写了个程序，可在途图片，并切换成灰度图及伪彩图显示，主要代码如下：

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    initRGBTable();//初始化颜色表
}

MainWindow::~MainWindow()
{
    delete ui;
}


void MainWindow::on_pushButton_2_clicked()//
{
    double fMax=0.0;
    double fMin=0.0;
    findMaxMin(m_vData,fMax,fMin);
    double fDifference = fMax - fMin;
    QVector<quint8> vnData;
    vnData.resize(m_vData.size());
    if(fDifference != 0)
    {
        for(int i = 0;i<m_nHeight;i++)
        {
            for(int j = 0;j<m_nWidth;j++)
            {
                vnData[i*m_nWidth+j] = static_cast<int>((m_vData.value(i*m_nWidth+j)-fMin)*1.0f/fDifference*255);
            }
        }
    }
    QImage img((uchar*)(&vnData[0]),m_nWidth,m_nHeight,QImage::Format_Indexed8);
    img.setColorTable(m_vecGrayTable);
    ShowImg(img);
}
void MainWindow::findMaxMin(QVector<double> vData, double &fMax, double &fMin)
{
    if(vData.size()>1)
    {
        fMax = vData.value(0);
        fMin = fMax;
        for(int i=1;i<vData.size();i++)
        {
            if(fMax<vData.value(i))
            {
                fMax = vData.value(i);
            }
            if(fMin>vData.value(i))
            {
                fMin = vData.value(i);
            }
        }
    }
}

void MainWindow::ShowImg(QImage img)
{
    QPixmap qPix = QPixmap::fromImage(img);
    qPix.scaled(ui->label->size(), Qt::KeepAspectRatio);
    ui->label->setPixmap(qPix);
}
void MainWindow::initRGBTable()
{
    //核心代码，请下载源码查看
}

void MainWindow::on_pushButton_clicked()
{
    double fMax=0.0;
    double fMin=0.0;
    findMaxMin(m_vData,fMax,fMin);
    double fDifference = fMax - fMin;
    QVector<quint8> vnData;
    vnData.resize(m_vData.size());
    if(fDifference != 0)
    {
        for(int i = 0;i<m_nHeight;i++)
        {
            for(int j = 0;j<m_nWidth;j++)
            {
                vnData[i*m_nWidth+j] = static_cast<int>((m_vData.value(i*m_nWidth+j)-fMin)*1.0f/fDifference*255);
            }
        }
    }
    QImage img((uchar*)(&vnData[0]),m_nWidth,m_nHeight,QImage::Format_Indexed8);
    img.setColorTable(m_vecColorTable);
    ShowImg(img);
}

void MainWindow::on_pushButton_3_clicked()//打开图片
{
    QFileDialog *fileDlg = new QFileDialog(this);
    fileDlg->setWindowTitle("Choose Pictures");
    QStringList qstrFilters;
    qstrFilters<<"Any files (*)";
    fileDlg->setNameFilters(qstrFilters);//设置文件过滤器
    fileDlg->setFileMode(QFileDialog::ExistingFiles);//设置能选择多个文件，如果是单个文件就写成QFileDialog::ExistingFile
    if(fileDlg->exec() == QDialog::Accepted)
    {
        QStringList strPathList = fileDlg->selectedFiles();
        if(strPathList.count()>0)
        {
            qImg.load(strPathList.first());
            m_nWidth = qImg.width();
            m_nHeight = qImg.height();
            ShowImg(qImg);
            qImg = qImg.convertToFormat(QImage::Format_Grayscale8,Qt::AutoColor);
            m_vData.resize(m_nWidth*m_nHeight);
            unsigned char *ImgDataPtr = qImg.bits();
            for(int i = 0;i<m_nHeight;i++)
            {
                for(int j = 0;j<m_nWidth;j++)
                {
                    m_vData[i*m_nWidth+j]=*ImgDataPtr;
                    ImgDataPtr++;
                }
            }
        }
    }
    fileDlg->close();
    delete fileDlg;
    fileDlg = nullptr;
}

源码下载地址：https://download.csdn.net/download/weixin_43935474/88232145