如何用png-brush和UIBezierPath擦除UIImageView片段 [英] How to erase piece of UIImageView with png-brush and UIBezierPath

问题描述

我有两个UIImageView，第一个超过第二个。我想用画笔擦掉第一张图片的一部分（画笔是带有柔和边缘的png图片），以使第二张图片的一部分可见。

我这样做了方式：

1） touchesMoved 和 [self setNeedsDisplayInRect：[self brushRectForPoint：touch_location]];

2）在（void）drawRect：（CGRect）rect 我调用 [_ brush drawAtPoint：touch_location blendMode：kCGBlendModeDestinationOut alpha：1];

它运作正常，但 touchesMoved 的频率不够，如果用户移动手指太快，我会得到很多短线（或甚至点）而不是一条长线。

我找到了UIBezierPath和将会很有趣。

希望有所帮助！

I have two UIImageView, first above second. I want to erase piece of the first image with brush (brush is a png picture with soft edge) to make piece of the second image visible.

I did that by this way:

1) touchesMoved and [self setNeedsDisplayInRect:[self brushRectForPoint:touch_location]];

2) at (void)drawRect:(CGRect)rect I call [_brush drawAtPoint:touch_location blendMode:kCGBlendModeDestinationOut alpha:1];

It works ok, but frequency of touchesMoved not enough, if user moves finger too fast then I get a lot of short lines (or even points) instead of one long line.

I found information of UIBezierPath and example but author just draws lines by path:

CGContextRef context = UIGraphicsGetCurrentContext();

CGContextAddPath(context, path);

CGContextSetLineCap(context, kCGLineCapRound);
CGContextSetLineWidth(context, self.lineWidth);
CGContextSetStrokeColorWithColor(context, self.lineColor.CGColor);

CGContextStrokePath(context);

How I can draw my png brush with UIBezierPath?

I need something like this

Thanks a lot!

解决方案

There is an open source project which will be useful for you .. iOS-Scratch-n-See. Class ImageMaskView will be interesting to study.

Hope that helps!

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