谁能告诉我为什么UIImage.ciimage为null [英] Could anyone tell me why UIImage.ciimage is null

问题描述

我发现在IOS中 UIImage 可以改为 CIImage 。在UIImage中有一个属性CIImage。当我使用UIImage时，UIImage对象不为null但 UIImage.ciimage 为空，为什么？

I found that in IOS UIImage can change to CIImage.and there is a property CIImage in UIImage. and when i use the UIImage,UIImage object is not null but UIImage.ciimage is null ,why?

原谅我的愚蠢问题，如果有人可以帮助我，非常感谢你。

forgive my stupid question if someone can help me ,thank you very much.

ADD

例如，下面的代码返回null：

for example, the code like below return null:

UIImage *image = [UIImage imageNamed:@"test.jpg"];
CIImage *ciImage = image.CIImage

但如果以这种方式CIImage不为空：

but if in this way CIImage is not null:

UIImage *image = [UIImage imageNamed:@"test.jpg"];
CIImage *myImage = [[CIImage alloc] initWithCGImage:image.CGImage options:nil];

推荐答案

这是因为这个UIImage实际上不是CIImage 。换句话说，UIImage的 CIImage 只有在UIImage已经由CIImage支持时才会为零（例如，因为它是由 imageWithCIImage生成的：）。您无法使用它来神奇地将UIImage变成CIImage，正如您似乎希望的那样。

It is because this UIImage is not in fact a CIImage. In other words, UIImage's CIImage is not nil only if the UIImage is backed by a CIImage already (e.g. because it was generated by imageWithCIImage:). You can't use this to magically turn the UIImage into a CIImage, as you seem to be hoping to do.

文档实际上非常清楚。总是值得一读。

The documentation is actually pretty clear on this. Always worth a read.

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