ref: 0d5f1dd37c056b4460a460d16fd1fbb06740e891
parent: 7bdf386e758cb7c01392e625f4d723e5abb3f9a6
author: Tatsuyuki Ishi <ishitatsuyuki@gmail.com>
date: Fri Dec 18 17:10:30 EST 2020
[autofit] Fix double division in stem darkening. The old code used to divide the darkening amount by em_ratio twice, leading to unnecessarily bold stems on certain fonts with higher units per em (e.g. Inter). This patch fixes it. The return value of af_loader_compute_darkening was also changed to use 16.16 fixed point to get rid of a redundant truncation operation. This should slightly improve the precision, although it's still bottlenecked by the emboldening function, which uses 26.6 fixed point. * src/autofit/afloader.[ch] (af_loader_compute_darkening): Return FT_Fixed. (af_loader_embolden_glyph_in_slot): Revise calculations.
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,20 @@
+2020-12-18 Tatsuyuki Ishi <ishitatsuyuki@gmail.com>
+
+ [autofit] Fix double division in stem darkening.
+
+ The old code used to divide the darkening amount by em_ratio twice,
+ leading to unnecessarily bold stems on certain fonts with higher
+ units per em (e.g. Inter). This patch fixes it.
+
+ The return value of af_loader_compute_darkening was also changed to
+ use 16.16 fixed point to get rid of a redundant truncation operation.
+ This should slightly improve the precision, although it's still
+ bottlenecked by the emboldening function, which uses 26.6 fixed point.
+
+ * src/autofit/afloader.[ch]
+ (af_loader_compute_darkening): Return FT_Fixed.
+ (af_loader_embolden_glyph_in_slot): Revise calculations.
+
2020-12-17 Alexei Podtelezhnikov <apodtele@gmail.com>
* include/freetype/ftmodapi.h (FT_FACE_DRIVER_NAME): New public macro.
--- a/src/autofit/afloader.c
+++ b/src/autofit/afloader.c
@@ -105,7 +105,6 @@
globals->stem_darkening_for_ppem;
FT_Fixed em_size = af_intToFixed( face->units_per_EM );
- FT_Fixed em_ratio = FT_DivFix( af_intToFixed( 1000 ), em_size );
FT_Matrix scale_down_matrix = { 0x10000L, 0, 0, 0x10000L };@@ -142,12 +141,11 @@
darken_by_font_units_x =
- af_intToFixed( af_loader_compute_darkening( loader,
- face,
- stdVW ) );
- darken_x = FT_DivFix( FT_MulFix( darken_by_font_units_x,
- size_metrics->x_scale ),
- em_ratio );
+ af_loader_compute_darkening( loader,
+ face,
+ stdVW ) ;
+ darken_x = FT_MulFix( darken_by_font_units_x,
+ size_metrics->x_scale );
globals->standard_vertical_width = stdVW;
globals->stem_darkening_for_ppem = size_metrics->x_ppem;
@@ -161,12 +159,11 @@
darken_by_font_units_y =
- af_intToFixed( af_loader_compute_darkening( loader,
- face,
- stdHW ) );
- darken_y = FT_DivFix( FT_MulFix( darken_by_font_units_y,
- size_metrics->y_scale ),
- em_ratio );
+ af_loader_compute_darkening( loader,
+ face,
+ stdHW ) ;
+ darken_y = FT_MulFix( darken_by_font_units_y,
+ size_metrics->y_scale );
globals->standard_horizontal_width = stdHW;
globals->stem_darkening_for_ppem = size_metrics->x_ppem;
@@ -594,7 +591,7 @@
*
* XXX: Currently a crude adaption of the original algorithm. Do better?
*/
- FT_LOCAL_DEF( FT_Int32 )
+ FT_LOCAL_DEF( FT_Fixed )
af_loader_compute_darkening( AF_Loader loader,
FT_Face face,
FT_Pos standard_width )
@@ -713,7 +710,7 @@
}
/* Convert darken_amount from per 1000 em to true character space. */
- return af_fixedToInt( FT_DivFix( darken_amount, em_ratio ) );
+ return FT_DivFix( darken_amount, em_ratio );
}
--- a/src/autofit/afloader.h
+++ b/src/autofit/afloader.h
@@ -75,7 +75,7 @@
FT_UInt gindex,
FT_Int32 load_flags );
- FT_LOCAL_DEF( FT_Int32 )
+ FT_LOCAL_DEF( FT_Fixed )
af_loader_compute_darkening( AF_Loader loader,
FT_Face face,
FT_Pos standard_width );