cvimagewidget.h

#ifndef CVIMAGEWIDGET_H
#define CVIMAGEWIDGET_H

#include <QWidget>
#include <opencv2/opencv.hpp>
#include <QImage>
#include <QPainter>
using namespace cv;

class CvImageWidget : public QWidget
{
    Q_OBJECT
public:
    explicit CvImageWidget(QWidget *parent = 0);
    QSize sizeHint() const {return qimage.size();}
    QSize minimumSizeHint() const {return qimage.size();}

signals:
    
public slots:
    void showImage(const cv::Mat& image) {
           // Convert the image to the RGB888 format
           switch (image.type()) {
           case CV_8UC1:
               cvtColor(image, tmp, CV_GRAY2RGB);
               break;
           case CV_8UC3:
               cvtColor(image, tmp, CV_BGR2RGB);
               break;
           }

           // QImage needs the data to be stored continuously in memory
           assert(tmp.isContinuous());
           // Assign OpenCV's image buffer to the QImage. Note that the bytesPerLine parameter
           // (http://qt-project.org/doc/qt-4.8/qimage.html#QImage-6) is 3*width because each pixel
           // has three bytes.
           qimage = QImage(tmp.data, tmp.cols, tmp.rows, tmp.cols*3, QImage::Format_RGB888);

           this->setFixedSize(image.cols, image.rows);

           repaint();
       }
protected:
    void paintEvent(QPaintEvent* /*event*/) {
            // Display the image
            QPainter painter(this);
            painter.drawImage(QPoint(0,0), qimage);
            painter.end();
        }

    QImage qimage;
    Mat tmp;
};

#endif // CVIMAGEWIDGET_H