ref: 47cf8ebf4a78ed42da455a98d77a92ce6a180d78
parent: 6be8bfe499fcb4f8de989d5d977b0433877b7271
author: Dominik Röttsches <[email protected]>
date: Wed Jul 28 13:36:57 EDT 2021
[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.
--- a/include/freetype/ftcolor.h
+++ b/include/freetype/ftcolor.h
@@ -1385,6 +1385,49 @@
/**************************************************************************
*
+ * @struct:
+ * FT_ClipBox
+ *
+ * @description:
+ * A structure representing a 'COLR' v1 'ClipBox' table. 'COLR' v1
+ * glyphs may optionally define a clip box for aiding allocation or
+ * defining a maximum drawable region. Use @FT_Get_Color_Glyph_ClipBox
+ * to retrieve it.
+ *
+ * @fields:
+ * bottom_left ::
+ * The bottom left corner of the clip box as an @FT_Vector with
+ * fixed-point coordinates in 26.6 format.
+ *
+ * top_left ::
+ * The top left corner of the clip box as an @FT_Vector with
+ * fixed-point coordinates in 26.6 format.
+ *
+ * top_right ::
+ * The top right corner of the clip box as an @FT_Vector with
+ * fixed-point coordinates in 26.6 format.
+ *
+ * bottom_right ::
+ * The bottom right corner of the clip box as an @FT_Vector with
+ * fixed-point coordinates in 26.6 format.
+ *
+ * @since:
+ * 2.12 -- **currently experimental only!** There might be changes
+ * without retaining backward compatibility of both the API and ABI.
+ *
+ */
+ typedef struct FT_ClipBox_
+ {+ FT_Vector bottom_left;
+ FT_Vector top_left;
+ FT_Vector top_right;
+ FT_Vector bottom_right;
+
+ } FT_ClipBox;
+
+
+ /**************************************************************************
+ *
* @function:
* FT_Get_Color_Glyph_Paint
*
@@ -1473,6 +1516,49 @@
FT_UInt base_glyph,
FT_Color_Root_Transform root_transform,
FT_OpaquePaint* paint );
+
+
+ /**************************************************************************
+ *
+ * @function:
+ * FT_Get_Color_Glyph_ClipBox
+ *
+ * @description:
+ * Search for a 'COLR' v1 clip box for the specified `base_glyph` and
+ * fill the `clip_box` parameter with the 'COLR' v1 'ClipBox' information
+ * if one is found.
+ *
+ * @input:
+ * face ::
+ * A handle to the parent face object.
+ *
+ * base_glyph ::
+ * The glyph index for which to retrieve the clip box.
+ *
+ * @output:
+ * clip_box ::
+ * The clip box for the requested `base_glyph` if one is found. The
+ * clip box is computed taking scale and transformations configured on
+ * the @FT_Face into account. @FT_ClipBox contains @FT_Vector values
+ * in 26.6 format.
+ *
+ * @return:
+ * Value~1 if a clip box is found. If no clip box is found or an error
+ * occured, value~0 is returned.
+ *
+ * @note:
+ * To retrieve the clip box in font units, reset scale to units-per-em
+ * and remove transforms configured using @FT_Set_Transform.
+ *
+ * @since:
+ * 2.12 -- **currently experimental only!** There might be changes
+ * without retaining backward compatibility of both the API and ABI.
+ *
+ */
+ FT_EXPORT( FT_Bool )
+ FT_Get_Color_Glyph_ClipBox( FT_Face face,
+ FT_UInt base_glyph,
+ FT_ClipBox* clip_box );
/**************************************************************************
--- a/include/freetype/internal/sfnt.h
+++ b/include/freetype/internal/sfnt.h
@@ -558,6 +558,44 @@
/**************************************************************************
*
* @functype:
+ * TT_Get_Color_Glyph_ClipBox_Func
+ *
+ * @description:
+ * Search for a 'COLR' v1 clip box for the specified `base_glyph` and
+ * fill the `clip_box` parameter with the 'COLR' v1 'ClipBox' information
+ * if one is found.
