[Git][freetype/freetype][master] [sfnt] Add API for retrieving a 'COLR' v1 'ClipBox' table.

[Werner Lemberg (@wl)]

Werner Lemberg pushed to branch master at FreeType / FreeType

Commits:

• 47cf8ebf
  by Dominik Röttsches at 2021-08-07T14:44:05+02:00

  [sfnt] Add API for retrieving a 'COLR' v1 'ClipBox' table.
  
  The optional 'COLR' v1 glyph-specific clip box helps upstream graphics
  libraries allocate a sufficiently large bitmap for a glyph without having to
  traverse the glyph graph for that.  See
  
    https://github.com/googlefonts/colr-gradients-spec/issues/251
  
  for background on the introduction of this specification change.
  
  * include/freetype/ftcolor.h (FT_ClipBox): New structure.
  (FT_Get_Color_Glyph_ClipBox): New function declaration.
  
  * include/freetype/internal/sfnt.h (TT_Get_Color_Glyph_ClipBox_Func):
  New function type.
  (SFNT_Interface, FT_DEFINE_SFNT_INTERFACE): Use it.
  
  * src/base/ftobjs.c (FT_Get_Color_Glyph_ClipBox): New function to link API
  with SFNT implementation.
  
  * src/sfnt/sfdriver.c (sfnt_interface): Updated.
  * src/sfnt/ttcolr.c (Colr): New field `clip_list`.
  (tt_face_load_colr): Parse global clip list offset.
  (tt_face_get_color_glyph_clipbox): New function to find the clip box for a
  glyph id from the clip list array.
  * src/sfnt/ttcolr.h: Updated.
  

6 changed files:

• include/freetype/ftcolor.h
• include/freetype/internal/sfnt.h
• src/base/ftobjs.c
• src/sfnt/sfdriver.c
• src/sfnt/ttcolr.c
• src/sfnt/ttcolr.h

Changes:

include/freetype/ftcolor.h

---

...	...	@@ -1383,6 +1383,49 @@ FT_BEGIN_HEADER
1383	1383	} FT_Color_Root_Transform;
1384	1384
1385	1385
	1386	+ /**************************************************************************
	1387	+ *
	1388	+ * @struct:
	1389	+ * FT_ClipBox
	1390	+ *
	1391	+ * @description:
	1392	+ * A structure representing a 'COLR' v1 'ClipBox' table. 'COLR' v1
	1393	+ * glyphs may optionally define a clip box for aiding allocation or
	1394	+ * defining a maximum drawable region. Use @FT_Get_Color_Glyph_ClipBox
	1395	+ * to retrieve it.
	1396	+ *
	1397	+ * @fields:
	1398	+ * bottom_left ::
	1399	+ * The bottom left corner of the clip box as an @FT_Vector with
	1400	+ * fixed-point coordinates in 26.6 format.
	1401	+ *
	1402	+ * top_left ::
	1403	+ * The top left corner of the clip box as an @FT_Vector with
	1404	+ * fixed-point coordinates in 26.6 format.
	1405	+ *
	1406	+ * top_right ::
	1407	+ * The top right corner of the clip box as an @FT_Vector with
	1408	+ * fixed-point coordinates in 26.6 format.
	1409	+ *
	1410	+ * bottom_right ::
	1411	+ * The bottom right corner of the clip box as an @FT_Vector with
	1412	+ * fixed-point coordinates in 26.6 format.
	1413	+ *
	1414	+ * @since:
	1415	+ * 2.12 -- **currently experimental only!** There might be changes
	1416	+ * without retaining backward compatibility of both the API and ABI.
	1417	+ *
	1418	+ */
	1419	+ typedef struct FT_ClipBox_
	1420	+ {
	1421	+ FT_Vector bottom_left;
	1422	+ FT_Vector top_left;
	1423	+ FT_Vector top_right;
	1424	+ FT_Vector bottom_right;
	1425	+
	1426	+ } FT_ClipBox;
	1427	+
	1428	+
1386	1429	/**************************************************************************
1387	1430	*
1388	1431	* @function:
...	...	@@ -1475,6 +1518,49 @@ FT_BEGIN_HEADER
1475	1518	FT_OpaquePaint* paint );
1476	1519
1477	1520
	1521	+ /**************************************************************************
	1522	+ *
	1523	+ * @function:
	1524	+ * FT_Get_Color_Glyph_ClipBox
	1525	+ *
	1526	+ * @description:
	1527	+ * Search for a 'COLR' v1 clip box for the specified `base_glyph` and
	1528	+ * fill the `clip_box` parameter with the 'COLR' v1 'ClipBox' information
	1529	+ * if one is found.
	1530	+ *
	1531	+ * @input:
	1532	+ * face ::
	1533	+ * A handle to the parent face object.
	1534	+ *
	1535	+ * base_glyph ::
	1536	+ * The glyph index for which to retrieve the clip box.
	1537	+ *
	1538	+ * @output:
	1539	+ * clip_box ::
	1540	+ * The clip box for the requested `base_glyph` if one is found. The
	1541	+ * clip box is computed taking scale and transformations configured on
	1542	+ * the @FT_Face into account. @FT_ClipBox contains @FT_Vector values
	1543	+ * in 26.6 format.
	1544	+ *
	1545	+ * @return:
	1546	+ * Value~1 if a clip box is found. If no clip box is found or an error
	1547	+ * occured, value~0 is returned.
	1548	+ *
	1549	+ * @note:
	1550	+ * To retrieve the clip box in font units, reset scale to units-per-em
	1551	+ * and remove transforms configured using @FT_Set_Transform.
	1552	+ *
	1553	+ * @since:
	1554	+ * 2.12 -- **currently experimental only!** There might be changes
	1555	+ * without retaining backward compatibility of both the API and ABI.
	1556	+ *
	1557	+ */
	1558	+ FT_EXPORT( FT_Bool )
	1559	+ FT_Get_Color_Glyph_ClipBox( FT_Face face,
	1560	+ FT_UInt base_glyph,
	1561	+ FT_ClipBox* clip_box );
	1562	+
	1563	+
1478	1564	/**************************************************************************
1479	1565	*
1480	1566	* @function:

