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I have created a very simple test project to try and get this to work.

In the main.nib I created a borderless General/NSImageView, which I then connected to an outlet in an General/AppController I created. The implementation for my General/AppController looks like this

@implementation General/AppController

What i was hoping was that the image I set to appear inside the General/NSImageView would become transparent and I would see the image looking through to the background of the window. If you look at any apple installer you will see what I am talking about. A screenshot of what I am aiming for is included below

You might try subclassing General/NSImageView to return NO for -isOpaque. Don’t know if this will work, but it’s a shot.

I tried subclassing and overriding the return value on this method but to no avail. It seems that the drawInRect:fromRect:operation:fraction: method doesn’t have any effect at all. To prove this I tried changing the fromRect to something arbitarilly smaller than it should be and it doesn’t redraw the image any smaller. What gives?

OK - So I nailed it in the end. I had already opened up the NIB from Apple’s Installer to see how it was done but I found the contents confusing. There was an object somewhere behind everything set to a custom class which was doing the work, but I couldn’t see it. I assumed wrongly that this was not a custom view. Actually, I discovered that it is possible to have a custom view that does not show in Interface Builder, if you resize it to fill the whole window and then double click it!

Anyway, now I new that the object was a subclass of General/NSImageView and I set to work trying to make my own that would do the same job. I came up with this:

/* General/JKBackgroundImage */

#import <Cocoa/Cocoa.h>

@interface General/JKBackgroundImage : General/NSImageView { General/NSImage *image; float opacity; }

#import “General/JKBackgroundImage.h”

@implementation General/JKBackgroundImage

then in my General/AppController I just set the opacity and the image and voila! I have acheived exactly the effect shown in the picture I posted.

It’s kind of wasteful to have this inherit from General/NSImageView. You get a bunch of extra clutter from General/NSImageView and General/NSControl that doesn’t affect the drawing of your view at all (and thus actually makes your view’s interface deceptive). You’d be better off with just an General/NSView subclass.