UIImage+Colorize.swift

import UIKit

extension UIImage {
	
	// colorize image with given tint color
	// this is similar to Photoshop's "Color" layer blend mode
	// this is perfect for non-greyscale source images, and images that have both highlights and shadows that should be preserved
	// white will stay white and black will stay black as the lightness of the image is preserved
	func tint(tintColor: UIColor) -> UIImage {
		
		return modifiedImage { context, rect in
			// draw black background - workaround to preserve color of partially transparent pixels
			CGContextSetBlendMode(context, .Normal)
			UIColor.blackColor().setFill()
			CGContextFillRect(context, rect)
			
			// draw original image
			CGContextSetBlendMode(context, .Normal)
			CGContextDrawImage(context, rect, self.CGImage)
			
			// tint image (loosing alpha) - the luminosity of the original image is preserved
			CGContextSetBlendMode(context, .Color)
			tintColor.setFill()
			CGContextFillRect(context, rect)
			
			// mask by alpha values of original image
			CGContextSetBlendMode(context, .DestinationIn)
			CGContextDrawImage(context, rect, self.CGImage)
		}
	}
	
	// fills the alpha channel of the source image with the given color
	// any color information except to the alpha channel will be ignored
	func fillAlpha(fillColor: UIColor) -> UIImage {
		
		return modifiedImage { context, rect in
			// draw tint color
			CGContextSetBlendMode(context, .Normal)
			fillColor.setFill()
			CGContextFillRect(context, rect)
			
			// mask by alpha values of original image
			CGContextSetBlendMode(context, .DestinationIn)
			CGContextDrawImage(context, rect, self.CGImage)
		}
	}
	
	private func modifiedImage(@noescape draw: (CGContext, CGRect) -> ()) -> UIImage {
		
		// using scale correctly preserves retina images
		UIGraphicsBeginImageContextWithOptions(size, false, scale)
		let context: CGContext! = UIGraphicsGetCurrentContext()
		assert(context != nil)
		
		// correctly rotate image
		CGContextTranslateCTM(context, 0, size.height);
		CGContextScaleCTM(context, 1.0, -1.0);
		
		let rect = CGRectMake(0.0, 0.0, size.width, size.height)
		
		draw(context, rect)
		
		let image = UIGraphicsGetImageFromCurrentImageContext()
		UIGraphicsEndImageContext()
		return image
	}
	
}

Thank you for sharing!

I forked and updated it to Swift 3's syntax: https://gist.github.com/lynfogeek/4b6ce0117fb0acdabe229f6d8759a139

not working, I used this to process batch of UIImage and use UIColor.whiteColor() or UIColor(255, 255, 255) , those images are become grey, instead of white