QQ：609162385
https://blog.csdn.net/cqltbe131421
直接上程式碼：

Mat MainWindow::applyLookUp(const cv::Mat& image, const cv::Mat& lookup) {
    Mat result;
    cv::LUT(image, lookup, result);
    return result;
}
void MainWindow::LutFunc(Mat &I)
{
    Mat lut(1, 256, CV_8U);
    for (int i = 0; i < 256; i++) {
        lut.at<uchar>(i) = 255 - i;
    }
    I = applyLookUp(I, lut);
}

void MainWindow::AtFunc(Mat &I)
{
    for (int i = 0; i < I.rows; ++i)
        for (int j = 0; j < I.cols; ++j)
            I.at<uchar>(i, j) = 255 - I.at<uchar>(i, j);
}

void MainWindow::PtrFunc(Mat &I)
{
    for (int i = 0; i < I.rows; ++i)
    {
        uchar *p = I.ptr<uchar>(i);
        for (int j = 0; j < I.cols; ++j)
        {
            p[j] = 255 - p[j];
        }
    }
}

void MainWindow::IteratorFunc(Mat &I)
{
    MatIterator_<uchar> it, end;
    for (it = I.begin<uchar>(), end = I.end<uchar>(); it != end; ++it)
        *it = 255 - *it;
}