add examples/vectorfont

Updates #1937

examples/fontvector/main.go

@@ -0,0 +1,160 @@
+// Copyright 2022 The Ebitengine Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"image"
+	"image/color"
+	"log"
+	"math"
+
+	"golang.org/x/image/font"
+	"golang.org/x/image/font/sfnt"
+	"golang.org/x/image/math/fixed"
+
+	"github.com/hajimehoshi/ebiten/v2"
+	"github.com/hajimehoshi/ebiten/v2/examples/resources/fonts"
+	"github.com/hajimehoshi/ebiten/v2/vector"
+)
+
+var (
+	whiteImage = ebiten.NewImage(3, 3)
+
+	// whiteSubImage is an internal sub image of whiteImage.
+	// Use whiteSubImage at DrawTriangles instead of whiteImage in order to avoid bleeding edges.
+	whiteSubImage = whiteImage.SubImage(image.Rect(1, 1, 2, 2)).(*ebiten.Image)
+)
+
+func init() {
+	whiteImage.Fill(color.White)
+}
+
+const (
+	screenWidth  = 640
+	screenHeight = 480
+)
+
+func fixed26_6ToFloat32(x fixed.Int26_6) float32 {
+	return float32(x>>6) + float32(x&((1<<6)-1))/float32(1<<6)
+}
+
+type Game struct {
+	segments sfnt.Segments
+	bounds   fixed.Rectangle26_6
+	vertices []ebiten.Vertex
+	indices  []uint16
+
+	tick int
+}
+
+func (g *Game) Update() error {
+	g.tick++
+
+	if g.segments == nil {
+		ppem := fixed.I(300)
+
+		f, err := sfnt.Parse(fonts.MPlus1pRegular_ttf)
+		if err != nil {
+			return err
+		}
+
+		var b sfnt.Buffer
+		idx, err := f.GlyphIndex(&b, 'あ')
+		if err != nil {
+			return err
+		}
+
+		segments, err := f.LoadGlyph(&b, idx, ppem, nil)
+		if err != nil {
+			return err
+		}
+		g.segments = segments
+
+		bounds, err := f.Bounds(&b, ppem, font.HintingNone)
+		if err != nil {
+			return err
+		}
+		g.bounds = bounds
+	}
+	return nil
+}
+
+func (g *Game) Draw(screen *ebiten.Image) {
+	var path vector.Path
+	for _, seg := range g.segments {
+		switch seg.Op {
+		case sfnt.SegmentOpMoveTo:
+			path.MoveTo(
+				fixed26_6ToFloat32(seg.Args[0].X),
+				fixed26_6ToFloat32(seg.Args[0].Y),
+			)
+		case sfnt.SegmentOpLineTo:
+			path.LineTo(
+				fixed26_6ToFloat32(seg.Args[0].X),
+				fixed26_6ToFloat32(seg.Args[0].Y),
+			)
+		case sfnt.SegmentOpQuadTo:
+			path.QuadTo(
+				fixed26_6ToFloat32(seg.Args[0].X),
+				fixed26_6ToFloat32(seg.Args[0].Y),
+				fixed26_6ToFloat32(seg.Args[1].X),
+				fixed26_6ToFloat32(seg.Args[1].Y),
+			)
+		case sfnt.SegmentOpCubeTo:
+			path.CubicTo(
+				fixed26_6ToFloat32(seg.Args[0].X),
+				fixed26_6ToFloat32(seg.Args[0].Y),
+				fixed26_6ToFloat32(seg.Args[1].X),
+				fixed26_6ToFloat32(seg.Args[1].Y),
+				fixed26_6ToFloat32(seg.Args[2].X),
+				fixed26_6ToFloat32(seg.Args[2].Y),
+			)
+		}
+	}
+	path.Close()
+
+	g.vertices = g.vertices[:0]
+	g.indices = g.indices[:0]
+
+	op := &vector.StrokeOptions{}
+	op.Width = 3 * (float32(math.Sin(float64(g.tick)*2*math.Pi/180)) + 1)
+	op.LineJoin = vector.LineJoinRound
+	op.LineCap = vector.LineCapRound
+	g.vertices, g.indices = path.AppendVerticesAndIndicesForStroke(g.vertices, g.indices, op)
+
+	for i := range g.vertices {
+		g.vertices[i].DstX += screenWidth/2 - fixed26_6ToFloat32(g.bounds.Max.X+g.bounds.Min.X)/2
+		g.vertices[i].DstY += screenHeight/2 - fixed26_6ToFloat32(g.bounds.Max.Y+g.bounds.Min.Y)/2
+		g.vertices[i].SrcX = 1
+		g.vertices[i].SrcY = 1
+	}
+
+	{
+		op := &ebiten.DrawTrianglesOptions{}
+		op.AntiAlias = true
+		screen.DrawTriangles(g.vertices, g.indices, whiteSubImage, op)
+	}
+}
+
+func (*Game) Layout(width, height int) (int, int) {
+	return screenWidth, screenHeight
+}
+
+func main() {
+	ebiten.SetWindowTitle("Font Vector (Ebitengine Demo)")
+	if err := ebiten.RunGame(&Game{}); err != nil {
+		log.Fatal(err)
+	}
+}