package draw2dgl import ( "github.com/golang/freetype/truetype" "github.com/llgcode/draw2d" "golang.org/x/image/math/fixed" ) // DrawContour draws the given closed contour at the given sub-pixel offset. func DrawContour(path draw2d.PathBuilder, ps []truetype.Point, dx, dy float64) { if len(ps) == 0 { return } startX, startY := pointToF64Point(ps[0]) path.MoveTo(startX+dx, startY+dy) q0X, q0Y, on0 := startX, startY, true for _, p := range ps[1:] { qX, qY := pointToF64Point(p) on := p.Flags&0x01 != 0 if on { if on0 { path.LineTo(qX+dx, qY+dy) } else { path.QuadCurveTo(q0X+dx, q0Y+dy, qX+dx, qY+dy) } } else { if on0 { // No-op. } else { midX := (q0X + qX) / 2 midY := (q0Y + qY) / 2 path.QuadCurveTo(q0X+dx, q0Y+dy, midX+dx, midY+dy) } } q0X, q0Y, on0 = qX, qY, on } // Close the curve. if on0 { path.LineTo(startX+dx, startY+dy) } else { path.QuadCurveTo(q0X+dx, q0Y+dy, startX+dx, startY+dy) } } func pointToF64Point(p truetype.Point) (x, y float64) { return fUnitsToFloat64(p.X), -fUnitsToFloat64(p.Y) } func fUnitsToFloat64(x fixed.Int26_6) float64 { scaled := x << 2 return float64(scaled/256) + float64(scaled%256)/256.0 } // FontExtents contains font metric information. type FontExtents struct { // Ascent is the distance that the text // extends above the baseline. Ascent float64 // Descent is the distance that the text // extends below the baseline. The descent // is given as a negative value. Descent float64 // Height is the distance from the lowest // descending point to the highest ascending // point. Height float64 } // Extents returns the FontExtents for a font. // TODO needs to read this https://developer.apple.com/fonts/TrueType-Reference-Manual/RM02/Chap2.html#intro func Extents(font *truetype.Font, size float64) FontExtents { bounds := font.Bounds(fixed.Int26_6(font.FUnitsPerEm())) scale := size / float64(font.FUnitsPerEm()) return FontExtents{ Ascent: float64(bounds.Max.Y) * scale, Descent: float64(bounds.Min.Y) * scale, Height: float64(bounds.Max.Y-bounds.Min.Y) * scale, } }