[Git][freetype/freetype][master] [sfnt] Clarify `COLR` v1 FT_Paint* format representations

[Werner Lemberg (@wl)]

Werner Lemberg pushed to branch master at FreeType / FreeType

Commits:

• d3d3ff76
  by Dominik Röttsches at 2021-11-03T08:28:10+00:00

  [sfnt] Clarify `COLR` v1 FT_Paint* format representations
  
  * include/freetype/ftcolor.h (FT_PaintLinearGradient,
  FT_PaintRadialGradient, FT_PaintSweepGradient, FT_PaintTransform,
  FT_PaintTranslate, FT_PaintScale, FT_PaintRotate, FT_PaintSkew): Clarify
  16.16 fixed point representation of struct fields.
  * src/sfnt/ttcolr.c (read_paint): Shift coordinates for
  FT_PaintLinearGradient, FT_PaintRadialGradient, FT_PaintSweepGradient
  accordingly.
  
  Fixes: https://gitlab.freedesktop.org/freetype/freetype/-/issues/1110
  

2 changed files:

• include/freetype/ftcolor.h
• src/sfnt/ttcolr.c

Changes:

include/freetype/ftcolor.h

---

...	...	@@ -870,13 +870,16 @@ FT_BEGIN_HEADER
870	870	* color stops along the gradient.
871	871	*
872	872	* p0 ::
873		- * The starting point of the gradient definition (in font units).
	873	+ * The starting point of the gradient definition in font units
	874	+ * represented as a 16.16 fixed-point `FT_Vector`.
874	875	*
875	876	* p1 ::
876		- * The end point of the gradient definition (in font units).
	877	+ * The end point of the gradient definition in font units
	878	+ * represented as a 16.16 fixed-point `FT_Vector`.
877	879	*
878	880	* p2 ::
879		- * Optional point~p2 to rotate the gradient (in font units).
	881	+ * Optional point~p2 to rotate the gradient in font units
	882	+ * represented as a 16.16 fixed-point `FT_Vector`.
880	883	* Otherwise equal to~p0.
881	884	*
882	885	* @since:
...	...	@@ -914,19 +917,20 @@ FT_BEGIN_HEADER
914	917	* color stops along the gradient.
915	918	*
916	919	* c0 ::
917		- * The center of the starting point of the radial gradient (in font
918		- * units).
	920	+ * The center of the starting point of the radial gradient in font
	921	+ * units represented as a 16.16 fixed-point `FT_Vector`.
919	922	*
920	923	* r0 ::
921		- * The radius of the starting circle of the radial gradient (in font
922		- * units).
	924	+ * The radius of the starting circle of the radial gradient in font
	925	+ * units represented as a 16.16 fixed-point value.
923	926	*
924	927	* c1 ::
925		- * The center of the end point of the radial gradient (in font units).
	928	+ * The center of the end point of the radial gradient in font units
	929	+ * represented as a 16.16 fixed-point `FT_Vector`.
926	930	*
927	931	* r1 ::
928		- * The radius of the end circle of the radial gradient (in font
929		- * units).
	932	+ * The radius of the end circle of the radial gradient in font
	933	+ * units represented as a 16.16 fixed-point value.
930	934	*
931	935	* @since:
932	936	* 2.11 -- **currently experimental only!** There might be changes
...	...	@@ -938,9 +942,9 @@ FT_BEGIN_HEADER
938	942	FT_ColorLine colorline;
939	943
940	944	FT_Vector c0;
941		- FT_UShort r0;
	945	+ FT_Pos r0;
942	946	FT_Vector c1;
943		- FT_UShort r1;
	947	+ FT_Pos r1;
944	948
945	949	} FT_PaintRadialGradient;
946	950
...	...	@@ -963,16 +967,17 @@ FT_BEGIN_HEADER
963	967	* color stops along the gradient.
964	968	*
965	969	* center ::
966		- * The center of the sweep gradient (in font units).
	970	+ * The center of the sweep gradient in font units represented as a
	971	+ * vector of 16.16 fixed-point values.
967	972	*
968	973	* start_angle ::
969		- * The start angle of the sweep gradient, in 16.16 fixed point
	974	+ * The start angle of the sweep gradient in 16.16 fixed-point
970	975	* format specifying degrees divided by 180.0 (as in the
971	976	* spec). Multiply by 180.0f to receive degrees value. Values are
972	977	* given counter-clockwise, starting from the (positive) y~axis.
973	978	*
974	979	* end_angle ::
975		- * The end angle of the sweep gradient, in 16.16 fixed point
	980	+ * The end angle of the sweep gradient in 16.16 fixed-point
976	981	* format specifying degrees divided by 180.0 (as in the
977	982	* spec). Multiply by 180.0f to receive degrees value. Values are
