>From 5546a5f216f91c61161c6e05bf17b1ad7afca56a Mon Sep 17 00:00:00 2001
From: Byeongsik Jeon <address@hidden>
Date: Tue, 9 Oct 2018 07:33:10 +0900
Subject: [PATCH v2] Improve FT_Outline_Embolden for the unintended artifacts
 (#45596).
To: freetype-devel <address@hidden>

FreeType-Bugs: https://savannah.nongnu.org/bugs/?45596
---
 src/base/ftoutln.c | 121 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 121 insertions(+)

diff --git a/src/base/ftoutln.c b/src/base/ftoutln.c
index 85a469737..046b9c4d6 100644
--- a/src/base/ftoutln.c
+++ b/src/base/ftoutln.c
@@ -892,6 +892,7 @@
 
   /* documentation is in ftoutln.h */
 
+#if 0
   FT_EXPORT_DEF( FT_Error )
   FT_Outline_EmboldenXY( FT_Outline*  outline,
                          FT_Pos       xstrength,
@@ -1023,7 +1024,127 @@
 
     return FT_Err_Ok;
   }
+#else
+
+  FT_EXPORT_DEF( FT_Error )
+  FT_Outline_EmboldenXY( FT_Outline* outline,
+                         FT_Pos      xstrength,
+                         FT_Pos      ystrength )
+  {
+    FT_Vector*      points;
+    FT_Orientation  orientation;
+    FT_Vector       strength;
+    FT_Int          n_cont, n_first, n_last;
+
+    if ( !outline ) return FT_THROW( Invalid_Outline );
+
+    strength.x = xstrength / 2;
+    strength.y = ystrength / 2;
+    if ( strength.x == 0 && strength.y == 0 ) return FT_Err_Ok;
+
+    orientation = FT_Outline_Get_Orientation( outline );
+    if ( orientation == FT_ORIENTATION_NONE )
+    {
+      if ( outline->n_contours ) return FT_THROW( Invalid_Argument );
+      else return FT_Err_Ok;
+    }
+
+    points = outline->points;
+
+    for ( n_cont = n_first = 0; n_cont < outline->n_contours;
+          n_cont++, n_first = n_last + 1 )
+    {
+      FT_Vector in, out, anchor, shift;
+      FT_Fixed  det, deg, l_out, l_anchor;
+      FT_Int    n_tail, n_head, n_prev, n_anchor;
+      FT_Fixed  a, b, c, k;
+
+      n_last = outline->contours[n_cont];
+      n_anchor = -1;
+      in.x = in.y = anchor.x = anchor.y = 0;
+
+      for ( n_prev = n_last, n_head = n_first; n_head <= n_last;
+            n_prev = n_head, n_head++ )
+      {
+        out.x = points[n_head].x - points[n_prev].x;
+        out.y = points[n_head].y - points[n_prev].y;
+        l_out = FT_Vector_NormLen( &out );
+
+        if ( l_out == 0 ) continue;
+
+        det = FT_MulFix( in.x, out.y ) - FT_MulFix( in.y, out.x );
+        if ( det != 0 )
+        {
+          anchor = in = out;
+          l_anchor = l_out;
+          n_anchor = n_tail = n_head;
+          break;
+        }
+
+        in = out;
+      }
+
+      while ( n_anchor != -1 )
+      {
+        n_prev = n_head;
+        n_head = ( n_head < n_last )? n_head + 1 : n_first;
+        if ( n_head != n_anchor )
+        {
+          out.x = points[n_head].x - points[n_prev].x;
+          out.y = points[n_head].y - points[n_prev].y;
+          l_out = FT_Vector_NormLen( &out );
+        }
+        else
+        {
+          out = anchor;
+          l_out = l_anchor;
+          n_anchor = -1;
+        }
 
+        if ( l_out == 0 ) continue;
+
+        deg = FT_MulFix( in.x, out.x ) + FT_MulFix( in.y, out.y );
+        if ( deg == -0x10000L ) continue; /* overlapped segment */
+
+        /* deg = in.x * out.x + in.y * out.y = -cos(theta)
+         * f(deg) = a * deg^2 + b * deg + d
+         * f(1)  = 1       , theta = 180
+         * f(0)  = sqrt(2) , theta = 90, 270
+         * f(-1) = k       , theta = 0, 360
+         */
+        k = (FT_Fixed)( 1.5 * 65536. );
+        c = 92682L; /* sqrt(2) */
+        b = FT_MulDiv( 65536L, 65536L - k, 2 * 65536L );
+        a = FT_MulDiv( 65536L, k + 65536L, 2 * 65536L ) - 92682L;
+        deg = FT_MulFix( a, FT_MulFix( deg, deg )) + FT_MulFix( b, deg ) + c;
+        /* f(deg) = a * deg + b , not controllable */
+        /* deg = FT_MulFix( -27146L, deg ) + 92682L; */
+
+        shift.x = in.y + out.y;
+        shift.y = in.x + out.x;
+        if ( orientation == FT_ORIENTATION_TRUETYPE )
+          shift.x = -shift.x;
+        else
+          shift.y = -shift.y;
+        FT_Vector_NormLen( &shift );
+
+        shift.x = FT_MulFix( strength.x, FT_MulFix( shift.x, deg ) );
+        shift.y = FT_MulFix( strength.y, FT_MulFix( shift.y, deg ) );
+
+        for ( ; n_tail != n_head;
+                n_tail = ( n_tail < n_last )? n_tail + 1 : n_first )
+        {
+          points[n_tail].x += strength.x + shift.x;
+          points[n_tail].y += strength.y + shift.y;
+        }
+
+        in = out;
+      }
+    }
+
+    return FT_Err_Ok;
+  }
+#endif
 
   /* documentation is in ftoutln.h */
 
-- 
2.19.1