package gg import ( "math" "github.com/golang/freetype/raster" "golang.org/x/image/math/fixed" ) func flattenPath(p raster.Path) [][]Point { var result [][]Point var path []Point var cx, cy float64 for i := 0; i < len(p); { switch p[i] { case 0: if len(path) > 0 { result = append(result, path) path = nil } x := unfix(p[i+1]) y := unfix(p[i+2]) path = append(path, Point{x, y}) cx, cy = x, y i += 4 case 1: x := unfix(p[i+1]) y := unfix(p[i+2]) path = append(path, Point{x, y}) cx, cy = x, y i += 4 case 2: x1 := unfix(p[i+1]) y1 := unfix(p[i+2]) x2 := unfix(p[i+3]) y2 := unfix(p[i+4]) points := QuadraticBezier(cx, cy, x1, y1, x2, y2) path = append(path, points...) cx, cy = x2, y2 i += 6 case 3: x1 := unfix(p[i+1]) y1 := unfix(p[i+2]) x2 := unfix(p[i+3]) y2 := unfix(p[i+4]) x3 := unfix(p[i+5]) y3 := unfix(p[i+6]) points := CubicBezier(cx, cy, x1, y1, x2, y2, x3, y3) path = append(path, points...) cx, cy = x3, y3 i += 8 default: panic("bad path") } } if len(path) > 0 { result = append(result, path) } return result } func dashPath(paths [][]Point, dashes []float64, offset float64) [][]Point { var result [][]Point if len(dashes) == 0 { return paths } if len(dashes) == 1 { dashes = append(dashes, dashes[0]) } for _, path := range paths { if len(path) < 2 { continue } previous := path[0] pathIndex := 1 dashIndex := 0 segmentLength := 0.0 // offset if offset != 0 { var totalLength float64 for _, dashLength := range dashes { totalLength += dashLength } offset = math.Mod(offset, totalLength) if offset < 0 { offset += totalLength } for i, dashLength := range dashes { offset -= dashLength if offset < 0 { dashIndex = i segmentLength = dashLength + offset break } } } var segment []Point segment = append(segment, previous) for pathIndex < len(path) { dashLength := dashes[dashIndex] point := path[pathIndex] d := previous.Distance(point) maxd := dashLength - segmentLength if d > maxd { t := maxd / d p := previous.Interpolate(point, t) segment = append(segment, p) if dashIndex%2 == 0 && len(segment) > 1 { result = append(result, segment) } segment = nil segment = append(segment, p) segmentLength = 0 previous = p dashIndex = (dashIndex + 1) % len(dashes) } else { segment = append(segment, point) previous = point segmentLength += d pathIndex++ } } if dashIndex%2 == 0 && len(segment) > 1 { result = append(result, segment) } } return result } func rasterPath(paths [][]Point) raster.Path { var result raster.Path for _, path := range paths { var previous fixed.Point26_6 for i, point := range path { f := point.Fixed() if i == 0 { result.Start(f) } else { dx := f.X - previous.X dy := f.Y - previous.Y if dx < 0 { dx = -dx } if dy < 0 { dy = -dy } if dx+dy > 8 { // TODO: this is a hack for cases where two points are // too close - causes rendering issues with joins / caps result.Add1(f) } } previous = f } } return result } func dashed(path raster.Path, dashes []float64, offset float64) raster.Path { return rasterPath(dashPath(flattenPath(path), dashes, offset)) }