如何从 UIView 的内容中获取 CGImageRef？

Question

I have an UIView where I was drawing some stuff inside -drawRect:. Now I need a CGImageRef from this graphics context or bitmap of the UIView. Is there an easy way to get that?

Answer 1

Like this (typed from memory, so it might not be 100% correct):

// Get a UIImage from the view's contents
UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.opaque, view.contentScaleFactor);
CGContextRef context = UIGraphicsGetCurrentContext();
[view.layer renderInContext:context];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

// Convert UIImage to CGImage
CGImageRef cgImage = image.CGImage;

Answer 2

Swift 5

extension UIView {
    var cgImage: CGImage? {
        guard bounds.size.width > 0 && bounds.size.height > 0 else {return nil}
        UIGraphicsBeginImageContextWithOptions(bounds.size, isOpaque, contentScaleFactor)
        layer.render(in: UIGraphicsGetCurrentContext()!)
        defer {UIGraphicsEndImageContext()}
        return UIGraphicsGetImageFromCurrentImageContext()!.cgImage!
    }
}

Answer 3

Also make sure that you add

#import <QuartzCore/QuartzCore.h>

to your code