Historical tidbits about NSImage
Andrew Stone has been programming Cocoa for much longer than most of us out there. As such, he knows historical tidbits that help explain some of the oddities in Cocoa. One such is the plethora of drawing methods in Cocoa's NSImage, which Andrew Stone demystifies for us:
Before Mac OS X 10.0, NSImage would draw ignoring the current transformation matrix. Now this is fine if you have a simple list of graphics - but if you have nested layers of scaled, rotated, skewed groups, it's a royal pain in the patooti to micromanage image drawing based on depth of a hierarchy!
He's of course talking about drawAtPoint: and drawInRect:. Until now, I wasn't really aware of this difference. BTW, there's also lots of interesting info on these two calls and others in his article. Go there and read it, it'll make you a better programmer :-)
For compatibility with older applications, the existing NSImage drawing methods such as compositeToPoint: alway draw with only the origin of the image transformed. The image itself is drawn ignoring scale and rotation transforms with the origin at the lower left. While it has been possible to draw with the current transform by getting one of the image's representation and calling it's draw method, two new methods have been added to NSImage that do this for you.
|Christoph Pfisterer writes:|
Actually, if requiring Tiger is okay for the app, I'd recommend using CIImage instead of NSImage for displaying raster images (as in photos, not icons). It uses a higher quality scaling algorithm, and seems to be faster at the same time. And no fussing around with NSImageRep and strangely set image sizes. :-)