[font] expose COLR API

Author: benoitkugler

font/color.go

@@ -0,0 +1,37 @@
+package font
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/go-text/typesetting/font/opentype/tables"
+)
+
+// Support for COLR and CPAL tables
+
+// CPAL is the 'CPAL' table,
+// with [numPalettes]x[numPaletteEntries] colors.
+// CPAL[0] is the default palette
+type CPAL [][]tables.ColorRecord
+
+func newCPAL(table tables.CPAL) (CPAL, error) {
+	numPalettes := len(table.ColorRecordIndices)
+	numColors := len(table.ColorRecordsArray)
+
+	// "The first palette, palette index 0, is the default palette.
+	// A minimum of one palette must be provided in the CPAL table if the table is present.
+	// Palettes must have a minimum of one color record. An empty CPAL table,
+	// with no palettes and no color records is not permitted."
+	if numPalettes == 0 {
+		return nil, errors.New("empty CPAL table")
+	}
+	out := make(CPAL, numPalettes)
+	for i, startIndex := range table.ColorRecordIndices {
+		endIndex := int(startIndex) + int(table.NumPaletteEntries)
+		if endIndex > numColors {
+			return nil, fmt.Errorf("invalid CPAL table (expected at least %d colors, got %d)", endIndex, numColors)
+		}
+		out[i] = table.ColorRecordsArray[startIndex:endIndex]
+	}
+	return out, nil
+}

font/font.go

@@ -154,6 +154,9 @@ type Font struct {
 	bitmap bitmap
 	sbix   sbix
 
+	COLR *tables.COLR1 // color glyphs, optional
+	CPAL CPAL          // color glyphs, optional
+
 	os2   os2
 	names tables.Name
 	head  tables.Head
@@ -267,6 +270,18 @@ func NewFont(ld *ot.Loader) (*Font, error) {
 	svg, _, _ := tables.ParseSVG(raw)
 	out.svg, _ = newSvg(svg)
 
+	raw, _ = ld.RawTable(ot.MustNewTag("COLR"))
+	if colr, err := tables.ParseCOLR(raw); err == nil {
+		out.COLR = &colr
+		// color table without CPAL is broken
+		raw, _ = ld.RawTable(ot.MustNewTag("CPAL"))
+		cpal, _, _ := tables.ParseCPAL(raw)
+		out.CPAL, err = newCPAL(cpal)
+		if err != nil {
+			return nil, err
+		}
+	}
+
 	out.hhea, out.hmtx, _ = loadHmtx(ld, out.nGlyphs)
 	out.vhea, out.vmtx, _ = loadVmtx(ld, out.nGlyphs)
 

font/font_test.go

@@ -134,3 +134,15 @@ func TestCapHeight(t *testing.T) {
 	tu.Assert(t, face.LineMetric(CapHeight) == 730)
 	tu.Assert(t, face.LineMetric(XHeight) == 520)
 }
+
+func TestLoadColor(t *testing.T) {
+	ld := readFontFile(t, "color/NotoColorEmoji-Regular.ttf")
+	ft, err := NewFont(ld)
+	tu.AssertNoErr(t, err)
+	tu.Assert(t, ft.COLR != nil && ft.CPAL != nil)
+
+	ld = readFontFile(t, "color/CoralPixels-Regular.ttf")
+	ft, err = NewFont(ld)
+	tu.AssertNoErr(t, err)
+	tu.Assert(t, ft.COLR != nil && ft.CPAL != nil)
+}

font/opentype/tables/glyphs.go

@@ -15,3 +15,9 @@ type EBLC = CBLC
 // Bloc is the bitmap location table
 // See - https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6bloc.html
 type Bloc = CBLC
+
+// PaintColrLayersResolved is a simili PaintTable, build
+// from COLR version 0 table.
+type PaintColrLayersResolved []Layer
+
+func (PaintColrLayersResolved) isPaintTable() {}

