Creating arbitrarily-colored icons from a black-with-alpha master image (iOS)

gistfile1.c

// Usage example:
// input image: http://f.cl.ly/items/3v0S3w2B3N0p3e0I082d/Image%202011.07.22%2011:29:25%20PM.png
//
// UIImage *buttonImage = [UIImage ipMaskedImageNamed:@"UIButtonBarAction.png" color:[UIColor redColor]];

// .h
@interface UIImage (IPImageUtils)
+ (UIImage *)ipMaskedImageNamed:(NSString *)name color:(UIColor *)color;
@end

// .m
@implementation UIImage (IPImageUtils)

+ (UIImage *)ipMaskedImageNamed:(NSString *)name color:(UIColor *)color
{
    UIImage *blackWithAlphaImage = [UIImage imageNamed:name];
    CGSize size = blackWithAlphaImage.size;

    UIGraphicsBeginImageContextWithOptions(size, YES, blackWithAlphaImage.scale);
    [[UIColor whiteColor] setFill];

    CGRect rect = CGRectMake(0, 0, size.width, size.height);
    CGContextFillRect(UIGraphicsGetCurrentContext(), rect);
    [blackWithAlphaImage drawInRect:rect];
    UIImage *compositedMaskImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    CGSize unscaledSize = size;
    unscaledSize.width *= blackWithAlphaImage.scale;
    unscaledSize.height *= blackWithAlphaImage.scale;

    UIGraphicsBeginImageContext(unscaledSize);
    CGContextRef context = UIGraphicsGetCurrentContext();
    [color setFill];

    CGRect unscaledRect = CGRectMake(0, 0, unscaledSize.width, unscaledSize.height);
    CGContextFillRect(context, unscaledRect);
    UIImage *colorImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    CGImageRef compositedMaskImageRef = compositedMaskImage.CGImage; 
    CGImageRef mask = CGImageMaskCreate(
        unscaledSize.width,
        unscaledSize.height,
        CGImageGetBitsPerComponent(compositedMaskImageRef),
        CGImageGetBitsPerPixel(compositedMaskImageRef),
        CGImageGetBytesPerRow(compositedMaskImageRef),
        CGImageGetDataProvider(compositedMaskImageRef), 
        NULL, 
        false
    );

    CGImageRef masked = CGImageCreateWithMask([colorImage CGImage], mask);
    return [UIImage imageWithCGImage:masked scale:compositedMaskImage.scale orientation:UIImageOrientationUp];
}

@end