Turning an NSImage* into a CGImageRef?

I开发者_运维百科s there an easy way to do this that works in 10.5?

In 10.6 I can use nsImage CGImageForProposedRect: NULL context: NULL hints: NULL

If I'm not using 1b black and white images (Like Group 4 TIFF), I can use bitmaps, but cgbitmaps seem to not like that setup... Is there a general way of doing this?

I need to do this because I have an IKImageView that seems to only want to add CGImages, but all I've got are NSImages. Currently, I'm using a private setImage:(NSImage*) method that I'd REALLY REALLY rather not be using...

Found the following solution on this page:

NSImage* someImage;
// create the image somehow, load from file, draw into it...
CGImageSourceRef source;

source = CGImageSourceCreateWithData((CFDataRef)[someImage TIFFRepresentation], NULL);
CGImageRef maskRef =  CGImageSourceCreateImageAtIndex(source, 0, NULL);

All the methods seem to be 10.4+ so you should be fine.

[This is the long way around. You should only do this if you're still supporting an old version of OS X. If you can require 10.6 or later, just use the CGImage method instead.]

1. Create a CGBitmapContext.
2. Create an NSGraphicsContext for the bitmap context.
3. Set the graphics context as the current context.
4. Draw the image.
5. Create the CGImage from the contents of the bitmap context.
6. Release the bitmap context.

As of Snow Leopard, you can just ask the image to create a CGImage for you, by sending the NSImage a CGImageForProposedRect:context:hints: message.

Here's a more detailed answer for using - CGImageForProposedRect:context:hints::

NSImage *image = [NSImage imageNamed:@"image.jpg"];

NSRect imageRect = NSMakeRect(0, 0, image.size.width, image.size.height);

CGImageRef cgImage = [image CGImageForProposedRect:&imageRect context:NULL hints:nil];

Just did this using CGImageForProposedRect:context:hints:...

NSImage *image; // an image
NSGraphicsContext *context = [NSGraphicsContext currentContext];
CGRect imageCGRect = CGRectMake(0, 0, image.size.width, image.size.height);
NSRect imageRect = NSRectFromCGRect(imageCGRect);
CGImageRef imageRef = [image CGImageForProposedRect:&imageRect context:context hints:nil];

As of 2021, CALayers contents can directly be feed with NSImage but you still may get an
[Utility] unsupported surface format: LA08 warning. After a couple of days research and testing around i found out that this Warning is triggered if you created an NSView with backingLayer, aka CALayer and just used an NSImage to feed its contents. This alone is not much of a problem. But if you try to render it via [self.layer renderInContext:ctx], each rendering will trigger the warning again.

To make use simple, i created an NSImage extension to fix this..

@interface NSImage (LA08FIXExtension)
-(id)CGImageRefID;
@end

@implementation NSImage (LA08FIXExtension)

-(id)CGImageRefID {
    NSSize size = [self size];
    NSRect rect = NSMakeRect(0, 0, size.width, size.height);
    CGImageRef ref = [self CGImageForProposedRect:&rect context:[NSGraphicsContext currentContext] hints:NULL];
    return (__bridge id)ref;
}

@end

see how it does not return an CGImageRef directly but a bridged cast to id..! This does the trick.

Now you can use it like..

CALayer *somelayer = [CALayer layer];
somelayer.frame = ... 
somelayer.contents = [NSImage imageWithName:@"SomeImage"].CGImageRefID;

PS: posted her because if you got that problem also, google will lead you to this Thread of answers anyway, and all above answers inspired me for this fix.