// Approximate a circular arc using multiple // cubic Bézier curves, one for each π/2 segment. // // This is from: // http://hansmuller-flex.blogspot.com/2011/04/approximating-circular-arc-with-cubic.html func arc(p *pdf.Path, comp vg.PathComp) { x0 := comp.X + comp.Radius*vg.Length(math.Cos(comp.Start)) y0 := comp.Y + comp.Radius*vg.Length(math.Sin(comp.Start)) p.Line(pdfPoint(x0, y0)) a1 := comp.Start end := a1 + comp.Angle sign := 1.0 if end < a1 { sign = -1.0 } left := math.Abs(comp.Angle) // Square root of the machine epsilon for IEEE 64-bit floating // point values. This is the equality threshold recommended // in Numerical Recipes, if I recall correctly—it's small enough. const epsilon = 1.4901161193847656e-08 for left > epsilon { a2 := a1 + sign*math.Min(math.Pi/2, left) partialArc(p, comp.X, comp.Y, comp.Radius, a1, a2) left -= math.Abs(a2 - a1) a1 = a2 } }
// Approximate a circular arc of fewer than π/2 // radians with cubic Bézier curve. func partialArc(p *pdf.Path, x, y, r vg.Length, a1, a2 float64) { a := (a2 - a1) / 2 x4 := r * vg.Length(math.Cos(a)) y4 := r * vg.Length(math.Sin(a)) x1 := x4 y1 := -y4 const k = 0.5522847498 // some magic constant f := k * vg.Length(math.Tan(a)) x2 := x1 + f*y4 y2 := y1 + f*x4 x3 := x2 y3 := -y2 // Rotate and translate points into position. ar := a + a1 sinar := vg.Length(math.Sin(ar)) cosar := vg.Length(math.Cos(ar)) x2r := x2*cosar - y2*sinar + x y2r := x2*sinar + y2*cosar + y x3r := x3*cosar - y3*sinar + x y3r := x3*sinar + y3*cosar + y x4 = r*vg.Length(math.Cos(a2)) + x y4 = r*vg.Length(math.Sin(a2)) + y p.Curve(pdfPoint(x2r, y2r), pdfPoint(x3r, y3r), pdfPoint(x4, y4)) }
func traceCurve(a, b, c, d pdf.Point, canvas *pdf.Canvas) { path := new(pdf.Path) path.Move(a) path.Curve(b, c, d) canvas.Stroke(path) }
func Grid(canvas *pdf.Canvas, x, y, w, h, step float64) { canvas.Push() canvas.SetColor(0.75, 0.75, 0.75) canvas.Translate(unit(x), unit(y)) rowCount := int(math.Floor(h / step)) for row := 0; row < rowCount; row++ { bottom := float64(row) * step top := bottom + step start := 0.0 if row%2 == 0 { start += step } for left := start; left < w; left += (2 * step) { right := left + step bottomLeft := point(left, bottom) topRight := point(right, top) path := new(pdf.Path) path.Rectangle(pdf.Rectangle{bottomLeft, topRight}) canvas.Fill(path) } } canvas.Pop() }
func main() { doc := pdf.New() canvas := doc.NewPage(pdf.USLetterWidth, pdf.USLetterHeight) canvas.Translate(500, 500) // canvas.SetColor(230, 100, 30) canvas.SetStrokeColor(20, 40, 60) path := new(pdf.Path) path.Move(pdf.Point{0, 0}) path.Line(pdf.Point{0, 50}) canvas.Stroke(path) text := new(pdf.Text) text.SetFont(pdf.Helvetica, 14) text.Text("Hello, World!") canvas.DrawText(text) canvas.Close() err := doc.Encode(os.Stdout) if err != nil { fmt.Fprintln(os.Stderr, err) os.Exit(1) } }
func EngraveStaff(origin pdf.Point, width, height, lineWidth pdf.Unit, canvas *pdf.Canvas) { path := new(pdf.Path) noteHeight := pdf.Unit(height / 4) for i := 0; i < 5; i++ { path.Move(origin) path.Line(pdf.Point{origin.X + width, origin.Y}) origin.Y = origin.Y + noteHeight } canvas.Push() canvas.SetLineWidth(lineWidth) canvas.Stroke(path) canvas.Pop() }
func main() { doc := pdf.New() canvas := doc.NewPage(pdf.A4Width, pdf.A4Height) path := new(pdf.Path) bottomLeft := pdf.Point{borderWidth, borderWidth} topRight := pdf.Point{pdf.A4Width - borderWidth, pdf.A4Height - borderWidth} path.Rectangle(pdf.Rectangle{bottomLeft, topRight}) canvas.Stroke(path) staffOrigin := pdf.Point{bottomLeft.X + pdf.Unit(10), bottomLeft.Y + pdf.Unit(500)} largeStaff := engraving.NewStaffSpec(engraving.RastralZero) engraving.EngraveStaff(staffOrigin, 12*pdf.Cm, largeStaff.Height(), 0.1*pdf.Pt, canvas) engraving.EngraveSurrogateNoteHead(staffOrigin, largeStaff.StaffSpace(), canvas) nextNote := pdf.Point{} nextNote.X = pdf.Unit(staffOrigin.X + largeStaff.StaffSpace()) nextNote.Y = pdf.Unit(staffOrigin.Y + largeStaff.IndexOffset(0)) engraving.EngraveSurrogateNoteHead(nextNote, largeStaff.StaffSpace(), canvas) nextNote.X = pdf.Unit(staffOrigin.X + (2 * largeStaff.StaffSpace())) nextNote.Y = pdf.Unit(staffOrigin.Y + largeStaff.IndexOffset(7)) engraving.EngraveSurrogateNoteHead(nextNote, largeStaff.StaffSpace(), canvas) nextNote.X = pdf.Unit(staffOrigin.X + (3 * largeStaff.StaffSpace())) nextNote.Y = pdf.Unit(staffOrigin.Y + largeStaff.IndexOffset(-1)) engraving.EngraveSurrogateNoteHead(nextNote, largeStaff.StaffSpace(), canvas) nextNote.X = pdf.Unit(staffOrigin.X + (4 * largeStaff.StaffSpace())) nextNote.Y = pdf.Unit(staffOrigin.Y + largeStaff.IndexOffset(2)) engraving.EngraveSurrogateNoteHead(nextNote, largeStaff.StaffSpace(), canvas) smallStaff := engraving.NewStaffSpec(engraving.RastralEight) staffOrigin.Y = staffOrigin.Y + 5*pdf.Cm engraving.EngraveStaff(staffOrigin, 12*pdf.Cm, smallStaff.Height(), 0.1*pdf.Pt, canvas) canvas.Close() err := doc.Encode(os.Stdout) if err != nil { fmt.Fprintln(os.Stderr, err) os.Exit(1) } }
// Approximate a circular arc using multiple // cubic Bézier curves, one for each π/2 segment. // // This is from: // http://hansmuller-flex.blogspot.com/2011/04/approximating-circular-arc-with-cubic.html func arc(p *pdf.Path, comp vg.PathComp) { x0 := comp.X + comp.Radius*vg.Length(math.Cos(comp.Start)) y0 := comp.Y + comp.Radius*vg.Length(math.Sin(comp.Start)) p.Line(pdfPoint(x0, y0)) a1 := comp.Start end := a1 + comp.Angle sign := 1.0 if end < a1 { sign = -1.0 } left := math.Abs(comp.Angle) for left > 0 { a2 := a1 + sign*math.Min(math.Pi/2, left) partialArc(p, comp.X, comp.Y, comp.Radius, a1, a2) left -= math.Abs(a2 - a1) a1 = a2 } }
// pdfPath returns a pdf.Path from a vg.Path. func pdfPath(c *Canvas, path vg.Path) *pdf.Path { p := new(pdf.Path) for _, comp := range path { switch comp.Type { case vg.MoveComp: p.Move(pdfPoint(comp.X, comp.Y)) case vg.LineComp: p.Line(pdfPoint(comp.X, comp.Y)) case vg.ArcComp: arc(p, comp) case vg.CloseComp: p.Close() default: panic(fmt.Sprintf("Unknown path component type: %d\n", comp.Type)) } } return p }
func main() { doc := pdf.New() canvas := doc.NewPage(pdf.A4Width, pdf.A4Height) path := new(pdf.Path) bottomLeft := pdf.Point{borderWidth, borderWidth} topRight := pdf.Point{pdf.A4Width - borderWidth, pdf.A4Height - borderWidth} path.Rectangle(pdf.Rectangle{bottomLeft, topRight}) canvas.Stroke(path) left := 5 * pdf.Cm right := 15 * pdf.Cm top := 15 * pdf.Cm bottom := 10 * pdf.Cm curve := new(pdf.Path) a := pdf.Point{left, bottom} b := pdf.Point{left, top} c := pdf.Point{right, top} d := pdf.Point{right, bottom} curve.Move(a) curve.Curve(b, c, d) beneath := 5 * pdf.Cm e := pdf.Point{left, beneath} f := pdf.Point{right, beneath} curve.Curve(f, e, a) left = 6.5 * pdf.Cm right = 13.5 * pdf.Cm top = 13.5 * pdf.Cm bottom = 10 * pdf.Cm beneath = 6.5 * pdf.Cm a = pdf.Point{left, 9 * pdf.Cm} b = pdf.Point{left, top} c = pdf.Point{right, top} d = pdf.Point{right, 11 * pdf.Cm} curve.Move(d) curve.Curve(c, b, a) e = pdf.Point{left, beneath} f = pdf.Point{right, beneath} curve.Curve(e, f, d) canvas.FillStroke(curve) canvas.Close() file, err := os.Create("curves.pdf") if err != nil { log.Fatal(err) } err = doc.Encode(file) if err != nil { log.Fatal(err) os.Exit(1) } file.Close() }
func EngraveSurrogateNoteHead(origin pdf.Point, size pdf.Unit, canvas *pdf.Canvas) { outline := new(pdf.Path) topRight := pdf.Point{origin.X + size, origin.Y + size} outline.Rectangle(pdf.Rectangle{origin, topRight}) mid := pdf.Point{origin.X + pdf.Unit(size/2), origin.Y + pdf.Unit(size/2)} midPoints := new(pdf.Path) midPoints.Move(pdf.Point{mid.X, origin.Y}) midPoints.Line(pdf.Point{mid.X, origin.Y + size}) midPoints.Move(pdf.Point{origin.X, mid.Y}) midPoints.Line(pdf.Point{origin.X + size, mid.Y}) canvas.Push() canvas.SetColor(0.6, 0.6, 0.6) canvas.Fill(outline) canvas.SetLineWidth(pdf.Unit(0.1)) canvas.Stroke(midPoints) canvas.Pop() }