iphone - 删除 quartz 2d 中上下文中的剪辑

Question

我用弧线绘制了一条通往上下文的路径，将其设置为剪辑，并将图像绘制到该剪辑中。

CGContextBeginPath(context);
CGContextMoveToPoint(context, lineStartPoint.x, lineStartPoint.y);
CGContextAddArc(context, lineStartPoint.x, lineStartPoint.y, 105, toAngle*M_PI,fromAngle*M_PI , 1);
CGContextMoveToPoint(context, toLinePoint.x, toLinePoint.y);
CGContextClip(context);
[[UIImage imageNamed:@"gradientfill.png"] drawInRect:[self bounds]];

效果非常好，如图所示

我的问题是，在渐变的底部我画了一个圆圈，我希望它存在于剪辑之外，它应该看起来像这样

如何让我的上下文停止剪辑，以便我可以将该圆圈置于剪辑之外？

我画圆的代码是

CGMutablePathRef path = CGPathCreateMutable();
CGRect toHandleRect = CGRectMake(toLinePoint.x-5, toLinePoint.y-5, 10, 10);    
CGPathAddEllipseInRect(path, NULL, toHandleRect);
CGContextAddPath(context, path);
CGPathRelease(path);

我希望用户能够将小圆圈拖动到该 View 中的任何位置。

Answer 1

您可以发出 CGContextSaveGState + CGContextRestoreGState 对，如下例所示:

// Saves the context including the current clipping region.
CGContextSaveGState(context);

// Build you clip region and do some drawing
CGContextBeginPath(context);
CGContextMoveToPoint(context, lineStartPoint.x, lineStartPoint.y);
CGContextAddArc(context, lineStartPoint.x, lineStartPoint.y, 105, toAngle*M_PI,fromAngle*M_PI , 1);
CGContextMoveToPoint(context, toLinePoint.x, toLinePoint.y);
CGContextClip(context);

[[UIImage imageNamed:@"gradientfill.png"] drawInRect:[self bounds]];

CGMutablePathRef path = CGPathCreateMutable();
CGRect toHandleRect = CGRectMake(toLinePoint.x-5, toLinePoint.y-5, 10, 10);    
CGPathAddEllipseInRect(path, NULL, toHandleRect);
CGContextAddPath(context, path);
CGPathRelease(path);

// Restore the original state
CGContextRestoreGState(context);