1 files changed, 96 insertions, 0 deletions
diff --git a/Godeps/_workspace/src/code.google.com/p/freetype-go/example/round/main.go b/Godeps/_workspace/src/code.google.com/p/freetype-go/example/round/main.go
new file mode 100644
index 000000000..e2435f9a2
--- /dev/null
+++ b/Godeps/_workspace/src/code.google.com/p/freetype-go/example/round/main.go
@@ -0,0 +1,96 @@
+// 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.
+
+// 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"
+
+	"code.google.com/p/freetype-go/freetype/raster"
+)
+
+func main() {
+	const (
+		n = 17
+		r = 256 * 80
+	)
+	s := raster.Fix32(r * math.Sqrt(2) / 2)
+	t := raster.Fix32(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 := raster.Fix32(25600 + 51200*(i%4))
+		cy := raster.Fix32(2560 + 32000*(i/4))
+		c := raster.Point{X: cx, Y: cy}
+		theta := math.Pi * (0.5 + 0.5*float64(i)/(n-1))
+		dx := raster.Fix32(r * math.Cos(theta))
+		dy := raster.Fix32(r * math.Sin(theta))
+		d := raster.Point{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(raster.Point{X: r, Y: 0}))
+		z.Add2(c.Add(raster.Point{X: r, Y: t}), c.Add(raster.Point{X: s, Y: s}))
+		z.Add2(c.Add(raster.Point{X: t, Y: r}), c.Add(raster.Point{X: 0, Y: r}))
+		// Add another quadratic segment whose angle ranges between 0 and 90 degrees.
+		// For an explanation of the magic constants 22, 150, 181 and 256, read the
+		// comments in the freetype/raster package.
+		dot := 256 * d.Dot(raster.Point{X: 0, Y: r}) / (r * r)
+		multiple := raster.Fix32(150 - 22*(dot-181)/(256-181))
+		z.Add2(c.Add(raster.Point{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 := raster.Fix32(25600 + 51200*(i%4))
+		cy := raster.Fix32(2560 + 32000*(i/4))
+		for j := 0; j < n; j++ {
+			theta := math.Pi * float64(j) / (n - 1)
+			dx := raster.Fix32(r * math.Cos(theta))
+			dy := raster.Fix32(r * math.Sin(theta))
+			m.Set(int((cx+dx)/256), int((cy+dy)/256), color.RGBA{255, 255, 0, 255})
+		}
+	}
+
+	// Save that RGBA image to disk.
+	f, err := os.Create("out.png")
+	if err != nil {
+		log.Println(err)
+		os.Exit(1)
+	}
+	defer f.Close()
+	b := bufio.NewWriter(f)
+	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.")
+}