include/freetype/internal/sfnt.h

---

...	...	@@ -555,6 +555,44 @@ FT_BEGIN_HEADER
555	555	FT_OpaquePaint *paint );
556	556
557	557
	558	+ /**************************************************************************
	559	+ *
	560	+ * @functype:
	561	+ * TT_Get_Color_Glyph_ClipBox_Func
	562	+ *
	563	+ * @description:
	564	+ * Search for a 'COLR' v1 clip box for the specified `base_glyph` and
	565	+ * fill the `clip_box` parameter with the 'COLR' v1 'ClipBox' information
	566	+ * if one is found.
	567	+ *
	568	+ * @input:
	569	+ * face ::
	570	+ * A handle to the parent face object.
	571	+ *
	572	+ * base_glyph ::
	573	+ * The glyph index for which to retrieve the clip box.
	574	+ *
	575	+ * @output:
	576	+ * clip_box ::
	577	+ * The clip box for the requested base_glyph if one is found. The clip
	578	+ * box is computed taking scale and transformations configured on the
	579	+ * @FT_Face into account. @FT_ClipBox contains @FT_Vector values in
	580	+ * 26.6 format.
	581	+ *
	582	+ * @note:
	583	+ * To retrieve the clip box in font units, reset scale to units-per-em
	584	+ * and remove transforms configured using @FT_Set_Transform.
	585	+ *
	586	+ * @return:
	587	+ * Value~1 if a ClipBox is found. If no clip box is found or an
	588	+ * error occured, value~0 is returned.
	589	+ */
	590	+ typedef FT_Bool
	591	+ ( *TT_Get_Color_Glyph_ClipBox_Func )( TT_Face face,
	592	+ FT_UInt base_glyph,
	593	+ FT_ClipBox* clip_box );
	594	+
	595	+
558	596	/**************************************************************************
559	597	*
560	598	* @functype:
...	...	@@ -890,17 +928,18 @@ FT_BEGIN_HEADER
890	928	TT_Set_SBit_Strike_Func set_sbit_strike;
891	929	TT_Load_Strike_Metrics_Func load_strike_metrics;
892	930
893		- TT_Load_Table_Func load_cpal;
894		- TT_Load_Table_Func load_colr;
895		- TT_Free_Table_Func free_cpal;
896		- TT_Free_Table_Func free_colr;
897		- TT_Set_Palette_Func set_palette;
898		- TT_Get_Colr_Layer_Func get_colr_layer;
899		- TT_Get_Color_Glyph_Paint_Func get_colr_glyph_paint;
900		- TT_Get_Paint_Layers_Func get_paint_layers;
901		- TT_Get_Colorline_Stops_Func get_colorline_stops;
902		- TT_Get_Paint_Func get_paint;
903		- TT_Blend_Colr_Func colr_blend;
	931	+ TT_Load_Table_Func load_cpal;
	932	+ TT_Load_Table_Func load_colr;
	933	+ TT_Free_Table_Func free_cpal;
	934	+ TT_Free_Table_Func free_colr;
	935	+ TT_Set_Palette_Func set_palette;
	936	+ TT_Get_Colr_Layer_Func get_colr_layer;
	937	+ TT_Get_Color_Glyph_Paint_Func get_colr_glyph_paint;
	938	+ TT_Get_Color_Glyph_ClipBox_Func get_color_glyph_clipbox;
	939	+ TT_Get_Paint_Layers_Func get_paint_layers;
	940	+ TT_Get_Colorline_Stops_Func get_colorline_stops;
	941	+ TT_Get_Paint_Func get_paint;
	942	+ TT_Blend_Colr_Func colr_blend;
904	943
905	944	TT_Get_Metrics_Func get_metrics;
906	945
...	...	@@ -951,6 +990,7 @@ FT_BEGIN_HEADER
951	990	set_palette_, \
952	991	get_colr_layer_, \
953	992	get_colr_glyph_paint_, \
	993	+ get_color_glyph_clipbox, \
954	994	get_paint_layers_, \
955	995	get_colorline_stops_, \
956	996	get_paint_, \
...	...	@@ -995,6 +1035,7 @@ FT_BEGIN_HEADER
995	1035	set_palette_, \
996	1036	get_colr_layer_, \
997	1037	get_colr_glyph_paint_, \
	1038	+ get_color_glyph_clipbox, \
998	1039	get_paint_layers_, \
999	1040	get_colorline_stops_, \
1000	1041	get_paint_, \