+ *
+ * @input:
+ * face ::
+ * A handle to the parent face object.
+ *
+ * base_glyph ::
+ * The glyph index for which to retrieve the clip box.
+ *
+ * @output:
+ * clip_box ::
+ * The clip box for the requested base_glyph if one is found. The clip
+ * box is computed taking scale and transformations configured on the
+ * @FT_Face into account. @FT_ClipBox contains @FT_Vector values in
+ * 26.6 format.
+ *
+ * @note:
+ * To retrieve the clip box in font units, reset scale to units-per-em
+ * and remove transforms configured using @FT_Set_Transform.
+ *
+ * @return:
+ * Value~1 if a ClipBox is found. If no clip box is found or an
+ * error occured, value~0 is returned.
+ */
+ typedef FT_Bool
+ ( *TT_Get_Color_Glyph_ClipBox_Func )( TT_Face face,
+ FT_UInt base_glyph,
+ FT_ClipBox* clip_box );
+
+
+ /**************************************************************************
+ *
+ * @functype:
* TT_Get_Paint_Layers_Func
*
* @description:
@@ -890,17 +928,18 @@
TT_Set_SBit_Strike_Func set_sbit_strike;
TT_Load_Strike_Metrics_Func load_strike_metrics;
- TT_Load_Table_Func load_cpal;
- TT_Load_Table_Func load_colr;
- TT_Free_Table_Func free_cpal;
- TT_Free_Table_Func free_colr;
- TT_Set_Palette_Func set_palette;
- TT_Get_Colr_Layer_Func get_colr_layer;
- TT_Get_Color_Glyph_Paint_Func get_colr_glyph_paint;
- TT_Get_Paint_Layers_Func get_paint_layers;
- TT_Get_Colorline_Stops_Func get_colorline_stops;
- TT_Get_Paint_Func get_paint;
- TT_Blend_Colr_Func colr_blend;
+ TT_Load_Table_Func load_cpal;
+ TT_Load_Table_Func load_colr;
+ TT_Free_Table_Func free_cpal;
+ TT_Free_Table_Func free_colr;
+ TT_Set_Palette_Func set_palette;
+ TT_Get_Colr_Layer_Func get_colr_layer;
+ TT_Get_Color_Glyph_Paint_Func get_colr_glyph_paint;
+ TT_Get_Color_Glyph_ClipBox_Func get_color_glyph_clipbox;
+ TT_Get_Paint_Layers_Func get_paint_layers;
+ TT_Get_Colorline_Stops_Func get_colorline_stops;
+ TT_Get_Paint_Func get_paint;
+ TT_Blend_Colr_Func colr_blend;
TT_Get_Metrics_Func get_metrics;
@@ -951,6 +990,7 @@
set_palette_, \
get_colr_layer_, \
get_colr_glyph_paint_, \
+ get_color_glyph_clipbox, \
get_paint_layers_, \
get_colorline_stops_, \
get_paint_, \
@@ -995,6 +1035,7 @@
set_palette_, \
get_colr_layer_, \
get_colr_glyph_paint_, \
+ get_color_glyph_clipbox, \
get_paint_layers_, \
get_colorline_stops_, \
get_paint_, \
--- a/src/base/ftobjs.c
+++ b/src/base/ftobjs.c
@@ -5639,6 +5639,35 @@
}
+ /* documentation is in ftcolor.h */
+
+ FT_EXPORT_DEF( FT_Bool )
+ FT_Get_Color_Glyph_ClipBox( FT_Face face,
+ FT_UInt base_glyph,
+ FT_ClipBox* clip_box )
+ {+ TT_Face ttface;
+ SFNT_Service sfnt;
+
+
+ if ( !face || !clip_box )
+ return 0;
+
+ if ( !FT_IS_SFNT( face ) )
+ return 0;
+
