iOS实现绘画文字动画

通过Core Text 结合 Bezier 曲线和 CAShapeLayer 可以做出绘画文字的动画。如下代码：

CGMutablePathRef letters = CGPathCreateMutable();   //创建path
    
    CTFontRef font = CTFontCreateWithName(CFSTR("Helvetica-Bold"), 100.0f, NULL);       //设置字体
    
    NSDictionary *attrs = [NSDictionary dictionaryWithObjectsAndKeys:
                           (id)font, kCTFontAttributeName,
                           nil];
    NSAttributedString *attrString = [[NSAttributedString alloc] initWithString:@"" attributes:attrs];
    CTLineRef line = CTLineCreateWithAttributedString((CFAttributedStringRef)attrString);   //创建line
	CFArrayRef runArray = CTLineGetGlyphRuns(line);     //根据line获得一个数组
    
    // 获得每一个 run
    for (CFIndex runIndex = 0; runIndex < CFArrayGetCount(runArray); runIndex++)
    {
        // 获得 run 的字体
        CTRunRef run = (CTRunRef)CFArrayGetValueAtIndex(runArray, runIndex);
        CTFontRef runFont = CFDictionaryGetValue(CTRunGetAttributes(run), kCTFontAttributeName);
        
        // 获得 run 的每一个形象字
        for (CFIndex runGlyphIndex = 0; runGlyphIndex < CTRunGetGlyphCount(run); runGlyphIndex++) 
        {
            // 获得形象字
            CFRange thisGlyphRange = CFRangeMake(runGlyphIndex, 1);
            //获得形象字信息
            CGGlyph glyph;
            CGPoint position;
            CTRunGetGlyphs(run, thisGlyphRange, &glyph);
            CTRunGetPositions(run, thisGlyphRange, &position);
            
            // 获得形象字外线的path
            {
                CGPathRef letter = CTFontCreatePathForGlyph(runFont, glyph, NULL);
                CGAffineTransform t = CGAffineTransformMakeTranslation(position.x, position.y);
                CGPathAddPath(letters, &t, letter);
                CGPathRelease(letter);
            }
        }
    }
    CFRelease(line);
    
    //根据构造出的 path 构造 bezier 对象
    UIBezierPath *path = [UIBezierPath bezierPath];
    [path moveToPoint:CGPointZero];
    [path appendPath:[UIBezierPath bezierPathWithCGPath:letters]];
    
    CGPathRelease(letters);
    CFRelease(font);
    
    //根据 bezier 创建 shapeLayer对象
    CAShapeLayer *pathLayer = [CAShapeLayer layer];
    pathLayer.frame = self.animationLayer.bounds;
	pathLayer.bounds = CGPathGetBoundingBox(path.CGPath);
    pathLayer.geometryFlipped = YES;
    pathLayer.path = path.CGPath;
    pathLayer.strokeColor = [[UIColor blackColor] CGColor];
    pathLayer.fillColor = nil;
    pathLayer.lineWidth = 3.0f;
    pathLayer.lineJoin = kCALineJoinBevel;
    
    [self.animationLayer addSublayer:pathLayer];
    
    self.pathLayer = pathLayer;

//开始动画

- (void) startAnimation
{
    [self.pathLayer removeAllAnimations];

    CABasicAnimation *pathAnimation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
    pathAnimation.duration = 10.0;
    pathAnimation.fromValue = [NSNumber numberWithFloat:0.0f];
    pathAnimation.toValue = [NSNumber numberWithFloat:1.0f];
    [self.pathLayer addAnimation:pathAnimation forKey:@"strokeEnd"];
 }

代码来源： http://oleb.net/blog/2010/12/animating-drawing-of-cgpath-with-cashapelayer/