getGrayImage.mm

-(UIImage*)getGrayImage:(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; 
}