+ ttface = (TT_Face)face;
+ sfnt = (SFNT_Service)ttface->sfnt;
+
+ if ( sfnt->get_color_glyph_clipbox )
+ return sfnt->get_color_glyph_clipbox( ttface,
+ base_glyph,
+ clip_box );
+ else
+ return 0;
+ }
+
+
/* documentation is in freetype.h */
FT_EXPORT_DEF( FT_Bool )
--- a/src/sfnt/sfdriver.c
+++ b/src/sfnt/sfdriver.c
@@ -1292,13 +1292,15 @@
/* TT_Get_Colr_Layer_Func get_colr_layer */
PUT_COLOR_LAYERS_V1( tt_face_get_colr_glyph_paint ),
- /* TT_Get_Colr_Glyph_Paint_Func get_colr_glyph_paint */
+ /* TT_Get_Color_Glyph_Paint_Func get_colr_glyph_paint */
+ PUT_COLOR_LAYERS_V1( tt_face_get_color_glyph_clipbox ),
+ /* TT_Get_Color_Glyph_ClipBox_Func get_clipbox */
PUT_COLOR_LAYERS_V1( tt_face_get_paint_layers ),
- /* TT_Get_Paint_Layers_Func get_paint_layers */
+ /* TT_Get_Paint_Layers_Func get_paint_layers */
PUT_COLOR_LAYERS_V1( tt_face_get_colorline_stops ),
- /* TT_Get_Paint get_paint */
+ /* TT_Get_Paint get_paint */
PUT_COLOR_LAYERS_V1( tt_face_get_paint ),
- /* TT_Get_Colorline_Stops_Func get_colorline_stops */
+ /* TT_Get_Colorline_Stops_Func get_colorline_stops */
PUT_COLOR_LAYERS( tt_face_colr_blend_layer ),
/* TT_Blend_Colr_Func colr_blend */
--- a/src/sfnt/ttcolr.c
+++ b/src/sfnt/ttcolr.c
@@ -94,6 +94,8 @@
FT_ULong num_layers_v1;
FT_Byte* layers_v1;
+ FT_Byte* clip_list;
+
/*
* Paint tables start at the minimum of the end of the LayerList and the
* end of the BaseGlyphList. Record this location in a field here for
@@ -134,7 +136,7 @@
FT_ULong base_glyph_offset, layer_offset;
FT_ULong base_glyphs_offset_v1, num_base_glyphs_v1;
- FT_ULong layer_offset_v1, num_layers_v1;
+ FT_ULong layer_offset_v1, num_layers_v1, clip_list_offset;
FT_ULong table_size;
@@ -226,6 +228,16 @@
colr->base_glyphs_v1 +
colr->num_base_glyphs_v1 * BASE_GLYPH_PAINT_RECORD_SIZE;
}
+
+ clip_list_offset = FT_NEXT_ULONG( p );
+
+ if ( clip_list_offset >= table_size )
+ goto InvalidTable;
+
+ if ( clip_list_offset )
+ colr->clip_list = (FT_Byte*)( table + clip_list_offset );
+ else
+ colr->clip_list = 0;
}
colr->base_glyphs = (FT_Byte*)( table + base_glyph_offset );
@@ -793,6 +805,117 @@
opaque_paint->insert_root_transform = 0;
return 1;
+ }
+
+
+ FT_LOCAL_DEF( FT_Bool )
+ tt_face_get_color_glyph_clipbox( TT_Face face,
+ FT_UInt base_glyph,
+ FT_ClipBox* clip_box )
+ {+ Colr* colr;
+
+ FT_Byte *p, *p1, *clip_base;
+
+ FT_Byte clip_list_format;
+ FT_ULong num_clip_boxes, i;
+ FT_UShort gid_start, gid_end;
+ FT_UInt32 clip_box_offset;
+ FT_Byte format;
+
+ const FT_Byte num_corners = 4;
+ FT_Vector corners[4];
+ FT_Byte j;
+ FT_BBox font_clip_box;
+
+
+ colr = (Colr*)face->colr;
+ if ( !colr )
+ return 0;
+
+ if ( !colr->clip_list )
+ return 0;
+
+ p = colr->clip_list;
+
+ clip_base = p;
