在使用Qt和OpenCV混合編程時，我們有時需要在兩種圖片類cv::Mat和QImage之間進行轉換，下面的代碼參考了網上這個帖子：

//##### cv::Mat ---> QImage #####

// Shallow copy
QImage mat2qimage_ref(cv::Mat &m, QImage::Format format) {
    return QImage(m.data, m.cols, m.rows, m.step, format);
}

// Deep copy
QImage mat2qimage_cpy(cv::Mat &m, QImage::Format format) {
    return QImage(m.data, m.cols, m.rows, m.step, format).copy();
}

//##### QImage ---> cv::Mat #####

// Shallow copy
cv::Mat qimage2mat_ref(QImage &img, int format) {
    return cv::Mat(img.height(), img.width(), format, img.bits(), img.bytesPerLine());
}

// Deep copy
cv::Mat qimage2mat_ref(QImage &img, int format) {
    return cv::Mat(img.height(), img.width(), format, const_cast<uchar*>(img.bits()), img.bytesPerLine()).clone();
}

還可以用下面的這個代碼，參考了這個帖子：

//##### cv::Mat ---> QImage #####
QImage cvMat_to_QImage(const cv::Mat &mat ) {
  switch ( mat.type() )
  {
     // 8-bit, 4 channel
     case CV_8UC4:
     {
        QImage image( mat.data, mat.cols, mat.rows, mat.step, QImage::Format_RGB32 );
        return image;
     }

     // 8-bit, 3 channel
     case CV_8UC3:
     {
        QImage image( mat.data, mat.cols, mat.rows, mat.step, QImage::Format_RGB888 );
        return image.rgbSwapped();
     }

     // 8-bit, 1 channel
     case CV_8UC1:
     {
        static QVector<QRgb>  sColorTable;
        // only create our color table once
        if ( sColorTable.isEmpty() )
        {
           for ( int i = 0; i < 256; ++i )
              sColorTable.push_back( qRgb( i, i, i ) );
        }
        QImage image( mat.data, mat.cols, mat.rows, mat.step, QImage::Format_Indexed8 );
        image.setColorTable( sColorTable );
        return image;
     }

     default:
        qDebug("Image format is not supported: depth=%d and %d channels\n", mat.depth(), mat.channels());
        break;
  }
  return QImage();
}


//##### QImage ---> cv::Mat #####
cv::Mat QImage_to_cvMat( const QImage &image, bool inCloneImageData = true ) {
  switch ( image.format() )
  {
     // 8-bit, 4 channel
     case QImage::Format_RGB32:
     {
        cv::Mat mat( image.height(), image.width(), CV_8UC4, const_cast<uchar*>(image.bits()), image.bytesPerLine() );
        return (inCloneImageData ? mat.clone() : mat);
     }

     // 8-bit, 3 channel
     case QImage::Format_RGB888:
     {
        if ( !inCloneImageData ) {
           qWarning() << "ASM::QImageToCvMat() - Conversion requires cloning since we use a temporary QImage";
        }
        QImage swapped = image.rgbSwapped();
        return cv::Mat( swapped.height(), swapped.width(), CV_8UC3, const_cast<uchar*>(swapped.bits()), swapped.bytesPerLine() ).clone();
     }

     // 8-bit, 1 channel
     case QImage::Format_Indexed8:
     {
        cv::Mat  mat( image.height(), image.width(), CV_8UC1, const_cast<uchar*>(image.bits()), image.bytesPerLine() );

        return (inCloneImageData ? mat.clone() : mat);
     }

     default:
        qDebug("Image format is not supported: depth=%d and %d format\n", image.depth(), image.format();
        break;
  }

  return cv::Mat();
}

Convert between cv::Mat and QImage 兩種圖片類轉換