c – 使用OpenCV的imread()从qrc中读取图像

Mat img = imread(":/TempIcons/logo.png");

Mat img = imread("qrc://TempIcons/logo.png");

正如@TheDarkKnight指出的那样,imread并不知道Qt资源.但是,您可以编写自己的加载器,使用QFile从资源中检索二进制数据,并使用imdecode(由imread内部完成)来读取图像：

Mat loadFromQrc(QString qrc,int flag = IMREAD_COLOR)
{
    //double tic = double(getTickCount());

    QFile file(qrc);
    Mat m;
    if(file.open(qiodevice::ReadOnly))
    {
        qint64 sz = file.size();
        std::vector<uchar> buf(sz);
        file.read((char*)buf.data(),sz);
        m = imdecode(buf,flag);
    }

    //double toc = (double(getTickCount()) - tic) * 1000.0 / getTickFrequency();
    //qDebug() << "OpenCV loading time: " << toc;

    return m;
}

你可以这样称呼它：

Mat m = loadFromQrc("qrc_path");

或指定一个标志：

Mat m = loadFromQrc("qrc_path",IMREAD_GRAYSCALE);

性能

我尝试使用loadFromQrc加载图像,并使用this代码加载QImage并转换为Mat,无论是否克隆. loadFromQrc的结果比加载QImage并将其转换为Mat快10倍.

结果以ms为单位：

Load Mat                :  4.85965
QImage to Mat (no clone):  49.3999
QImage to Mat (clone)   :  49.8497

测试代码：

#include <vector>
#include <iostream>
#include <QDebug>
#include <QtWidgets>

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

Mat loadFromQrc(QString qrc,int flag = IMREAD_COLOR)
{
    QFile file(qrc);
    Mat m;
    if(file.open(qiodevice::ReadOnly))
    {
        qint64 sz = file.size();

        std::vector<uchar> buf(sz);
        file.read((char*)buf.data(),flag);
    }
    return m;
}

cv::Mat QImagetoCvMat( const QImage &inImage,bool inCloneImageData = true )
{
    switch ( inImage.format() )
    {
    // 8-bit,4 channel
    case QImage::Format_RGB32:
    {
        cv::Mat  mat( inImage.height(),inImage.width(),CV_8UC4,const_cast<uchar*>(inImage.bits()),inImage.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 = inImage.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( inImage.height(),CV_8UC1,inImage.bytesPerLine() );

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

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

    return cv::Mat();
}

int main(int argc,char *argv[])
{
    QString url = "...";

    {
        double tic = double(getTickCount());

        Mat m1 = loadFromQrc(url);

        double toc = (double(getTickCount()) - tic) * 1000.0 / getTickFrequency();
        qDebug() << "Load Mat: " << toc;

        if(m1.data != NULL)
        {
            imshow("m1",m1);
            waitKey(1);
        }
    }


//    {
//        double tic = double(getTickCount());

//        QImage img;
//        img.load(url);
//        Mat m2 = QImagetoCvMat(img,false);

//        double toc = (double(getTickCount()) - tic) * 1000.0 / getTickFrequency();
//        qDebug() << "QImage to Mat (no clone): " << toc;

//        if(m2.data != NULL)
//        {
//            imshow("m2",m2);
//            waitKey(1);
//        }
//    }


//    {
//        double tic = double(getTickCount());

//        QImage img;
//        img.load(url);
//        Mat m3 = QImagetoCvMat(img,true);

//        double toc = (double(getTickCount()) - tic) * 1000.0 / getTickFrequency();
//        qDebug() << "QImage to Mat (clone): " << toc;

//        if(m3.data != NULL)
//        {
//            imshow("m3",m3);
//            waitKey(1);
//        }
//    }

    waitKey();
    return 0;
}