+ clip_list_format = FT_NEXT_BYTE ( p );
+
+ /* Format byte used here to be able to upgrade ClipList for >16bit */
+ /* glyph ids; for now we can expect it to be 0. */
+ if ( !( clip_list_format == 0 ) )
+ return 0;
+
+ num_clip_boxes = FT_NEXT_ULONG( p );
+
+ for ( i = 0; i < num_clip_boxes; ++i )
+ {+ gid_start = FT_NEXT_USHORT( p );
+ gid_end = FT_NEXT_USHORT( p );
+ clip_box_offset = FT_NEXT_UOFF3( p );
+
+ if ( base_glyph >= gid_start && base_glyph <= gid_end )
+ {+ p1 = (FT_Byte*)( clip_base + clip_box_offset );
+
+ if ( p1 >= ( (FT_Byte*)colr->table + colr->table_size ) )
+ return 0;
+
+ format = FT_NEXT_BYTE( p1 );
+
+ if ( format < 0 || format > 1 )
+ return 0;
+
+ /* `face->root.size->metrics.x_scale` and `y_scale` are factors */
+ /* that scale a font unit value in integers to a 26.6 fixed value */
+ /* according to the requested size, see for example */
+ /* `ft_recompute_scaled_metrics`. */
+ font_clip_box.xMin = FT_MulFix( FT_NEXT_SHORT( p1 ),
+ face->root.size->metrics.x_scale );
+ font_clip_box.yMin = FT_MulFix( FT_NEXT_SHORT( p1 ),
+ face->root.size->metrics.x_scale );
+ font_clip_box.xMax = FT_MulFix( FT_NEXT_SHORT( p1 ),
+ face->root.size->metrics.x_scale );
+ font_clip_box.yMax = FT_MulFix( FT_NEXT_SHORT( p1 ),
+ face->root.size->metrics.x_scale );
+
+ /* Make 4 corner points (xMin, yMin), (xMax, yMax) and transform */
+ /* them. If we we would only transform two corner points and */
+ /* span a rectangle based on those, the rectangle may become too */
+ /* small to cover the glyph. */
+ corners[0].x = font_clip_box.xMin;
+ corners[1].x = font_clip_box.xMin;
+ corners[2].x = font_clip_box.xMax;
+ corners[3].x = font_clip_box.xMax;
+
+ corners[0].y = font_clip_box.yMin;
+ corners[1].y = font_clip_box.yMax;
+ corners[2].y = font_clip_box.yMax;
+ corners[3].y = font_clip_box.yMin;
+
+ for ( j = 0; j < num_corners; ++j )
+ {+ if ( face->root.internal->transform_flags & 1 )
+ FT_Vector_Transform( &corners[j],
+ &face->root.internal->transform_matrix );
+
+ if ( face->root.internal->transform_flags & 2 )
+ {+ corners[j].x += face->root.internal->transform_delta.x;
+ corners[j].y += face->root.internal->transform_delta.y;
+ }
+ }
+
+ clip_box->bottom_left = corners[0];
+ clip_box->top_left = corners[1];
+ clip_box->top_right = corners[2];
+ clip_box->bottom_right = corners[3];
+
+ return 1;
+ }
+ }
+
+ return 0;
}
--- a/src/sfnt/ttcolr.h
+++ b/src/sfnt/ttcolr.h
@@ -49,6 +49,11 @@
FT_OpaquePaint* paint );
FT_LOCAL( FT_Bool )
+ tt_face_get_color_glyph_clipbox( TT_Face face,
+ FT_UInt base_glyph,
+ FT_ClipBox* clip_box );
+
+ FT_LOCAL( FT_Bool )
tt_face_get_paint_layers( TT_Face face,
FT_LayerIterator* iterator,
FT_OpaquePaint* paint );