978	983	* given counter-clockwise, starting from the (positive) y~axis.
...	...	@@ -1061,7 +1066,8 @@ FT_BEGIN_HEADER
1061	1066	* An opaque paint that is subject to being transformed.
1062	1067	*
1063	1068	* affine ::
1064		- * A 2x3 transformation matrix in @FT_Affine23 format.
	1069	+ * A 2x3 transformation matrix in @FT_Affine23 format containing
	1070	+ * 16.16 fixed-point values.
1065	1071	*
1066	1072	* @since:
1067	1073	* 2.11 -- **currently experimental only!** There might be changes
...	...	@@ -1091,10 +1097,12 @@ FT_BEGIN_HEADER
1091	1097	* rotated.
1092	1098	*
1093	1099	* dx ::
1094		- * Translation in x~direction (in font units).
	1100	+ * Translation in x~direction in font units represented as a
	1101	+ * 16.16 fixed-point value.
1095	1102	*
1096	1103	* dy ::
1097		- * Translation in y~direction (in font units).
	1104	+ * Translation in y~direction in font units represented as a
	1105	+ * 16.16 fixed-point value.
1098	1106	*
1099	1107	* @since:
1100	1108	* 2.11 -- **currently experimental only!** There might be changes
...	...	@@ -1132,16 +1140,20 @@ FT_BEGIN_HEADER
1132	1140	* scaled.
1133	1141	*
1134	1142	* scale_x ::
1135		- * Scale factor in x~direction.
	1143	+ * Scale factor in x~direction represented as a
	1144	+ * 16.16 fixed-point value.
1136	1145	*
1137	1146	* scale_y ::
1138		- * Scale factor in y~direction.
	1147	+ * Scale factor in y~direction represented as a
	1148	+ * 16.16 fixed-point value.
1139	1149	*
1140	1150	* center_x ::
1141		- * x~coordinate of center point to scale from.
	1151	+ * x~coordinate of center point to scale from represented as a
	1152	+ * 16.16 fixed-point value.
1142	1153	*
1143	1154	* center_y ::
1144		- * y~coordinate of center point to scale from.
	1155	+ * y~coordinate of center point to scale from represented as a
	1156	+ * 16.16 fixed-point value.
1145	1157	*
1146	1158	* @since:
1147	1159	* 2.11 -- **currently experimental only!** There might be changes
...	...	@@ -1177,16 +1189,16 @@ FT_BEGIN_HEADER
1177	1189	*
1178	1190	* angle ::
1179	1191	* The rotation angle that is to be applied in degrees divided by
1180		- * 180.0 (as in the spec). Multiply by 180.0f to receive degrees
1181		- * value.
	1192	+ * 180.0 (as in the spec) represented as a 16.16 fixed-point
	1193	+ * value. Multiply by 180.0f to receive degrees value.
1182	1194	*
1183	1195	* center_x ::
1184		- * The x~coordinate of the pivot point of the rotation (in font
1185		- * units).
	1196	+ * The x~coordinate of the pivot point of the rotation in font
	1197	+ * units) represented as a 16.16 fixed-point value.
1186	1198	*
1187	1199	* center_y ::
1188		- * The y~coordinate of the pivot point of the rotation (in font
1189		- * units).
	1200	+ * The y~coordinate of the pivot point of the rotation in font
	1201	+ * units represented as a 16.16 fixed-point value.
1190	1202	*
1191	1203	* @since:
1192	1204	* 2.11 -- **currently experimental only!** There might be changes
...	...	@@ -1223,17 +1235,21 @@ FT_BEGIN_HEADER
1223	1235	*
1224	1236	* x_skew_angle ::
1225	1237	* The skewing angle in x~direction in degrees divided by 180.0
1226		- * (as in the spec). Multiply by 180.0f to receive degrees.
	1238	+ * (as in the spec) represented as a 16.16 fixed-point
	1239	+ * value. Multiply by 180.0f to receive degrees.
1227	1240	*
1228	1241	* y_skew_angle ::
1229	1242	* The skewing angle in y~direction in degrees divided by 180.0
1230		- * (as in the spec). Multiply by 180.0f to receive degrees.
	1243	+ * (as in the spec) represented as a 16.16 fixed-point
	1244	+ * value. Multiply by 180.0f to receive degrees.
1231	1245	*
1232	1246	* center_x ::
1233		- * The x~coordinate of the pivot point of the skew (in font units).
	1247	+ * The x~coordinate of the pivot point of the skew in font units
	1248	+ * represented as a 16.16 fixed-point value.
1234	1249	*
1235	1250	* center_y ::
1236		- * The y~coordinate of the pivot point of the skew (in font units).
	1251	+ * The y~coordinate of the pivot point of the skew in font units
	1252	+ * represented as a 16.16 fixed-point value.
1237	1253	*
1238	1254	* @since:
1239	1255	* 2.11 -- **currently experimental only!** There might be changes