font/opentype/tables/glyphs_color_test.go

@@ -10,44 +10,67 @@ func TestCOLR(t *testing.T) {
 	ft := readFontFile(t, "color/NotoColorEmoji-Regular.ttf")
 	colr, err := ParseCOLR(readTable(t, ft, "COLR"))
 	tu.AssertNoErr(t, err)
-	tu.Assert(t, len(colr.BaseGlyphRecords) == 0)
-	tu.Assert(t, len(colr.LayerRecords) == 0)
-	tu.Assert(t, len(colr.BaseGlyphList.PaintRecords) == 3845)
-	tu.Assert(t, colr.BaseGlyphList.PaintRecords[0].Paint == PaintColrLayers{1, 3, 47625})
-	tu.Assert(t, colr.ClipList.Clips[0].ClipBox == ClipBoxFormat1{1, 480, 192, 800, 512})
+	tu.Assert(t, len(colr.baseGlyphRecords) == 0)
+	tu.Assert(t, len(colr.layerRecords) == 0)
+	tu.Assert(t, len(colr.baseGlyphList.paintRecords) == 3845)
+	tu.Assert(t, colr.baseGlyphList.paintRecords[0].Paint == PaintColrLayers{1, 3, 47625})
+	tu.Assert(t, colr.ClipList.clips[0].ClipBox == ClipBoxFormat1{1, 480, 192, 800, 512})
 	tu.Assert(t, colr.VarIndexMap == nil && colr.ItemVariationStore == nil)
-	tu.Assert(t, len(colr.LayerList.PaintTables) == 69264)
+	tu.Assert(t, len(colr.LayerList.paintTables) == 69264)
+
+	clipBox, ok := colr.ClipList.Search(87)
+	tu.Assert(t, ok && clipBox == ClipBoxFormat1{1, 64, -224, 1216, 928})
 
 	// reference from fonttools
-	paint := colr.LayerList.PaintTables[6]
+	paint := colr.LayerList.paintTables[6]
 	transform, ok := paint.(PaintTransform)
 	tu.Assert(t, ok)
 	_, innerOK := transform.Paint.(PaintGlyph)
 	tu.Assert(t, transform.Transform == Affine2x3{1, 0, 0, 1, 4.3119965, 0.375})
 	tu.Assert(t, innerOK)
 
+	pt, ok := colr.Search(12)
+	asColrLayers, ok2 := pt.(PaintColrLayers)
+	tu.Assert(t, ok && ok2)
+	tu.Assert(t, asColrLayers == PaintColrLayers{1, 9, 2427})
+
+	for _, paint := range colr.baseGlyphList.paintRecords {
+		if layers, ok := paint.Paint.(PaintColrLayers); ok {
+			l, err := colr.LayerList.Resolve(layers)
+			tu.AssertNoErr(t, err)
+			tu.Assert(t, len(l) == int(layers.NumLayers))
+		}
+	}
+
 	ft = readFontFile(t, "color/CoralPixels-Regular.ttf")
 	colr, err = ParseCOLR(readTable(t, ft, "COLR"))
 	tu.AssertNoErr(t, err)
-	tu.Assert(t, len(colr.BaseGlyphRecords) == 335)
-	tu.Assert(t, len(colr.LayerRecords) == 5603)
-	g1, g2 := colr.BaseGlyphRecords[0], colr.BaseGlyphRecords[1]
-	tu.Assert(t, g1 == BaseGlyph{0, 0, 11} && g2 == BaseGlyph{2, 11, 18})
-	tu.Assert(t, colr.LayerRecords[0].PaletteIndex == 4)
+	tu.Assert(t, len(colr.baseGlyphRecords) == 335)
+	tu.Assert(t, len(colr.layerRecords) == 5603)
+	g1, g2 := colr.baseGlyphRecords[0], colr.baseGlyphRecords[1]
+	tu.Assert(t, g1 == baseGlyph{0, 0, 11} && g2 == baseGlyph{2, 11, 18})
+	tu.Assert(t, colr.layerRecords[0].PaletteIndex == 4)
+
+	pt, ok = colr.Search(0)
+	asLayers, ok2 := pt.(PaintColrLayersResolved)
+	tu.Assert(t, ok && ok2)
+	tu.Assert(t, len(asLayers) == 11)
+	tu.Assert(t, asLayers[0].PaletteIndex == 4)
+	tu.Assert(t, asLayers[10].PaletteIndex == 11)
 }
 
 func TestCPAL(t *testing.T) {
 	ft := readFontFile(t, "color/NotoColorEmoji-Regular.ttf")
 	cpal, _, err := ParseCPAL(readTable(t, ft, "CPAL"))
 	tu.AssertNoErr(t, err)
 	tu.Assert(t, cpal.Version == 0)
-	tu.Assert(t, cpal.numPaletteEntries == 5921)
+	tu.Assert(t, cpal.NumPaletteEntries == 5921)
 	tu.Assert(t, cpal.numPalettes == 1 && len(cpal.ColorRecordIndices) == 1)
 
 	ft = readFontFile(t, "color/CoralPixels-Regular.ttf")
 	cpal, _, err = ParseCPAL(readTable(t, ft, "CPAL"))
 	tu.AssertNoErr(t, err)
 	tu.Assert(t, cpal.Version == 0)
-	tu.Assert(t, cpal.numPaletteEntries == 32)
+	tu.Assert(t, cpal.NumPaletteEntries == 32)
 	tu.Assert(t, cpal.numPalettes == 2 && len(cpal.ColorRecordIndices) == 2)
 }