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

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.

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