Turning an NSImage* into a CGImageRef?

问题

Is 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...

回答1:

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.

回答2:

[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.]

Create a CGBitmapContext.
Create an NSGraphicsContext for the bitmap context.
Set the graphics context as the current context.
Draw the image.
Create the CGImage from the contents of the bitmap context.
Release the bitmap context.

回答3:

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.

回答4:

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];

回答5:

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];

来源：https://stackoverflow.com/questions/2548059/turning-an-nsimage-into-a-cgimageref

标签

objective-c

cocoa

core-graphics

nsimage

cgimage