QT中的QImage、QPixmap和opencv 中的mat转化

原文地址：https://blog.csdn.net/qq_17550379/article/details/78683153

我们使用QT和opencv的过程中经常会碰到这样的问题：Mat怎么转化位QImage？Mat怎么转化为QPixmap？今天我来告诉大家一个比较好的解决方案（以下代码参考了别人的，增加了一些修改）

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

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

namespace CVS 
{
// 将Mat转化位QImage
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 );//Format_Alpha8 and Format_Grayscale8 were added in Qt 5.5
#else//这里还有一种写法，最后给出
        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() << "CVS::cvMatToQImage() - cv::Mat image type not handled in switch:" << inMat.type();
        break;
    }

    return QImage();
}

//将Mat转化为QPixmap
inline QPixmap cvMatToQPixmap( const cv::Mat &inMat )
{
    return QPixmap::fromImage( cvMatToQImage( inMat ) );
}
//将QImage转化为Mat
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() << "CVS::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() << "CVS::QImageToCvMat() - QImage format not handled in switch:" << inImage.format();
        break;
    }

    return cv::Mat();
}

//将QPixmap转化为Mat
inline cv::Mat QPixmapToCvMat( const QPixmap &inPixmap, bool inCloneImageData = true )
{
    return QImageToCvMat( inPixmap.toImage(), inCloneImageData );
}
}

//CV_8UC1另一种写法，不过我觉得上面的一种写法更优雅^_^
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;  

新建一个头文件，将代码（CV_8UC1你自己挑一个吧）添加进去。

如何调用函数？在你要调函数的.cpp文件中添加using namespace CVS;即可。我推荐你这样去做CVS::函数。