来源：http://blog.sina.com.cn/s/blog_796ffec50100y5ac.html
UIView *view = [[UIView alloc]initWithFrame:CGRectMake(50, 50, 100, 100)];
CATiledLayer *tiled=(CATiledLayer *)[view layer];
tiled.borderColor = [UIColor whiteColor].CGColor;
tiled.borderWidth = 3.0;
tiled.shouldRasterize=YES;
此方法只是将Layer的borderColor的颜色和UIView所在的试图的颜色设置成相同的颜色，这样因为颜色相同的原因所以看不出来
解决：
//旋转
CGAffineTransform transform = CGAffineTransformIdentity;
transform = CGAffineTransformRotate(transform, radians(degre));
//无锯齿 Default YES
CGContextSetAllowsAntialiasing(context, YES);