(Swift+iOS)字符串轨迹转贝塞尔曲线，实现动态写字效果

前两天下载了一个Swift的HUD提示效果，偶然发现其中的提示效果上面的文字是动态书写的。感觉挺不错的，代码地址如下：

http://code.cocoachina.com/view/129442。

然后自己使用里面部分技术写了一个OC版的，

Demo地址：https://github.com/longitachi/WritingEffect/tree/master

效果图：

Swift具体实现(仅仅贴出Nsstring转UIBezierPath的方法，动画简单自己加，或者下载源码)：

class func bezierPathFrom(string:String) -> UIBezierPath{
        
        let paths = CGPathCreateMutable()
        let fontName = __CFStringMakeConstantString("SnellRoundhand")
        let fontRef:AnyObject = CTFontCreateWithName(fontName,18,nil)
        
        let attrString = NSAttributedString(string: string,attributes: [kCTFontAttributeName as String : fontRef])
        let line = CTLineCreateWithAttributedString(attrString as CFAttributedString)
        let runA = CTLineGetGlyphRuns(line)
        
        
        for (var runIndex = 0; runIndex < CFArrayGetCount(runA); runIndex++){
            let run = CFArrayGetValueAtIndex(runA,runIndex);
            let runb = unsafeBitCast(run,CTRun.self)
            
            let  CTFontName = unsafeBitCast(kCTFontAttributeName,UnsafePointer<Void>.self)
            
            let runFontC = CFDictionaryGetValue(CTRunGetAttributes(runb),CTFontName)
            let runFontS = unsafeBitCast(runFontC,CTFont.self)
            
            let width = UIScreen.mainScreen().bounds.width
            
            var temp = 0
            var offset:CGFloat = 0.0
            
            for(var i = 0; i < CTRunGetGlyphCount(runb); i++){
                let range = CFRangeMake(i,1)
                let glyph:UnsafeMutablePointer<CGGlyph> = UnsafeMutablePointer<CGGlyph>.alloc(1)
                glyph.initialize(0)
                let position:UnsafeMutablePointer<CGPoint> = UnsafeMutablePointer<CGPoint>.alloc(1)
                position.initialize(CGPointZero)
                CTRunGetGlyphs(runb,range,glyph)
                CTRunGetPositions(runb,position);
                
                let temp3 = CGFloat(position.memory.x)
                let temp2 = (Int) (temp3 / width)
                let temp1 = 0
                if(temp2 > temp1){
                    
                    temp = temp2
                    offset = position.memory.x - (CGFloat(temp) * width)
                }
                let path = CTFontCreatePathForGlyph(runFontS,glyph.memory,nil)
                let x = position.memory.x - (CGFloat(temp) * width) - offset
                let y = position.memory.y - (CGFloat(temp) * 80)
                var transform = CGAffineTransformMakeTranslation(x,y)
                CGPathAddpath(paths,&transform,path)
                glyph.destroy()
                glyph.dealloc(1)
                position.destroy()
                position.dealloc(1)
            }
            
        }
        
        let bezierPath = UIBezierPath()
        bezierPath.movetoPoint(CGPointZero)
        bezierPath.appendpath(UIBezierPath(CGPath: paths))
        
        return bezierPath
    }

根据Swift翻译的OC版本，实现如下：

- (UIBezierPath *)transformToBezierPath:(Nsstring *)string
{
    CGMutablePathRef paths = CGPathCreateMutable();
    CFStringRef fontNameRef = CFSTR("SnellRoundhand");
    CTFontRef fontRef = CTFontCreateWithName(fontNameRef,nil);
    
    NSAttributedString *attrString = [[NSAttributedString alloc] initWithString:string attributes:@{(__bridge Nsstring *)kCTFontAttributeName: (__bridge UIFont *)fontRef}];
    CTLineRef lineRef = CTLineCreateWithAttributedString((CFAttributedStringRef)attrString);
    CFArrayRef runArrRef = CTLineGetGlyphRuns(lineRef);
    
    for (int runIndex = 0; runIndex < CFArrayGetCount(runArrRef); runIndex++) {
        const void *run = CFArrayGetValueAtIndex(runArrRef,runIndex);
        CTRunRef runb = (CTRunRef)run;
        
        const void *CTFontName = kCTFontAttributeName;
        
        const void *runFontC = CFDictionaryGetValue(CTRunGetAttributes(runb),CTFontName);
        CTFontRef runFontS = (CTFontRef)runFontC;
        
        CGFloat width = [UIScreen mainScreen].bounds.size.width;
        
        int temp = 0;
        CGFloat offset = .0;
        
        for (int i = 0; i < CTRunGetGlyphCount(runb); i++) {
            CFRange range = CFRangeMake(i,1);
            CGGlyph glyph = 0;
            CTRunGetGlyphs(runb,&glyph);
            CGPoint position = CGPointZero;
            CTRunGetPositions(runb,&position);
            
            CGFloat temp3 = position.x;
            int temp2 = (int)temp3/width;
            CGFloat temp1 = 0;
            
            if (temp2 > temp1) {
                temp = temp2;
                offset = position.x - (CGFloat)temp;
            }
            
            CGPathRef path = CTFontCreatePathForGlyph(runFontS,glyph,nil);
            CGFloat x = position.x - (CGFloat)temP*width - offset;
            CGFloat y = position.y - (CGFloat)temp * 80;
            CGAffineTransform transform = CGAffineTransformMakeTranslation(x,y);
            CGPathAddpath(paths,path);
            
            CGPathRelease(path);
        }
        CFRelease(runb);
        CFRelease(runFontS);
    }
    
    UIBezierPath *bezierPath = [UIBezierPath bezierPath];
    [bezierPath movetoPoint:CGPointZero];
    [bezierPath appendpath:[UIBezierPath bezierPathWithCGPath:paths]];
    
    CGPathRelease(paths);
    CFRelease(fontNameRef);
    CFRelease(fontRef);
    
    return bezierPath;
}