NSBitmapImageRep -initWithFocusedViewRect is doubling size of image - objective-c

Question

I have the following objective-C function meant to resize an NSBitmapImageRep to a designated size.
Currently, when working with an image of size 2048x1536 and trying to resize it to 300x225, this function keeps returning an NSBitmapImageRep of size 600x450.
- (NSBitmapImageRep*) resizeImageRep: (NSBitmapImageRep*) anOriginalImageRep toTargetSize: (NSSize) aTargetSize
{
NSImage* theTempImageRep = [[[NSImage alloc] initWithSize: aTargetSize ] autorelease];
[ theTempImageRep lockFocus ];
[NSGraphicsContext currentContext].imageInterpolation = NSImageInterpolationHigh;
NSRect theTargetRect = NSMakeRect(0.0, 0.0, aTargetSize.width, aTargetSize.height);
[ anOriginalImageRep drawInRect: theTargetRect];
NSBitmapImageRep* theResizedImageRep = [[[NSBitmapImageRep alloc] initWithFocusedViewRect: theTargetRect ] autorelease];
[ theTempImageRep unlockFocus];
return theResizedImageRep;
}
Debugging it, I'm finding that theTargetRect is of the proper size, but the call to initWithFocusedRec returns a bitmap of 600x450 pixels (high x wide)
I'm at a complete loss as to why this may be happening. Does anyone have any insight?

Answer 1

Your technique won't produce a resized image. For one thing, the method initWithFocusedViewRect:reads bitmap data from the focused window and is used to create screen grabs.
You should create a new graphics context with a new NSBitmapImageRep or NSImage of the desired size then you draw your image into that context.
Something like this.
NSGraphicsContext* context = [NSGraphicsContext graphicsContextWithBitmapImageRep:theTempImageRep];
if (context)
{
[NSGraphicsContext saveGraphicsState];
[NSGraphicsContext setCurrentContext:context];
[anOriginalImageRep drawAtPoint:NSZeroPoint];
[anOriginalImageRep drawInRect:theTargetRect];
[NSGraphicsContext restoreGraphicsState];
}
// Now your temp image rep should have the resized original.