src/sfnt/ttcolr.c

---

...	...	@@ -505,12 +505,16 @@
505	505	&apaint->u.linear_gradient.colorline ) )
506	506	return 0;
507	507
508		- apaint->u.linear_gradient.p0.x = FT_NEXT_SHORT( p );
509		- apaint->u.linear_gradient.p0.y = FT_NEXT_SHORT( p );
510		- apaint->u.linear_gradient.p1.x = FT_NEXT_SHORT( p );
511		- apaint->u.linear_gradient.p1.y = FT_NEXT_SHORT( p );
512		- apaint->u.linear_gradient.p2.x = FT_NEXT_SHORT( p );
513		- apaint->u.linear_gradient.p2.y = FT_NEXT_SHORT( p );
	508	+ /*
	509	+ * In order to support variations expose these as FT_Fixed 16.16 values so
	510	+ * that we can support fractional values after interpolation.
	511	+ */
	512	+ apaint->u.linear_gradient.p0.x = FT_NEXT_SHORT( p ) << 16;
	513	+ apaint->u.linear_gradient.p0.y = FT_NEXT_SHORT( p ) << 16;
	514	+ apaint->u.linear_gradient.p1.x = FT_NEXT_SHORT( p ) << 16;
	515	+ apaint->u.linear_gradient.p1.y = FT_NEXT_SHORT( p ) << 16;
	516	+ apaint->u.linear_gradient.p2.x = FT_NEXT_SHORT( p ) << 16;
	517	+ apaint->u.linear_gradient.p2.y = FT_NEXT_SHORT( p ) << 16;
514	518
515	519	return 1;
516	520	}
...	...	@@ -521,15 +525,15 @@
521	525	&apaint->u.radial_gradient.colorline ) )
522	526	return 0;
523	527
524		- apaint->u.radial_gradient.c0.x = FT_NEXT_SHORT( p );
525		- apaint->u.radial_gradient.c0.y = FT_NEXT_SHORT( p );
	528	+ apaint->u.radial_gradient.c0.x = FT_NEXT_SHORT( p ) << 16;
	529	+ apaint->u.radial_gradient.c0.y = FT_NEXT_SHORT( p ) << 16;
526	530
527		- apaint->u.radial_gradient.r0 = FT_NEXT_USHORT( p );
	531	+ apaint->u.radial_gradient.r0 = FT_NEXT_USHORT( p ) << 16;
528	532
529		- apaint->u.radial_gradient.c1.x = FT_NEXT_SHORT( p );
530		- apaint->u.radial_gradient.c1.y = FT_NEXT_SHORT( p );
	533	+ apaint->u.radial_gradient.c1.x = FT_NEXT_SHORT( p ) << 16;
	534	+ apaint->u.radial_gradient.c1.y = FT_NEXT_SHORT( p ) << 16;
531	535
532		- apaint->u.radial_gradient.r1 = FT_NEXT_USHORT( p );
	536	+ apaint->u.radial_gradient.r1 = FT_NEXT_USHORT( p ) << 16;
533	537
534	538	return 1;
535	539	}
...	...	@@ -540,8 +544,8 @@
540	544	&apaint->u.sweep_gradient.colorline ) )
541	545	return 0;
542	546
543		- apaint->u.sweep_gradient.center.x = FT_NEXT_SHORT( p );
544		- apaint->u.sweep_gradient.center.y = FT_NEXT_SHORT( p );
	547	+ apaint->u.sweep_gradient.center.x = FT_NEXT_SHORT( p ) << 16;
	548	+ apaint->u.sweep_gradient.center.y = FT_NEXT_SHORT( p ) << 16;
545	549
546	550	apaint->u.sweep_gradient.start_angle = FT_NEXT_SHORT( p ) << 2;
547	551	apaint->u.sweep_gradient.end_angle = FT_NEXT_SHORT( p ) << 2;
...	...	@@ -568,6 +572,10 @@
568	572
569	573	p = child_table_p;
570	574
	575	+ /*
	576	+ * The following matrix coefficients are encoded as
	577	+ * OpenType 16.16 fixed-point values.
	578	+ */
571	579	apaint->u.transform.affine.xx = FT_NEXT_LONG( p );
572	580	apaint->u.transform.affine.yx = FT_NEXT_LONG( p );
573	581	apaint->u.transform.affine.xy = FT_NEXT_LONG( p );

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