Re: image opacity?

FROM : Jim Puls
DATE : Sun May 11 21:11:46 2008

On May 11, 2008, at 1:26 AM, Michael Vannorsdel wrote:

> On May 11, 2008, at 1:03 AM, Patrick J. Collins wrote:
>

>> Does anyone happen to know how one could set the opacity of an
>> NSImageView object?  I am looking for a way to simply fade in an 
>> image
>> on within my app's window-- but neither of the NSImageView nor
>> IKImageView list anything about opacity...

>


> NSView and subclasses have a setAlphaValue: that might do what you 
> want.  It requires a backing Core Animation layer (CALayer) and 
> therefore is Leopard only.  You can have IB setup the layer backing 
> by setting the view's Wants Core Animation Layer under Effects of 
> the Inspector window; I think Content View is the one to enable it 
> on.  You can do it programatically with setWantsLayer:YES as well. 
> Then you use the animator proxy like:
>
> [[NSAnimationContext currentContext] setDuration:2.0];  //2 second 
> fade
> [[imageView animator] setAlphaValue:1.0f];  //fade in view to full 
> opacity
>
> Alternately you can subclass the NSImageView or make your own NSView 
> subclass and override drawRect: to vary the drawn image's opacity. 
> If you're adventurous you can use Core Image to do an accelerated 
> fade for Tiger and up.


Or, for the particular case of fading in and out, you can always use 
NSViewAnimation: http://developer.apple.com/documentation/Cocoa/Reference/ApplicationKit/Classes/NSViewAnimation_Class/Reference/Reference.html

-> jp