如何知道如果在XCode（swift或Objective C）中触及.png的唯一可见区域 [英] How to know that if the only visible area of a .png is touched in XCode (swift or objective C)

问题描述

我已经在Xcode中将.png图像导入 UIImageView ，我想要做的是触摸图像时，它将被隐藏。

但我的问题是png图像包含透明部分，当我触摸透明部分时，操作继续进行。我希望只有在触摸图像的可见部分时才会继续操作。请告诉我如何解决问题。

解决方案

我创建了一个自定义UIButton子类，其行为完全如您所描述的那样，看看：
$ g $

它是用Swift编写的，但它很容易转换为Objective-c。

方法是从触摸点获取像素数据并访问RGBA值，在这种情况下，我们读取A（alpha）并检查它是否高于我们的阈值。

查看一些代码：

  func alphaFromPoint（point：CGPoint） - > CGFloat {
 var pixel：[UInt8] = [0,0,0,0] 
 let colorSpace = CGColorSpaceCreateDeviceRGB（）; 
 let alphaInfo = CGBitmapInfo（CGImageAlphaInfo.PremultipliedLast.rawValue）
 let context = CGBitmapContextCreate（& pixel，1,1,8,4，colorSpace，alphaInfo）
 
 CGContextTranslateCTM（ context，-point.x，-point.y）; 
 
 self.layer.renderInContext（context）
 
 let floatAlpha = CGFloat（pixel [3]）
 return floatAlpha 
} 
  

您可以采用 floatAlpha 值并将其与可接受的值进行比较alpha的值：

 覆盖func pointInside（点：CGPoint，withEvent事件：UIEvent？） - > Bool {
返回self.alphaFromPoint（点）> = 100 
} 
  

I have imported a .png image into UIImageView in Xcode and what I want to make is when the image is touched, it will be hidden.

But my problem is that the png image contains transparent parts and when I touch on the transparent parts, the action goes on. I want the action to go on only when the visible part of the image is touched. Please tell me how to solve the problem.

解决方案

I have created a custom UIButton subclass that behaves exactly as you describe, have a look: https://github.com/spagosx/iOS-Shaped-Button-Swift

It's written in Swift, but it's easily convertible to Objective-c.

The approach is to get the pixel data from the touch point and to access the RGBA values, in this case we read A (alpha) and check if it is higher than our threshold.

Looking at a bit of code:

func alphaFromPoint(point: CGPoint) -> CGFloat {
       var pixel: [UInt8] = [0, 0, 0, 0]
       let colorSpace = CGColorSpaceCreateDeviceRGB();
       let alphaInfo = CGBitmapInfo(CGImageAlphaInfo.PremultipliedLast.rawValue)
       let context = CGBitmapContextCreate(&pixel, 1, 1, 8, 4, colorSpace, alphaInfo)

       CGContextTranslateCTM(context, -point.x, -point.y);

       self.layer.renderInContext(context)

       let floatAlpha = CGFloat(pixel[3])
       return floatAlpha
}

You can than take the floatAlpha value and compare it with your acceptable value of alpha:

    override func pointInside(point: CGPoint, withEvent event: UIEvent?) -> Bool {
        return self.alphaFromPoint(point) >= 100
    }

这篇关于如何知道如果在XCode（swift或Objective C）中触及.png的唯一可见区域的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！