How to composite several NSImages into one big image?

Question

I have a collection of objects which describe an image-name, its size and it's X/Y location. The collection is sorted by "layers", so I can composite the images in a sort of painter's algorithm.

From this, I can determine the rectangle necessary to hold all of the images, so now what I want to do is:

• Create some sort of buffer to hold the result (The NS equivalent of what iPhoneOS calls UIGraphicsContext.)
• Draw all the images into the buffer.
• Snag a new NSImage out of the composited result of the buffer.

In iPhoneOS, this is the code that does what I want:

UIGraphicsBeginImageContext (woSize);
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    [[UIColor clearColor] set];
    CGContextFillRect(ctx, NSMakeRect(0, 0, woSize.width, woSize.height));
    // draw my various images, here.
    // i.e. Various repetitions of [myImage drawAtPoint:somePoint];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

What I'm looking for is how to do that in Desktop Cocoa/NS.

Thanks!

Answer 1

NSImage* resultImage = [[[NSImage alloc] initWithSize:imageSize] autorelease];
[resultImage lockFocus];

[anotherImage drawAtPoint:aPoint fromRect:NSZeroRect operation:NSCompositeSourceOver fraction:1.0];
// Or any of the other about 6 options; see Apple's guide to pick.

[resultImage unlockFocus];

Check Apple's Drawing Guide for a much longer, more detailed answer.