commit dd78d4a77458fa572c633b81e1f84b567f981ecc
author Alexei Podtelezhnikov <apodtele@gmail.com> Thu Mar 16 03:28:59 2023 +0000
committer Alexei Podtelezhnikov <apodtele@gmail.com> Thu Mar 16 03:28:59 2023 +0000
tree 464a907c640a2ea78766d834f943b65f7d04d1e8
parent 764bc8e41c19dac021e4ffe6ec6a207ed09df69a

* src/base/ftsynth.c (FT_GlyphSlot_AdjustWeight): New API.

include/freetype/ftsynth.h

diff --git a/include/freetype/ftsynth.h b/include/freetype/ftsynth.h
index 5d19697..af90967 100644
--- a/include/freetype/ftsynth.h
+++ b/include/freetype/ftsynth.h
@@ -68,6 +68,18 @@
   FT_EXPORT( void )
   FT_GlyphSlot_Embolden( FT_GlyphSlot  slot );
 
+  /* Precisely adjust the glyph weight either horizontally or vertically.  */
+  /* The `xdelta` and `ydelta` values are fractions of the face Em size    */
+  /* (in fixed-point format).  Considering that a regular face would have  */
+  /* stem widths on the order of 0.1 Em, a delta of 0.05 (0x0CCC) should   */
+  /* be very noticeable.  To increase or decrease the weight, use positive */
+  /* or negative values, respectively.                                     */
+  FT_EXPORT( void )
+  FT_GlyphSlot_AdjustWeight( FT_GlyphSlot  slot,
+                             FT_Fixed      xdelta,
+                             FT_Fixed      ydelta );
+
+
   /* Slant an outline glyph to the right by about 12 degrees.              */
   FT_EXPORT( void )
   FT_GlyphSlot_Oblique( FT_GlyphSlot  slot );

src/base/ftsynth.c

diff --git a/src/base/ftsynth.c b/src/base/ftsynth.c
index 6ec25e1..f32edd3 100644
--- a/src/base/ftsynth.c
+++ b/src/base/ftsynth.c
@@ -98,8 +98,17 @@
   FT_EXPORT_DEF( void )
   FT_GlyphSlot_Embolden( FT_GlyphSlot  slot )
   {
+    FT_GlyphSlot_AdjustWeight( slot, 0x0AAA, 0x0AAA );
+  }
+
+
+  FT_EXPORT_DEF( void )
+  FT_GlyphSlot_AdjustWeight( FT_GlyphSlot  slot,
+                             FT_Fixed      xdelta,
+                             FT_Fixed      ydelta )
+  {
     FT_Library  library;
-    FT_Face     face;
+    FT_Size     size;
     FT_Error    error;
     FT_Pos      xstr, ystr;
 
@@ -108,16 +117,15 @@
       return;
 
     library = slot->library;
-    face    = slot->face;
+    size    = slot->face->size;
 
     if ( slot->format != FT_GLYPH_FORMAT_OUTLINE &&
          slot->format != FT_GLYPH_FORMAT_BITMAP  )
       return;
 
-    /* some reasonable strength */
-    xstr = FT_MulFix( face->units_per_EM,
-                      face->size->metrics.y_scale ) / 24;
-    ystr = xstr;
+    /* express deltas in pixels in 26.6 format */
+    xstr = (FT_Pos)size->metrics.x_ppem * xdelta / 1024;
+    ystr = (FT_Pos)size->metrics.y_ppem * ydelta / 1024;
 
     if ( slot->format == FT_GLYPH_FORMAT_OUTLINE )
       FT_Outline_EmboldenXY( &slot->outline, xstr, ystr );