Example_rotation gives some examples of rotating text.
()
| 18 | |
| 19 | // Example_rotation gives some examples of rotating text. |
| 20 | func Example_rotation() { |
| 21 | n := 100 |
| 22 | xmax := 2 * math.Pi |
| 23 | |
| 24 | // Sin creates a sine curve. |
| 25 | sin := func(n int, xmax float64) plotter.XYs { |
| 26 | xy := make(plotter.XYs, n) |
| 27 | for i := range n { |
| 28 | xy[i].X = xmax / float64(n) * float64(i) |
| 29 | xy[i].Y = math.Sin(xy[i].X) * 100 |
| 30 | } |
| 31 | return xy |
| 32 | } |
| 33 | |
| 34 | // These points will make up our sine curve. |
| 35 | linePoints := sin(n, xmax) |
| 36 | |
| 37 | // These points are our label locations. |
| 38 | labelPoints := sin(8, xmax) |
| 39 | |
| 40 | p := plot.New() |
| 41 | p.Title.Text = "Rotation Example" |
| 42 | p.X.Label.Text = "X" |
| 43 | p.Y.Label.Text = "100 × Sine X" |
| 44 | |
| 45 | l, err := plotter.NewLine(linePoints) |
| 46 | if err != nil { |
| 47 | log.Panic(err) |
| 48 | } |
| 49 | l.LineStyle.Width = vg.Points(1) |
| 50 | l.LineStyle.Color = color.RGBA{B: 255, A: 255} |
| 51 | |
| 52 | labelData := plotter.XYLabels{ |
| 53 | XYs: labelPoints, |
| 54 | Labels: []string{"0", "pi/4", "pi/2", "3pi/4", "pi", "5pi/4", "3pi/2", "7pi/4", "2pi"}, |
| 55 | } |
| 56 | |
| 57 | labels, err := plotter.NewLabels(labelData) |
| 58 | if err != nil { |
| 59 | log.Panic(err) |
| 60 | } |
| 61 | |
| 62 | for i := range labels.TextStyle { |
| 63 | x := labels.XYs[i].X |
| 64 | |
| 65 | // Set the label rotation to the slope of the line, so the label is |
| 66 | // parallel with the line. |
| 67 | labels.TextStyle[i].Rotation = math.Atan(math.Cos(x)) |
| 68 | labels.TextStyle[i].XAlign = draw.XCenter |
| 69 | labels.TextStyle[i].YAlign = draw.YCenter |
| 70 | // Move the labels away from the line so they're more easily readable. |
| 71 | if x >= math.Pi { |
| 72 | labels.TextStyle[i].YAlign = draw.YTop |
| 73 | } else { |
| 74 | labels.TextStyle[i].YAlign = draw.YBottom |
| 75 | } |
| 76 | } |
| 77 |