问题
I've been making a simple painting app for the iphone. I'm trying to convert the drawn image to a transparent PNG (I don't want a white background). I'd also like to get a UIImage representation to use in a UIImageView.
Currently, I respond to touch events and draw paths to a CGLayer which is then drawn to my views context. I have access to both the CGLayer as well as the view itself. Currently, I output my view to an image using:
UIGraphicsBeginImageContext(drawingView.bounds.size);
[drawingView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
This only uses the view to create a UIImage.
Since the view has a white background it is inluded in the UIImage I create. I'd like to get a UIImage that does not have this white background so I can display and write to a PNG file.
I think I should use the CGLayer I have directly but I'm not sure how to get that from the CGLayerRef type I have access to.
Any ideas would be much appreciated.
- Aleem
回答1:
I just dealt with this. Don't draw a background on the CGLayer and then set the background of the UIView to:
self.backgroundColor = [UIColor clearColor];
That should do it and your png will have a transparent background.
来源：https://stackoverflow.com/questions/1101254/converting-a-cglayer-to-a-transparent-uiimage-and-png-file-in-coregraphics-iph