src/base/ftobjs.c

---

...	...	@@ -5639,6 +5639,35 @@
5639	5639	}
5640	5640
5641	5641
	5642	+ /* documentation is in ftcolor.h */
	5643	+
	5644	+ FT_EXPORT_DEF( FT_Bool )
	5645	+ FT_Get_Color_Glyph_ClipBox( FT_Face face,
	5646	+ FT_UInt base_glyph,
	5647	+ FT_ClipBox* clip_box )
	5648	+ {
	5649	+ TT_Face ttface;
	5650	+ SFNT_Service sfnt;
	5651	+
	5652	+
	5653	+ if ( !face || !clip_box )
	5654	+ return 0;
	5655	+
	5656	+ if ( !FT_IS_SFNT( face ) )
	5657	+ return 0;
	5658	+
	5659	+ ttface = (TT_Face)face;
	5660	+ sfnt = (SFNT_Service)ttface->sfnt;
	5661	+
	5662	+ if ( sfnt->get_color_glyph_clipbox )
	5663	+ return sfnt->get_color_glyph_clipbox( ttface,
	5664	+ base_glyph,
	5665	+ clip_box );
	5666	+ else
	5667	+ return 0;
	5668	+ }
	5669	+
	5670	+
5642	5671	/* documentation is in freetype.h */
5643	5672
5644	5673	FT_EXPORT_DEF( FT_Bool )

