UIImagePNGRepresentation(UIImage())返回nil [英] UIImagePNGRepresentation(UIImage()) returns nil

问题描述

为什么UIImagePNGRepresentation(UIImage())返回nil?

我试图在测试代码中创建UIImage()只是为了断言它已正确传递.

I'm trying to create a UIImage() in my test code just to assert that it was correctly passed around.

我对两个UIImage的比较方法使用了UIImagePNGRepresentation()，但是由于某种原因，它返回了nil.

My comparison method for two UIImage's uses the UIImagePNGRepresentation(), but for some reason, it is returning nil.

谢谢.

推荐答案

UIKit文档:

返回值

包含PNG数据的数据对象；如果生成数据有问题，则为nil. 如果图像没有数据或基础CGImageRef包含不受支持的位图格式的数据，则此函数可能返回nil.

Return Value

A data object containing the PNG data, or nil if there was a problem generating the data. This function may return nil if the image has no data or if the underlying CGImageRef contains data in an unsupported bitmap format.

初始化 UIImage UIImage()即可创建一个没有数据的UIImage.尽管图像不是nil，但它仍然没有数据.而且，由于图像没有数据，因此UIImagePNGRepresentation()仅返回nil.

When you initialize a UIImage by simply using UIImage(), it creates a UIImage with no data. Although the image isn't nil, it still has no data. And, because the image has no data, UIImagePNGRepresentation() just returns nil.

要解决此问题，您必须对数据使用UIImage.例如:

To fix this, you would have to use UIImage with data. For example:

var imageName: String = "MyImageName.png"
var image = UIImage(named: imageName)
var rep = UIImagePNGRepresentation(image)

imageName是图像的名称，包含在应用程序中.

Where imageName is the name of your image, included in your application.

要使用UIImagePNGRepresentation(image)，image不得为nil，并且还必须具有数据.

In order to use UIImagePNGRepresentation(image), image must not be nil, and it must also have data.

如果要检查它们是否有任何数据，可以使用:

If you want to check if they have any data, you could use:

if(image == nil || image == UIImage()){
  //image is nil, or has no data
}
else{
  //image has data
}

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