How to set the opacity/alpha of a UIImage?

Question

I know you can do this with a UIImageView, but can it be done to a UIImage? I want to have the animation images array property of a UIImageView to be an array of the same image but with different opacities. Thoughts?

Answer 1

I just needed to do this, but thought Steven's solution would be slow. This should hopefully use graphics HW. Create a category on UIImage:

- (UIImage *)imageByApplyingAlpha:(CGFloat) alpha {     UIGraphicsBeginImageContextWithOptions(self.size, NO, 0.0f);      CGContextRef ctx = UIGraphicsGetCurrentContext();     CGRect area = CGRectMake(0, 0, self.size.width, self.size.height);      CGContextScaleCTM(ctx, 1, -1);     CGContextTranslateCTM(ctx, 0, -area.size.height);      CGContextSetBlendMode(ctx, kCGBlendModeMultiply);      CGContextSetAlpha(ctx, alpha);      CGContextDrawImage(ctx, area, self.CGImage);      UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();      UIGraphicsEndImageContext();      return newImage; } 

Answer 2

Set the opacity of its view it is showed in.

UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageWithName:@"SomeName.png"]]; imageView.alpha = 0.5; //Alpha runs from 0.0 to 1.0 

Use this in an animation. You can change the alpha in an animation for an duration.

[UIView beginAnimations:nil context:NULL]; [UIView setAnimationDuration:1.0]; //Set alpha [UIView commitAnimations];