iOS按文字路径绘画
转自：http://blog.csdn.net/xoxo_x/article/details/71512943

#import "ViewController.h"
#import <CoreText/CoreText.h>

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    UIBezierPath *path = [self getStringLayer:@"Chris Martin"];
    
    CAShapeLayer *pathLayer = [CAShapeLayer layer];
    pathLayer.frame = self.view.layer.bounds;
    pathLayer.bounds = CGPathGetBoundingBox(path.CGPath);
    pathLayer.backgroundColor = [[UIColor yellowColor] CGColor];
    pathLayer.geometryFlipped = YES;
    pathLayer.path = path.CGPath;
    pathLayer.strokeColor = [UIColor redColor].CGColor;
    pathLayer.fillColor = [UIColor clearColor].CGColor;
    pathLayer.lineWidth = 1.0f;
    pathLayer.lineJoin = kCALineJoinMiter;
    [self.view.layer addSublayer:pathLayer];
    
    UIImage *penImage = [UIImage imageNamed:@"snowflower"];
    CALayer *penLayer = [CALayer layer];
    penLayer.contents = (id)penImage.CGImage;
    penLayer.anchorPoint = CGPointZero;
    penLayer.frame = CGRectMake(0.0f, 0.0f, penImage.size.width, penImage.size.height);
    [pathLayer addSublayer:penLayer];

    CABasicAnimation *pathAnimation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
    pathAnimation.duration = 10.0;
    pathAnimation.fromValue = [NSNumber numberWithFloat:0.0f];
    pathAnimation.toValue = [NSNumber numberWithFloat:1.0f];
    [pathLayer addAnimation:pathAnimation forKey:@"strokeStart"];
    pathAnimation.speed = 0.1;
    pathAnimation.timeOffset = 0;

    CAKeyframeAnimation *penAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
    penAnimation.duration = 10.0;
    penAnimation.path = pathLayer.path;
    penAnimation.calculationMode = kCAAnimationPaced;
    //penAnimation.delegate = self;
    [penLayer addAnimation:penAnimation forKey:@"position"];
}


- (UIBezierPath *)getStringLayer:(NSString *)str{
    //创建可变path
    CGMutablePathRef letters = CGPathCreateMutable();
    
    //    HelveticaNeue-UltraLight
    //设置字体
    CTFontRef font = CTFontCreateWithName(CFSTR("Helvetica-Bold"), 32.0f, NULL);
    NSDictionary *attrs = [NSDictionary dictionaryWithObjectsAndKeys:
                           (__bridge id)font, kCTFontAttributeName,
                           nil];
    NSAttributedString *attrString = [[NSAttributedString alloc] initWithString:str
                                                                     attributes:attrs];
    //根据字符串创建 line
    CTLineRef line = CTLineCreateWithAttributedString((CFAttributedStringRef)attrString);
    
    //获取每一个字符作为数组
    CFArrayRef runArray = CTLineGetGlyphRuns(line);
    
    // 遍历字符数组
    for (CFIndex runIndex = 0; runIndex < CFArrayGetCount(runArray); runIndex++)
    {
        // Get FONT for this run
        CTRunRef run = (CTRunRef)CFArrayGetValueAtIndex(runArray, runIndex);
        CTFontRef runFont = CFDictionaryGetValue(CTRunGetAttributes(run), kCTFontAttributeName);
        
        // for each GLYPH in run
        for (CFIndex runGlyphIndex = 0; runGlyphIndex < CTRunGetGlyphCount(run); runGlyphIndex++)
        {
            // get Glyph & Glyph-data
            CFRange thisGlyphRange = CFRangeMake(runGlyphIndex, 1);
            CGGlyph glyph;
            CGPoint position;
            CTRunGetGlyphs(run, thisGlyphRange, &glyph);
            CTRunGetPositions(run, thisGlyphRange, &position);
            
            // Get PATH of outline
            {
                CGPathRef letter = CTFontCreatePathForGlyph(runFont, glyph, NULL);
                CGAffineTransform t = CGAffineTransformMakeTranslation(position.x, position.y);
                CGPathAddPath(letters, &t, letter);
                CGPathRelease(letter);
            }
        }
    }
    CFRelease(line);
    UIBezierPath *path = [UIBezierPath bezierPath];
    [path moveToPoint:CGPointZero];
    [path appendPath:[UIBezierPath bezierPathWithCGPath:letters]];
    CGPathRelease(letters);
    CFRelease(font);
    return path;
}


@end