1 files changed, 110 insertions, 0 deletions
diff --git a/vendor/github.com/golang/freetype/example/round/main.go b/vendor/github.com/golang/freetype/example/round/main.go
new file mode 100644
index 000000000..2920e8335
--- /dev/null
+++ b/vendor/github.com/golang/freetype/example/round/main.go
@@ -0,0 +1,110 @@
+// Copyright 2010 The Freetype-Go Authors. All rights reserved.
+// Use of this source code is governed by your choice of either the
+// FreeType License or the GNU General Public License version 2 (or
+// any later version), both of which can be found in the LICENSE file.
+
+// +build example
+//
+// This build tag means that "go install github.com/golang/freetype/..."
+// doesn't install this example program. Use "go run main.go" to run it or "go
+// install -tags=example" to install it.
+
+// This program visualizes the quadratic approximation to the circle, used to
+// implement round joins when stroking paths. The approximation is used in the
+// stroking code for arcs between 0 and 45 degrees, but is visualized here
+// between 0 and 90 degrees. The discrepancy between the approximation and the
+// true circle is clearly visible at angles above 65 degrees.
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"image"
+	"image/color"
+	"image/draw"
+	"image/png"
+	"log"
+	"math"
+	"os"
+
+	"github.com/golang/freetype/raster"
+	"golang.org/x/image/math/fixed"
+)
+
+// pDot returns the dot product p·q.
+func pDot(p, q fixed.Point26_6) fixed.Int52_12 {
+	px, py := int64(p.X), int64(p.Y)
+	qx, qy := int64(q.X), int64(q.Y)
+	return fixed.Int52_12(px*qx + py*qy)
+}
+
+func main() {
+	const (
+		n = 17
+		r = 64 * 80
+	)
+	s := fixed.Int26_6(r * math.Sqrt(2) / 2)
+	t := fixed.Int26_6(r * math.Tan(math.Pi/8))
+
+	m := image.NewRGBA(image.Rect(0, 0, 800, 600))
+	draw.Draw(m, m.Bounds(), image.NewUniform(color.RGBA{63, 63, 63, 255}), image.ZP, draw.Src)
+	mp := raster.NewRGBAPainter(m)
+	mp.SetColor(image.Black)
+	z := raster.NewRasterizer(800, 600)
+
+	for i := 0; i < n; i++ {
+		cx := fixed.Int26_6(6400 + 12800*(i%4))
+		cy := fixed.Int26_6(640 + 8000*(i/4))
+		c := fixed.Point26_6{X: cx, Y: cy}
+		theta := math.Pi * (0.5 + 0.5*float64(i)/(n-1))
+		dx := fixed.Int26_6(r * math.Cos(theta))
+		dy := fixed.Int26_6(r * math.Sin(theta))
+		d := fixed.Point26_6{X: dx, Y: dy}
+		// Draw a quarter-circle approximated by two quadratic segments,
+		// with each segment spanning 45 degrees.
+		z.Start(c)
+		z.Add1(c.Add(fixed.Point26_6{X: r, Y: 0}))
+		z.Add2(c.Add(fixed.Point26_6{X: r, Y: t}), c.Add(fixed.Point26_6{X: s, Y: s}))
+		z.Add2(c.Add(fixed.Point26_6{X: t, Y: r}), c.Add(fixed.Point26_6{X: 0, Y: r}))
+		// Add another quadratic segment whose angle ranges between 0 and 90
+		// degrees. For an explanation of the magic constants 128, 150, 181 and
+		// 256, read the comments in the freetype/raster package.
+		dot := 256 * pDot(d, fixed.Point26_6{X: 0, Y: r}) / (r * r)
+		multiple := fixed.Int26_6(150-(150-128)*(dot-181)/(256-181)) >> 2
+		z.Add2(c.Add(fixed.Point26_6{X: dx, Y: r + dy}.Mul(multiple)), c.Add(d))
+		// Close the curve.
+		z.Add1(c)
+	}
+	z.Rasterize(mp)
+
+	for i := 0; i < n; i++ {
+		cx := fixed.Int26_6(6400 + 12800*(i%4))
+		cy := fixed.Int26_6(640 + 8000*(i/4))
+		for j := 0; j < n; j++ {
+			theta := math.Pi * float64(j) / (n - 1)
+			dx := fixed.Int26_6(r * math.Cos(theta))
+			dy := fixed.Int26_6(r * math.Sin(theta))
+			m.Set(int((cx+dx)/64), int((cy+dy)/64), color.RGBA{255, 255, 0, 255})
+		}
+	}
+
+	// Save that RGBA image to disk.
+	outFile, err := os.Create("out.png")
+	if err != nil {
+		log.Println(err)
+		os.Exit(1)
+	}
+	defer outFile.Close()
+	b := bufio.NewWriter(outFile)
+	err = png.Encode(b, m)
+	if err != nil {
+		log.Println(err)
+		os.Exit(1)
+	}
+	err = b.Flush()
+	if err != nil {
+		log.Println(err)
+		os.Exit(1)
+	}
+	fmt.Println("Wrote out.png OK.")
+}