A while back I ran into a situation where I needed to be able to display an image in different parts of an app with different sizes and masks. The solution I settled on was to save one image and resize/mask it as necessary. The code below is what I used to achieve that.

// Returns a resized image
- (UIImage*)imageWithImage:(UIImage*)image scaledToSize:(CGSize)newSize {
        UIGraphicsBeginImageContext(newSize);

        [image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
        UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();

        UIGraphicsEndImageContext();

        return newImage;
}
// Returns a masked image
- (UIImage*) maskImage:(UIImage *)image withMask:(UIImage *)maskImage {

        CGImageRef maskRef = maskImage.CGImage; 

        CGImageRef mask = CGImageMaskCreate(CGImageGetWidth(maskRef),
                                        CGImageGetHeight(maskRef),
                                        CGImageGetBitsPerComponent(maskRef),
                                        CGImageGetBitsPerPixel(maskRef),
                                        CGImageGetBytesPerRow(maskRef),
                                        CGImageGetDataProvider(maskRef), NULL, false);

        CGImageRef masked = CGImageCreateWithMask([image CGImage], mask);
        CGImageRelease(mask);
        UIImage* retImage= [UIImage imageWithCGImage:masked];
        CGImageRelease(masked);
        return retImage;
}

...
UIImage *image = [UIImage imageNamed:@"myImage.png"];
UIImage *mask = [UIImage imageNamed:@"mask.png"];
UIImage *resizedImage = [self imageWithImage:image scaledToSize:CGSizeMake(76,92)];
UIImage *maskedImage = [self maskImage:resizedImage withMask:mask];

Image masking from [iPhone developer:tips];