[autofit] Implement darkening computation function. This is a crude adaption of the original `cf2_computeDarkening' function. * src/autofit/afloader.c (af_intToFixed, af_fixedToInt, af_floatToFixed): New macros, taken from `cf2fixed.h'. (af_loader_compute_darkening): New function. * src/autofit/afloader.h: Updated.
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diff --git a/ChangeLog b/ChangeLog
index c380fb5..e9aaefe 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,17 @@
2015-11-02 Nikolaus Waxweiler <madigens@gmail.com>
+ [autofit] Implement darkening computation function.
+
+ This is a crude adaption of the original `cf2_computeDarkening'
+ function.
+
+ * src/autofit/afloader.c (af_intToFixed, af_fixedToInt,
+ af_floatToFixed): New macros, taken from `cf2fixed.h'.
+ (af_loader_compute_darkening): New function.
+ * src/autofit/afloader.h: Updated.
+
+2015-11-02 Nikolaus Waxweiler <madigens@gmail.com>
+
[autofit] Add functions to get standard widths for writing systems.
We need the computed standard horizontal and vertical widths for the
diff --git a/src/autofit/afloader.c b/src/autofit/afloader.c
index 722ffd3..615743e 100644
--- a/src/autofit/afloader.c
+++ b/src/autofit/afloader.c
@@ -405,4 +405,141 @@
}
+ /*
+ * Compute amount of font units the face should be emboldened by, in
+ * analogy to the CFF driver's `cf2_computeDarkening' function. See there
+ * for details of the algorithm.
+ *
+ * XXX: Currently a crude adaption of the original algorithm. Do better?
+ */
+#define af_intToFixed( i ) \
+ ( (FT_Fixed)( (FT_UInt32)(i) << 16 ) )
+#define af_fixedToInt( x ) \
+ ( (FT_Short)( ( (FT_UInt32)(x) + 0x8000U ) >> 16 ) )
+#define af_floatToFixed( f ) \
+ ( (FT_Fixed)( (f) * 65536.0 + 0.5 ) )
+
+ FT_LOCAL_DEF( FT_Int32 )
+ af_loader_compute_darkening( AF_Loader loader,
+ FT_Face face,
+ FT_Pos standard_width )
+ {
+ AF_Module module = loader->globals->module;
+
+ FT_UShort units_per_EM;
+ FT_Fixed ppem, em_ratio;
+ FT_Fixed stem_width, stem_width_per_1000, scaled_stem, darken_amount;
+ FT_Int log_base_2;
+ FT_Int x1, y1, x2, y2, x3, y3, x4, y4;
+
+
+ ppem = FT_MAX( af_intToFixed( 4 ),
+ af_intToFixed( face->size->metrics.x_ppem ) );
+ units_per_EM = face->units_per_EM;
+
+ em_ratio = FT_DivFix( af_intToFixed( 1000 ),
+ af_intToFixed ( units_per_EM ) );
+ if ( em_ratio < af_floatToFixed( .01 ) )
+ {
+ /* If something goes wrong, don't embolden. */
+ return 0;
+ }
+
+ x1 = module->darken_params[0];
+ y1 = module->darken_params[1];
+ x2 = module->darken_params[2];
+ y2 = module->darken_params[3];
+ x3 = module->darken_params[4];
+ y3 = module->darken_params[5];
+ x4 = module->darken_params[6];
+ y4 = module->darken_params[7];
+
+ if ( standard_width <= 0 )
+ {
+ stem_width = af_intToFixed( 75 ); /* taken from cf2font.c */
+ stem_width_per_1000 = stem_width;
+ }
+ else
+ {
+ stem_width = af_intToFixed( standard_width );
+ stem_width_per_1000 = FT_MulFix( stem_width, em_ratio );
+ }
+
+ log_base_2 = FT_MSB( (FT_UInt32)stem_width_per_1000 ) +
+ FT_MSB( (FT_UInt32)ppem );
+
+ if ( log_base_2 >= 46 )
+ {
+ /* possible overflow */
+ scaled_stem = af_intToFixed( x4 );
+ }
+ else
+ scaled_stem = FT_MulFix( stem_width_per_1000, ppem );
+
+ /* now apply the darkening parameters */
+ if ( scaled_stem < af_intToFixed( x1 ) )
+ darken_amount = FT_DivFix( af_intToFixed( y1 ), ppem );
+
+ else if ( scaled_stem < af_intToFixed( x2 ) )
+ {
+ FT_Int xdelta = x2 - x1;
+ FT_Int ydelta = y2 - y1;
+ FT_Int x = stem_width_per_1000 -
+ FT_DivFix( af_intToFixed( x1 ), ppem );
+
+
+ if ( !xdelta )
+ goto Try_x3;
+
+ darken_amount = FT_MulDiv( x, ydelta, xdelta ) +
+ FT_DivFix( af_intToFixed( y1 ), ppem );
+ }
+
+ else if ( scaled_stem < af_intToFixed( x3 ) )
+ {
+ Try_x3:
+ {
+ FT_Int xdelta = x3 - x2;
+ FT_Int ydelta = y3 - y2;
+ FT_Int x = stem_width_per_1000 -
+ FT_DivFix( af_intToFixed( x2 ), ppem );
+
+
+ if ( !xdelta )
+ goto Try_x4;
+
+ darken_amount = FT_MulDiv( x, ydelta, xdelta ) +
+ FT_DivFix( af_intToFixed( y2 ), ppem );
+ }
+ }
+
+ else if ( scaled_stem < af_intToFixed( x4 ) )
+ {
+ Try_x4:
+ {
+ FT_Int xdelta = x4 - x3;
+ FT_Int ydelta = y4 - y3;
+ FT_Int x = stem_width_per_1000 -
+ FT_DivFix( af_intToFixed( x3 ), ppem );
+
+
+ if ( !xdelta )
+ goto Use_y4;
+
+ darken_amount = FT_MulDiv( x, ydelta, xdelta ) +
+ FT_DivFix( af_intToFixed( y3 ), ppem );
+ }
+ }
+
+ else
+ {
+ Use_y4:
+ darken_amount = FT_DivFix( af_intToFixed( y4 ), ppem );
+ }
+
+ /* Convert darken_amount from per 1000 em to true character space. */
+ return af_fixedToInt( FT_DivFix( darken_amount, em_ratio ) );
+ }
+
+
/* END */
diff --git a/src/autofit/afloader.h b/src/autofit/afloader.h
index 37cfd14..4c4affc 100644
--- a/src/autofit/afloader.h
+++ b/src/autofit/afloader.h
@@ -75,6 +75,11 @@ FT_BEGIN_HEADER
FT_UInt gindex,
FT_Int32 load_flags );
+ FT_LOCAL_DEF( FT_Int32 )
+ af_loader_compute_darkening( AF_Loader loader,
+ FT_Face face,
+ FT_Pos standard_width );
+
/* */