图片去色

-(UIImage *)grayImage:(UIImage *)sourceImage

{

    int bitmapInfo = kCGImageAlphaNone;

    int width = sourceImage.size.width;

    int hight = sourceImage.size.height;

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();

    CGContextRef contect = CGBitmapContextCreate(nil, width, hight, 8, 0, colorSpace, bitmapInfo);

    CGColorSpaceRelease(colorSpace);

    if (contect == NULL) {

        return nil;

    }

    CGContextDrawImage(contect, CGRectMake(0, 0, width, hight), sourceImage.CGImage);

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

    CGContextRelease(contect);

    return grayImage;

}