iOS圖片變灰

圖片過濾去色

-(UIImage *)changeGrayImage:(UIImage *)oldImage
{
    int bitmapInfo = kCGImageAlphaNone;
    int width = oldImage.size.width;
    int height = oldImage.size.height;
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
    CGContextRef context = CGBitmapContextCreate (nil,
                                                  width,
                                                  height,
                                                  8,
                                                  0,
                                                  colorSpace,
                                                  bitmapInfo);
    CGColorSpaceRelease(colorSpace);
    if (context == NULL) {
        return nil;
    }
    CGContextDrawImage(context,
                       CGRectMake(0, 0, width, height), oldImage.CGImage);
    UIImage *grayImage = [UIImage imageWithCGImage:CGBitmapContextCreateImage(context)];
    CGContextRelease(context);
    return grayImage;
}