Question

我正在处理需求，我需要在UIImageView上绘制线条以及触摸点。我需要在按钮点击时清除UIImageView中的所有图纸。我能够绘制线条，但无法在按钮点击时清除线条。我甚至想要实现清除所有和撤消选项。有人请指导我的方式，我可以实现清除所有和撤消选项。下面是我用来实现绘图的代码。不确定如何实现全部清除和撤消绘图。

    UITouch *touch = [touches anyObject];

CGPoint currentPoint = [touch locationInView:_selectedImageView];

 _ctx = UIGraphicsGetCurrentContext();

CGContextSaveGState(_ctx);

UIGraphicsBeginImageContext(self.view.frame.size);
[self.selectedImageView.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brush );
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, 1.0);
CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeNormal);

CGContextStrokePath(UIGraphicsGetCurrentContext());
self.selectedImageView.image = UIGraphicsGetImageFromCurrentImageContext();
[self.selectedImageView setAlpha:opacity];
UIGraphicsEndImageContext();

lastPoint = currentPoint;

Answer 1

我能够得到我的问题的解决方案，以清除从下面的示例中绘制的点或线。通过从github下面的示例，我能够实现clear all和undo。 https://github.com/backslash112/paint-with-undo/tree/master

如何清除使用触摸点绘制的uiview上绘制的线条

1 个答案: