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Diffstat (limited to 'Godeps/_workspace/src/code.google.com/p/freetype-go/example/round/main.go')
-rw-r--r-- | Godeps/_workspace/src/code.google.com/p/freetype-go/example/round/main.go | 96 |
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.") +} |