手寫字

drawText.swift

    var charLayers = [CAShapeLayer]()

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        
        for layer in self.charLayers {
            layer.removeFromSuperlayer()
        }
        
        let stringAttributes = [ NSAttributedString.Key.font: UIFont(name: "Zapfino", size: 32.0)! ]
        let attributedString = NSMutableAttributedString(string: "Hello world!", attributes: stringAttributes )
        let charPaths = self.charactersPath(attributedString: attributedString)
        
        let charSize = charPaths.bounds.size
        
        let point = view.center
        charPaths.apply(CGAffineTransform(translationX: point.x-charSize.width * 0.5, y: point.y*0.5))
        
        let shapeLayer = CAShapeLayer()
        shapeLayer.fillColor = UIColor.clear.cgColor
        shapeLayer.strokeColor = UIColor.red.cgColor
        shapeLayer.lineWidth = 2
        shapeLayer.path = charPaths.cgPath
        
        view.layer.addSublayer(shapeLayer)
        let animation = CABasicAnimation(keyPath: "strokeEnd")
        animation.fromValue = 0
        animation.duration = 2.2
        shapeLayer.add(animation, forKey: "charAnimation")
    }
    
    func charactersPath(attributedString: NSAttributedString) -> UIBezierPath {
        
        let line = CTLineCreateWithAttributedString(attributedString)
        
        guard let glyphRuns = CTLineGetGlyphRuns(line) as? [CTRun] else { return UIBezierPath()}
        
        let characterPaths = CGMutablePath()
        
        for glyphRun in glyphRuns {
            guard let attributes = CTRunGetAttributes(glyphRun) as? [String:AnyObject] else { continue }
            let font = attributes[kCTFontAttributeName as String] as! CTFont
            
            for index in 0..<CTRunGetGlyphCount(glyphRun) {
                let glyphRange = CFRangeMake(index, 1)
                
                var glyph = CGGlyph()
                CTRunGetGlyphs(glyphRun, glyphRange, &glyph)
                
                var characterPosition = CGPoint()
                CTRunGetPositions(glyphRun, glyphRange, &characterPosition)
                
                if let glyphPath = CTFontCreatePathForGlyph(font, glyph, nil) {
                    let transform = CGAffineTransform(a: 1, b: 0, c: 0, d: -1, tx: characterPosition.x, ty: characterPosition.y)
                    characterPaths.addPath(glyphPath, transform: transform)
                }
            }
        }
        
        return UIBezierPath(cgPath: characterPaths)
    }