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 *image = [UIImage imageNamed:name];
	CGRect rect = CGRectMake(0, 0, image.size.width, image.size.height);
	UIGraphicsBeginImageContextWithOptions(rect.size, NO, image.scale);
	CGContextRef c = UIGraphicsGetCurrentContext();
	[image drawInRect:rect];
	CGContextSetFillColorWithColor(c, [color CGColor]);
	CGContextSetBlendMode(c, kCGBlendModeSourceAtop);
	CGContextFillRect(c, rect);
	UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
	UIGraphicsEndImageContext();
	return result;
}

@end

Trying to figure out how to write this in AppKit: https://gist.github.com/1106004 but can't quite it.

It's a shame it doesn't allow the image to have shadows.

Thank you so much. It helped me a lot.

Thanks for this!

Question: Why no call to UIGraphicsEndImageContext() before returning? I'm not real familiar with the way graphics context works, but according to the "Creating New Images" section of the apple docs (https://developer.apple.com/library/ios/documentation/2ddrawing/conceptual/drawingprintingios/HandlingImages/Images.html#//apple_ref/doc/uid/TP40010156-CH13-SW8) you're supposed to call that when you're done to pop the context you created off the graphics stack.

faithfracture is very wise. Leaving off the UIGraphicsEndImageContext() will cause a memory leak in your application. I know, because it happened to us after a developer used this code.

Great gist. Has anyone updated/forked the above based on the last 2 comments?

If you have a UIImage instance instead of the name...

-(UIImage * _Nullable)tintMaskWithColor:(UIColor *_Nonnull)color{
    CGRect rect = CGRectMake(0, 0, self.size.width, self.size.height);
    UIGraphicsBeginImageContextWithOptions(self.size, NO, self.scale);
    CGContextRef c = UIGraphicsGetCurrentContext();
    [self drawInRect:rect];
    CGContextSetFillColorWithColor(c, [color CGColor]);
    CGContextSetBlendMode(c, kCGBlendModeSourceAtop);
    CGContextFillRect(c, rect);
    UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return result;
}