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Diffstat (limited to 'vendor/github.com/golang/freetype/example/round/main.go')
-rw-r--r-- | vendor/github.com/golang/freetype/example/round/main.go | 110 |
1 files changed, 0 insertions, 110 deletions
diff --git a/vendor/github.com/golang/freetype/example/round/main.go b/vendor/github.com/golang/freetype/example/round/main.go deleted file mode 100644 index 2920e8335..000000000 --- a/vendor/github.com/golang/freetype/example/round/main.go +++ /dev/null @@ -1,110 +0,0 @@ -// 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.") -} |