UIImage category to produce a new all white image from any other image. Useful to create white versions of darker icons for use in dark views.

UIImage+WhiteImage.m

//
//  UIImage+WhiteImage.m
//
//  Created by David Hoerl on 9/14/11.
//  Copyright (c) 2011 David Hoerl. All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//

#import "UIImage+WhiteImage.h"

#if ! __has_feature(objc_arc)
#error This code requires ARC.
#endif

@implementation UIImage (WhiteImage)

- (UIImage *)whiteImage
{
	CGRect r;
	
	r.origin.x = r.origin.y = 0;
	r.size = [self size];
	
	UIGraphicsBeginImageContextWithOptions(r.size, NO, 0);
	CGContextRef context = UIGraphicsGetCurrentContext();
	CGContextSetInterpolationQuality(context,  kCGInterpolationHigh);	// in case an icon size is reduced

	CGContextClipToMask(context, r, [self CGImage]);
	
	CGContextSetFillColorWithColor(context, [[UIColor whiteColor] CGColor]);
	CGContextFillRect(context, r);
	
	UIImage *whiteImage = UIGraphicsGetImageFromCurrentImageContext();

	UIGraphicsEndImageContext();
	
	return whiteImage;
}

@end

UIImageWhiteImage.m

//
//  UIImage+WhiteImage.m
//
//  Created by David Hoerl on 9/14/11.
//  Copyright (c) 2011 David Hoerl. All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//

#import "UIImage+WhiteImage.h"

#if ! __has_feature(objc_arc)
#error This code only tested with ARC.
#endif

@implementation UIImage (WhiteImage)

- (UIImage *)whiteImage
{
	CGRect r;
	
	r.origin.x = r.origin.y = 0;
	r.size = [self size];
	
	UIGraphicsBeginImageContextWithOptions(r.size, NO, 0);
	CGContextRef context = UIGraphicsGetCurrentContext();
	CGContextSetInterpolationQuality(context,  kCGInterpolationHigh);	// in case an icon size is reduced

	CGContextClipToMask(context, r, [self CGImage]);
	
	CGContextSetFillColorWithColor(context, [[UIColor whiteColor] CGColor]);
	CGContextFillRect(context, r);
	
	UIImage *whiteImage = UIGraphicsGetImageFromCurrentImageContext();

	UIGraphicsEndImageContext();
	
	return whiteImage;
}

@end