我正在研究绘图路径,并且发现至少在某些情况下,UIBezierPath的性能优于我认为相当于Core Graphics的性能。-drawRect:
下面的方法创建两条路径:一条UIBezierPath和一条CGPath。路径除了位置外都是相同的,但是抚摸CGPath的时间大约是抚摸UIBezierPath的两倍。
- (void)drawRect:(CGRect)rect
{
CGContextRef ctx = UIGraphicsGetCurrentContext();
// Create the two paths, cgpath and uipath.
CGMutablePathRef cgpath = CGPathCreateMutable();
CGPathMoveToPoint(cgpath, NULL, 0, 100);
UIBezierPath *uipath = [[UIBezierPath alloc] init];
[uipath moveToPoint:CGPointMake(0, 200)];
// Add 200 curve segments to each path.
int iterations = 200;
CGFloat cgBaseline = 100;
CGFloat uiBaseline = 200;
CGFloat xincrement = self.bounds.size.width / iterations;
for (CGFloat x1 = 0, x2 = xincrement;
x2 < self.bounds.size.width;
x1 = x2, x2 += xincrement)
{
CGPathAddCurveToPoint(cgpath, NULL, x1, cgBaseline-50, x2, cgBaseline+50, x2, cgBaseline);
[uipath addCurveToPoint:CGPointMake(x2, uiBaseline)
controlPoint1:CGPointMake(x1, uiBaseline-50)
controlPoint2:CGPointMake(x2, uiBaseline+50)];
}
[[UIColor blackColor] setStroke];
CGContextAddPath(ctx, cgpath);
// Stroke each path.
[self strokeContext:ctx];
[self strokeUIBezierPath:uipath];
[uipath release];
CGPathRelease(cgpath);
}
- (void)strokeContext:(CGContextRef)context
{
CGContextStrokePath(context);
}
- (void)strokeUIBezierPath:(UIBezierPath*)path
{
[path stroke];
}
这两个路径都使用CGContextStrokePath(),因此我创建了单独的方法来描画每个路径,以便可以在Instruments中查看每个路径所用的时间。以下是典型结果(调用树倒置);您可以看到这-strokeContext:
需要9.5秒,而-strokeUIBezierPath:
仅需5秒:
Running (Self) Symbol Name
14638.0ms 88.2% CGContextStrokePath
9587.0ms 57.8% -[QuartzTestView strokeContext:]
5051.0ms 30.4% -[UIBezierPath stroke]
5051.0ms 30.4% -[QuartzTestView strokeUIBezierPath:]
看来UIBezierPath在某种程度上优化了它创建的路径,或者我以一种幼稚的方式创建了CGPath。如何加快CGPath绘制速度?