src/sfnt/sfdriver.c

---

...	...	@@ -1292,13 +1292,15 @@
1292	1292	/* TT_Get_Colr_Layer_Func get_colr_layer */
1293	1293
1294	1294	PUT_COLOR_LAYERS_V1( tt_face_get_colr_glyph_paint ),
1295		- /* TT_Get_Colr_Glyph_Paint_Func get_colr_glyph_paint */
	1295	+ /* TT_Get_Color_Glyph_Paint_Func get_colr_glyph_paint */
	1296	+ PUT_COLOR_LAYERS_V1( tt_face_get_color_glyph_clipbox ),
	1297	+ /* TT_Get_Color_Glyph_ClipBox_Func get_clipbox */
1296	1298	PUT_COLOR_LAYERS_V1( tt_face_get_paint_layers ),
1297		- /* TT_Get_Paint_Layers_Func get_paint_layers */
	1299	+ /* TT_Get_Paint_Layers_Func get_paint_layers */
1298	1300	PUT_COLOR_LAYERS_V1( tt_face_get_colorline_stops ),
1299		- /* TT_Get_Paint get_paint */
	1301	+ /* TT_Get_Paint get_paint */
1300	1302	PUT_COLOR_LAYERS_V1( tt_face_get_paint ),
1301		- /* TT_Get_Colorline_Stops_Func get_colorline_stops */
	1303	+ /* TT_Get_Colorline_Stops_Func get_colorline_stops */
1302	1304
1303	1305	PUT_COLOR_LAYERS( tt_face_colr_blend_layer ),
1304	1306	/* TT_Blend_Colr_Func colr_blend */

