_Fixed x,
FT_Fixed y );
+
+
+ /*
+ * Approximate sqrt(x*x+y*y) using alpha max plus beta min algorithm.
+ */
+#define FT_HYPOT( x, y ) \
+ ( x = FT_ABS( x ), y = FT_ABS( y ), \
+ x > y ? x + ( 3 * y >> 3 ) \
+ : y + ( 3 * x >> 3 ) )
#if 0
--- a/src/base/ftcalc.c
+++ b/src/base/ftcalc.c
@@ -858,6 +858,8 @@
FT_Pos out_x,
FT_Pos out_y )
{+#if 0
+
FT_Pos ax = in_x;
FT_Pos ay = in_y;
@@ -901,6 +903,27 @@
if ( ay < 0 )
ay = -ay;
d_corner = ax + ay; /* d_corner = || in + out || */
+
+#else
+
+ FT_Pos ax = in_x + out_x;
+ FT_Pos ay = in_y + out_y;
+
+ FT_Pos d_in, d_out, d_corner;
+
+ /* The original implementation always returned TRUE */
+ /* for vectors from the same quadrant dues to additivity */
+ /* of Taxicab metric there. The alpha max plus beta min */
+ /* algorithm used here is additive within each octant, */
+ /* so we now reject some near 90-degree corners within */
+ /* quadrants, consistently with eliptic definition of */
+ /* flat corner. */
+
+ d_in = FT_HYPOT( in_x, in_y );
+ d_out = FT_HYPOT( out_x, out_y );
+ d_corner = FT_HYPOT( ax, ay );
+
+#endif
/* now do a simple length comparison: */
/* */