Question about NSImage and setFlipped

FROM : Joe Chan
DATE : Fri Nov 26 22:06:01 2004

I have a NSImage that I'd like to draw with NSImageInterpolationHigh
into a flipped view. So I have the following code in drawRect:

- (void)drawRect: (NSRect)rect
{
   NSImageRep    *rep = [_image bestRepresentationForDevice: nil];
   NSRect    imgRect = {0, 0};
   imgSize.size = [_image size];
   NSImage *copy = [[NSImage alloc] initWithSize: imgRect.size];
   [copy lockFocus];
   [[NSGraphicsContext currentContext] setImageInterpolation:
_imageInterpolation];
   [rep drawInRect: imgRect];
   [copy unlockFocus];
   [copy setFlipped: [self isFlipped]];
   [copy drawInRect: [self bounds] fromRect:
         operation: NSCompositeSourceOver fraction: 1.0];
   [copy release];
}

Which resulted in the image being drawn upside down. However, if I
setFlipped before [copy lockFocus], it'll work properly. Reading the
docs seems to imply that NSImage only uses the value passed into
setFlipped for drawing into a view. Why must I setFlipped before
drawing into the new NSImage for it to be drawn correctly?


-----------
Joe Chan
<email_removed>
http://www.firstian.com