src/sfnt/ttcolr.c

---

...	...	@@ -94,6 +94,8 @@
94	94	FT_ULong num_layers_v1;
95	95	FT_Byte* layers_v1;
96	96
	97	+ FT_Byte* clip_list;
	98	+
97	99	/*
98	100	* Paint tables start at the minimum of the end of the LayerList and the
99	101	* end of the BaseGlyphList. Record this location in a field here for
...	...	@@ -134,7 +136,7 @@
134	136
135	137	FT_ULong base_glyph_offset, layer_offset;
136	138	FT_ULong base_glyphs_offset_v1, num_base_glyphs_v1;
137		- FT_ULong layer_offset_v1, num_layers_v1;
	139	+ FT_ULong layer_offset_v1, num_layers_v1, clip_list_offset;
138	140	FT_ULong table_size;
139	141
140	142
...	...	@@ -226,6 +228,16 @@
226	228	colr->base_glyphs_v1 +
227	229	colr->num_base_glyphs_v1 * BASE_GLYPH_PAINT_RECORD_SIZE;
228	230	}
	231	+
	232	+ clip_list_offset = FT_NEXT_ULONG( p );
	233	+
	234	+ if ( clip_list_offset >= table_size )
	235	+ goto InvalidTable;
	236	+
	237	+ if ( clip_list_offset )
	238	+ colr->clip_list = (FT_Byte*)( table + clip_list_offset );
	239	+ else
	240	+ colr->clip_list = 0;
229	241	}
230	242
231	243	colr->base_glyphs = (FT_Byte*)( table + base_glyph_offset );
...	...	@@ -796,6 +808,117 @@
796	808	}
797	809
798	810
	811	+ FT_LOCAL_DEF( FT_Bool )
	812	+ tt_face_get_color_glyph_clipbox( TT_Face face,
	813	+ FT_UInt base_glyph,
	814	+ FT_ClipBox* clip_box )
	815	+ {
	816	+ Colr* colr;
	817	+
	818	+ FT_Byte *p, *p1, *clip_base;
	819	+
	820	+ FT_Byte clip_list_format;
	821	+ FT_ULong num_clip_boxes, i;
	822	+ FT_UShort gid_start, gid_end;
	823	+ FT_UInt32 clip_box_offset;
	824	+ FT_Byte format;
	825	+
	826	+ const FT_Byte num_corners = 4;
	827	+ FT_Vector corners[4];
	828	+ FT_Byte j;
	829	+ FT_BBox font_clip_box;
	830	+
	831	+
	832	+ colr = (Colr*)face->colr;
	833	+ if ( !colr )
	834	+ return 0;
	835	+
	836	+ if ( !colr->clip_list )
	837	+ return 0;
	838	+
	839	+ p = colr->clip_list;
	840	+
	841	+ clip_base = p;
	842	+ clip_list_format = FT_NEXT_BYTE ( p );
	843	+
	844	+ /* Format byte used here to be able to upgrade ClipList for >16bit */
	845	+ /* glyph ids; for now we can expect it to be 0. */
	846	+ if ( !( clip_list_format == 0 ) )
	847	+ return 0;
	848	+
	849	+ num_clip_boxes = FT_NEXT_ULONG( p );
	850	+
	851	+ for ( i = 0; i < num_clip_boxes; ++i )
	852	+ {
	853	+ gid_start = FT_NEXT_USHORT( p );
	854	+ gid_end = FT_NEXT_USHORT( p );
	855	+ clip_box_offset = FT_NEXT_UOFF3( p );
	856	+
	857	+ if ( base_glyph >= gid_start && base_glyph <= gid_end )
	858	+ {
	859	+ p1 = (FT_Byte*)( clip_base + clip_box_offset );
	860	+
	861	+ if ( p1 >= ( (FT_Byte*)colr->table + colr->table_size ) )
	862	+ return 0;
	863	+
	864	+ format = FT_NEXT_BYTE( p1 );
	865	+
	866	+ if ( format < 0 || format > 1 )
	867	+ return 0;
	868	+
	869	+ /* `face->root.size->metrics.x_scale` and `y_scale` are factors */
	870	+ /* that scale a font unit value in integers to a 26.6 fixed value */
	871	+ /* according to the requested size, see for example */
	872	+ /* `ft_recompute_scaled_metrics`. */
	873	+ font_clip_box.xMin = FT_MulFix( FT_NEXT_SHORT( p1 ),
	874	+ face->root.size->metrics.x_scale );
	875	+ font_clip_box.yMin = FT_MulFix( FT_NEXT_SHORT( p1 ),
	876	+ face->root.size->metrics.x_scale );
	877	+ font_clip_box.xMax = FT_MulFix( FT_NEXT_SHORT( p1 ),
	878	+ face->root.size->metrics.x_scale );
	879	+ font_clip_box.yMax = FT_MulFix( FT_NEXT_SHORT( p1 ),
	880	+ face->root.size->metrics.x_scale );
	881	+
	882	+ /* Make 4 corner points (xMin, yMin), (xMax, yMax) and transform */
	883	+ /* them. If we we would only transform two corner points and */
	884	+ /* span a rectangle based on those, the rectangle may become too */
	885	+ /* small to cover the glyph. */
	886	+ corners[0].x = font_clip_box.xMin;
	887	+ corners[1].x = font_clip_box.xMin;
	888	+ corners[2].x = font_clip_box.xMax;
	889	+ corners[3].x = font_clip_box.xMax;
	890	+
	891	+ corners[0].y = font_clip_box.yMin;
	892	+ corners[1].y = font_clip_box.yMax;
	893	+ corners[2].y = font_clip_box.yMax;
	894	+ corners[3].y = font_clip_box.yMin;
	895	+
	896	+ for ( j = 0; j < num_corners; ++j )
	897	+ {
	898	+ if ( face->root.internal->transform_flags & 1 )
	899	+ FT_Vector_Transform( &corners[j],
	900	+ &face->root.internal->transform_matrix );
	901	+
	902	+ if ( face->root.internal->transform_flags & 2 )
	903	+ {
	904	+ corners[j].x += face->root.internal->transform_delta.x;
	905	+ corners[j].y += face->root.internal->transform_delta.y;
	906	+ }
	907	+ }
	908	+
	909	+ clip_box->bottom_left = corners[0];
	910	+ clip_box->top_left = corners[1];
	911	+ clip_box->top_right = corners[2];
	912	+ clip_box->bottom_right = corners[3];
	913	+
	914	+ return 1;
	915	+ }
	916	+ }
	917	+
	918	+ return 0;
	919	+ }
	920	+
	921	+
799	922	FT_LOCAL_DEF( FT_Bool )
800	923	tt_face_get_paint_layers( TT_Face face,
801	924	FT_LayerIterator* iterator,

src/sfnt/ttcolr.h

---

...	...	@@ -48,6 +48,11 @@ FT_BEGIN_HEADER
48	48	FT_Color_Root_Transform root_transform,
49	49	FT_OpaquePaint* paint );
50	50
	51	+ FT_LOCAL( FT_Bool )
	52	+ tt_face_get_color_glyph_clipbox( TT_Face face,
	53	+ FT_UInt base_glyph,
	54	+ FT_ClipBox* clip_box );
	55	+
51	56	FT_LOCAL( FT_Bool )
52	57	tt_face_get_paint_layers( TT_Face face,
53	58	FT_LayerIterator* iterator,

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