QImage和Mat相互转化

2017-04-07

QImage —> Mat

QImage cvMat2QImage(const cv::Mat& mat)
{
    // 8-bits unsigned, NO. OF CHANNELS = 1
    if(mat.type() == CV_8UC1)
    {
        QImage image(mat.cols, mat.rows, QImage::Format_Indexed8);
        // Set the color table (used to translate colour indexes to qRgb values)
        image.setColorCount(256);
        for(int i = 0; i < 256; i++)
        {
            image.setColor(i, qRgb(i, i, i));
        }
        // Copy input Mat
        uchar *pSrc = mat.data;
        for(int row = 0; row < mat.rows; row ++)
        {
            uchar *pDest = image.scanLine(row);
            memcpy(pDest, pSrc, mat.cols);
            pSrc += mat.step;
        }
        return image;
    }
    // 8-bits unsigned, NO. OF CHANNELS = 3
    else if(mat.type() == CV_8UC3)
    {
        // Copy input Mat
        const uchar *pSrc = (const uchar*)mat.data;
        // Create QImage with same dimensions as input Mat
        QImage image(pSrc, mat.cols, mat.rows, mat.step, QImage::Format_RGB888);
        return image.rgbSwapped();
    }
    else if(mat.type() == CV_8UC4)
    {
        qDebug() << "CV_8UC4";
        // Copy input Mat
        const uchar *pSrc = (const uchar*)mat.data;
        // Create QImage with same dimensions as input Mat
        QImage image(pSrc, mat.cols, mat.rows, mat.step, QImage::Format_ARGB32);
        return image.copy();
    }
    else
    {
        qDebug() << "ERROR: Mat could not be converted to QImage.";
        return QImage();
    }
}
cv::Mat QImage2cvMat(QImage image)
{
    cv::Mat mat;
    qDebug() << image.format();
    switch(image.format())
    {
    case QImage::Format_ARGB32:
    case QImage::Format_RGB32:
    case QImage::Format_ARGB32_Premultiplied:
        mat = cv::Mat(image.height(), image.width(), CV_8UC4, (void*)image.constBits(), image.bytesPerLine());
        break;
    case QImage::Format_RGB888:
        mat = cv::Mat(image.height(), image.width(), CV_8UC3, (void*)image.constBits(), image.bytesPerLine());
        cv::cvtColor(mat, mat, CV_BGR2RGB);
        break;
    case QImage::Format_Indexed8:
        mat = cv::Mat(image.height(), image.width(), CV_8UC1, (void*)image.constBits(), image.bytesPerLine());
        break;
    }
    return mat;
}

程序比较简单，就不多说明了。唯一需要注意的是cvMat 和QImage 对于RGBA 这四个分量的排列顺序是不相同的。转换的时候需要调换一下。但是Qt 的文档中说的很明确，QImage内部数据存储的方式不能保证以后永远不变。所以这个代码也不能保证一直是可用的。
下面是五个测试用例。基本上把各种常见情况都覆盖了。

void test1()
{
    cv::Mat mat = cv::imread("Q:\\Koala.jpg", cv::IMREAD_UNCHANGED);
    cv::cvtColor(mat, mat, CV_BGR2BGRA);
    QImage image = cvMat2QImage(mat);
    qDebug() << (mat.type() == CV_8UC4);
    cvNamedWindow("cvMat2QImage RGB32", CV_WINDOW_AUTOSIZE);
    imshow("cvMat2QImage RGB32", mat);
    QLabel label;
    label.setPixmap(QPixmap::fromImage(image));
    label.show();
    cv::waitKey(10000);
}
void test2()
{
    cv::Mat mat = cv::imread("Q:\\Koala.jpg", cv::IMREAD_UNCHANGED);
    cv::cvtColor(mat, mat, CV_BGR2GRAY);
    QImage image = cvMat2QImage(mat);
    cvNamedWindow("cvMat2QImage gray", CV_WINDOW_AUTOSIZE);
    imshow("cvMat2QImage gray", mat);
    QLabel label;
    label.setPixmap(QPixmap::fromImage(image));
    label.show();
    cv::waitKey(10000);
}
void test3()
{
    QImage image("Q:\\Koala.jpg");
    image = image.convertToFormat(QImage::Format_RGB32);
    cv::Mat mat = QImage2cvMat(image);
    //cv::cvtColor(mat, mat, CV_BGR2RGB);
    imshow("QImage2cvMat RGB32", mat);
    cv::waitKey(10000);
}

void test4()
{
    QImage image("Q:\\Koala.jpg");
    image = image.convertToFormat(QImage::Format_RGB888);
    cv::Mat mat = QImage2cvMat(image);
    imshow("QImage2cvMat RGB24", mat);
    cv::waitKey(10000);
}
void test5()
{
    QImage image("Q:\\Koala.jpg");
    image = image.convertToFormat(QImage::Format_Indexed8);
    cv::Mat mat = QImage2cvMat(image);
    imshow("QImage2cvMat Indexed8", mat);
    cv::waitKey(10000);
}
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    //test1();
    //test2();
    //test3();
    //test4();
    //test5();
    test1();
    return a.exec();
}

转载自QImage 与 cv::Mat 之间的相互转换