iOS 彩色图变黑白图

//  彩色图变黑白图

+ (UIImage*)grayImage:(UIImage*)sourceImage {

    int width = sourceImage.size.width;

    int height = sourceImage.size.height;

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();

    CGContextRef context = CGBitmapContextCreate (nil, width, height,8,0, colorSpace,kCGImageAlphaNone);

    CGColorSpaceRelease(colorSpace);

    if (context ==NULL) {

        return nil;

    }

    CGContextDrawImage(context,CGRectMake(0,0, width, height), sourceImage.CGImage);

    UIImage *grayImage = [UIImage imageWithCGImage:CGBitmapContextCreateImage(context)];

    CGContextRelease(context);

    return grayImage;

}