asmOpenCV.h

#ifndef ASM_OPENCV_H
#define ASM_OPENCV_H

/**
   Functions to convert between OpenCV's cv::Mat and Qt's QImage and QPixmap.

   Andy Maloney <asmaloney@gmail.com>
   https://asmaloney.com/2013/11/code/converting-between-cvmat-and-qimage-or-qpixmap
**/

#include <QDebug>
#include <QImage>
#include <QPixmap>

#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/imgproc/types_c.h"


namespace ASM {
// NOTE: This does not cover all cases - it should be easy to add new ones as required.
inline QImage  cvMatToQImage( const cv::Mat &inMat )
{
    switch ( inMat.type() )
    {
    // 8-bit, 4 channel
    case CV_8UC4:
    {
        QImage image( inMat.data,
                      inMat.cols, inMat.rows,
                      static_cast<int>(inMat.step),
                      QImage::Format_ARGB32 );

        return image;
    }

        // 8-bit, 3 channel
    case CV_8UC3:
    {
        QImage image( inMat.data,
                      inMat.cols, inMat.rows,
                      static_cast<int>(inMat.step),
                      QImage::Format_RGB888 );

        return image.rgbSwapped();
    }

        // 8-bit, 1 channel
    case CV_8UC1:
    {
#if QT_VERSION >= QT_VERSION_CHECK(5, 5, 0)
        QImage image( inMat.data,
                      inMat.cols, inMat.rows,
                      static_cast<int>(inMat.step),
                      QImage::Format_Grayscale8 );
#else
        static QVector<QRgb>  sColorTable;

        // only create our color table the first time
        if ( sColorTable.isEmpty() )
        {
            sColorTable.resize( 256 );

            for ( int i = 0; i < 256; ++i )
            {
                sColorTable[i] = qRgb( i, i, i );
            }
        }

        QImage image( inMat.data,
                      inMat.cols, inMat.rows,
                      static_cast<int>(inMat.step),
                      QImage::Format_Indexed8 );

        image.setColorTable( sColorTable );
#endif

        return image;
    }

    default:
        qWarning() << "ASM::cvMatToQImage() - cv::Mat image type not handled in switch:" << inMat.type();
        break;
    }

    return QImage();
}

inline QPixmap cvMatToQPixmap( const cv::Mat &inMat )
{
    return QPixmap::fromImage( cvMatToQImage( inMat ) );
}

// If inImage exists for the lifetime of the resulting cv::Mat, pass false to inCloneImageData to share inImage's
// data with the cv::Mat directly
//    NOTE: Format_RGB888 is an exception since we need to use a local QImage and thus must clone the data regardless
//    NOTE: This does not cover all cases - it should be easy to add new ones as required.
inline cv::Mat QImageToCvMat( const QImage &inImage, bool inCloneImageData = true )
{
    switch ( inImage.format() )
    {
    // 8-bit, 4 channel
    case QImage::Format_ARGB32:
    case QImage::Format_ARGB32_Premultiplied:
    {
        cv::Mat  mat( inImage.height(), inImage.width(),
                      CV_8UC4,
                      const_cast<uchar*>(inImage.bits()),
                      static_cast<size_t>(inImage.bytesPerLine())
                      );

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

        // 8-bit, 3 channel
    case QImage::Format_RGB32:
    case QImage::Format_RGB888:
    {
        if ( !inCloneImageData )
        {
            qWarning() << "ASM::QImageToCvMat() - Conversion requires cloning because we use a temporary QImage";
        }

        QImage   swapped = inImage;

        if ( inImage.format() == QImage::Format_RGB32 )
        {
            swapped = swapped.convertToFormat( QImage::Format_RGB888 );
        }

        swapped = swapped.rgbSwapped();

        return cv::Mat( swapped.height(), swapped.width(),
                        CV_8UC3,
                        const_cast<uchar*>(swapped.bits()),
                        static_cast<size_t>(swapped.bytesPerLine())
                        ).clone();
    }

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

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

    default:
        qWarning() << "ASM::QImageToCvMat() - QImage format not handled in switch:" << inImage.format();
        break;
    }

    return cv::Mat();
}

// If inPixmap exists for the lifetime of the resulting cv::Mat, pass false to inCloneImageData to share inPixmap's data
// with the cv::Mat directly
//    NOTE: Format_RGB888 is an exception since we need to use a local QImage and thus must clone the data regardless
inline cv::Mat QPixmapToCvMat( const QPixmap &inPixmap, bool inCloneImageData = true )
{
    return QImageToCvMat( inPixmap.toImage(), inCloneImageData );
}
}

#endif