QImage与unsigned char*的相互转换

本文实现：QImage可以直接对像素进行操作，因此利用QT的QImage将jpg图片转换为unsigned char*，并生成raw文件。同时将生成的raw数据文件利用QImage加载出来，并显示在界面Label中。

1.源码地址

Gitee项目地址

2.代码分析

• 源图片信息
  

通过deepCopyImageData函数将图片数据转化为unsigned char*的数据data，
利用SaveBytesToFile函数将data数据进行保存。

bool MainWindow::deepCopyImageData(const char* imagePath){
    QImage image(imagePath); // test image
    QByteArray bytes;
    QBuffer buffer(&bytes);
    buffer.open(QIODevice::WriteOnly);
    image.save(&buffer, "JPG");
    buffer.close();

    unsigned char *data = (unsigned char *) malloc(bytes.size());
    qDebug()<<"bytes size:"<<bytes.size()<<endl;
    memcpy(data, reinterpret_cast<unsigned char *>(bytes.data()), bytes.size());
    int byteSize = bytes.size();
    bool IsSaveSuccess =SaveBytesToFile(data,byteSize);
    if(!IsSaveSuccess){
        return false;
    }
    delete [] data;
    data = nullptr;
    return true;
}

bool MainWindow::SaveBytesToFile(unsigned char* srcData,int size)
{
    std::ofstream out;
    out.open(imageRawData,std::ios::out |std::ios::binary);
    if(!out.is_open()){
        qDebug()<<"file open failed"<<endl;
        return false;
    }
    out.write((char*)srcData,size);
    out.close();
    return true;
}

• 产生image.raw数据
  

接下来将image.raw数据利用ReadByteFromFile进行读取，并将图片在窗口的label中显示出来，通过函数ShowImage实现，并将读取出来的数据进行保存为.jpg图片。

unsigned char* MainWindow::ReadByteFromFile(const char* fileName,int& size)
{
    std::ifstream in;
    in.open(fileName,std::ios::in);
    if(!in.is_open()){
        qDebug()<<"file open failed"<<endl;
        return nullptr;
    }
    int firstPostion = in.tellg();
    in.seekg(0, std::ios::end);
    int endPostion = in.tellg();
    int len = endPostion - firstPostion;
    qDebug()<<"file length:"<<len<<endl;
    size = len;
    in.seekg(0, std::ios::beg);
    unsigned char* buf = new unsigned char[len];
    in.read((char*)buf, len);
    in.close();
    qDebug()<<"end"<<endl;
    return buf;
}

void MainWindow::ShowImage()
{
    int size;
    unsigned char* data = ReadByteFromFile(imageRawData,size);
    if(data == nullptr){
        qDebug()<<"read file success,data is NULL"<<endl;
        return;
    }
    QImage image;
    if(!image.loadFromData(data,size))
    {
        qWarning("Image loading failed");
    }
    //清空内存。
    delete []data;
    data = nullptr;
    //保存图片
    image.save(generateImagePath);
    QPixmap pixMap = QPixmap::fromImage(image);
    //pixMap size:358,441(像素大小)
    //label size:358,441
    ui->label->setGeometry(20,20,pixMap.width(),pixMap.height());
    qDebug()<<"PixMap size:"<<pixMap.width()<<","<<pixMap.height()<<endl;
    ui->label->setPixmap(pixMap);
    ui->label->setScaledContents(true);//自适应图片大小
}

3.显示效果