iphone - Could anyone tell me why UIImage.ciimage is null

Question

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?

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

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ADD

for example, the code like below return null:

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

but if in this way CIImage is not null:

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

Answer 1

这是因为这个 UIImage 实际上不是 CIImage。换句话说，CIImage只有当 UIImage 已经由 CIImage 支持时（例如，因为它是由 生成的imageWithCIImage:），UIImage 才不是 nil。您不能使用它来神奇地将 UIImage 转换为 CIImage，就像您似乎希望做的那样。

文档实际上对此非常清楚。永远值得一读。