Sharing Memory Between CGImageRef and UIImage

Question

Is there any way to create a UIImage object from an offscreen surface without copying the underlying pixel data?

I would like to do something like this:

// These numbers are made up obviously...
CGContextRef offscreenContext = MyCreateBitmapContext(width, height);

// Draw into the offscreen buffer
// Draw commands not relevant...

// Convert offscreen into CGImage
// This consumes ~15MB
CGImageRef offscreenContextImage = CGBitmapContextCreateImage(offscreenContext);

// This allocates another ~15MB
// Is there any way to share the bits from the 
// CGImageRef instead of copying the data???
UIImage * newImage = [[UIImage alloc] initWithCGImage:offscreenContextImage];

// Releases the original 15MB, but the spike of 30MB total kills the app.
CGImageRelease(offscreenContextImage);
CGContextRelease(offscreenContext);

The memory is released and levels out at the acceptable size, but the 30MB memory spike is what kills the application. Is there any way to share the pixel data?

I've considered saving the offscreen buffer to a file and loading the data again, but this is a hack and the convenience methods for the iPhone require a UIImage to save it...

Answer 1

Maybe

UIImage *newImage = [[UIImage alloc[ initWithData:offScreenContext];

Answer 2

You could try releasing the context right after you created the CGImage, releasing the memory used by the context, because CGBitmapContextCreateImage() creates a copy of the context.

Like this:

CGImageRef offscreenContextImage = CGBitmapContextCreateImage(offscreenContext);

CGContextRelease(offscreenContext);

UIImage * newImage = [[UIImage alloc] initWithCGImage:offscreenContextImage];

// ...

CGImageRelease(offscreenContextImage);