[font] support EBDT bitmap Format 1

Closes #244

Author: benoitkugler

font/bitmaps.go

@@ -429,10 +429,10 @@ func parseBitmapDataMetrics(imageData []byte, start, end tables.Offset32, imageF
 	}
 	imageData = imageData[start:end]
 	switch imageFormat {
-	case 1, 6, 7, 8, 9:
+	case 6, 7, 8, 9:
 		return bitmapImage{}, fmt.Errorf("valid but currently not implemented bitmap image format: %d", imageFormat)
-	case 2:
-		data, _, err := tables.ParseBitmapData2(imageData)
+	case 1, 2:
+		data, _, err := tables.ParseBitmapData1or2(imageData)
 		return bitmapImage{metrics: data.SmallGlyphMetrics, image: data.Image}, err
 	case 17:
 		data, _, err := tables.ParseBitmapData17(imageData)

font/bitmaps_test.go

@@ -3,6 +3,7 @@
 package font
 
 import (
+	"bytes"
 	"testing"
 
 	td "github.com/go-text/typesetting-utils/opentype"
@@ -50,3 +51,15 @@ func TestEBLC(t *testing.T) {
 		tu.AssertNoErr(t, err)
 	}
 }
+
+func TestEBDTFormat1(t *testing.T) {
+	file, err := td.Files.ReadFile("bitmap/simsun.ttc")
+	tu.AssertNoErr(t, err)
+
+	faces, err := ParseTTC(bytes.NewReader(file))
+	tu.AssertNoErr(t, err)
+	tu.Assert(t, len(faces) == 2)
+	sizes := faces[0].BitmapSizes()
+	tu.Assert(t, len(sizes) == 6)
+	tu.Assert(t, sizes[0].XPpem == 12 && sizes[5].XPpem == 17)
+}

font/opentype/tables/glyphs_bitmap_gen.go

@@ -161,8 +161,9 @@ type BigGlyphMetrics struct {
 	vertAdvance  uint8 // Vertical advance width in pixels.
 }
 
+// Format 1: small metrics, byte-aligned data
 // Format 2: small metrics, bit-aligned data
-type BitmapData2 struct {
+type BitmapData1or2 struct {
 	SmallGlyphMetrics
 	Image []byte `arrayCount:"ToEnd"`
 }

font/opentype/tables/glyphs_bitmap_src.go

@@ -3,7 +3,7 @@ module github.com/go-text/typesetting
 go 1.19
 
 require (
-	github.com/go-text/typesetting-utils v0.0.0-20260223113751-2d88ac90dae3
+	github.com/go-text/typesetting-utils v0.0.0-20260327125527-fbf04b32d9ad
 	golang.org/x/image v0.23.0
 	golang.org/x/text v0.21.0
 )

go.mod

@@ -1,5 +1,5 @@
-github.com/go-text/typesetting-utils v0.0.0-20260223113751-2d88ac90dae3 h1:drBZzMgdYPbmyXqOto4YhhJGrFIQCX94FpR4MzTCsos=
-github.com/go-text/typesetting-utils v0.0.0-20260223113751-2d88ac90dae3/go.mod h1:3/62I4La/HBRX9TcTpBj4eipLiwzf+vhI+7whTc9V7o=
+github.com/go-text/typesetting-utils v0.0.0-20260327125527-fbf04b32d9ad h1:J6fi06yzug4KkyQo0hK7UZVFBIlCh7iaG38sGq7THaY=
+github.com/go-text/typesetting-utils v0.0.0-20260327125527-fbf04b32d9ad/go.mod h1:3/62I4La/HBRX9TcTpBj4eipLiwzf+vhI+7whTc9V7o=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=