之前看到码农大佬分享的文章，感觉是个小乐子，就自己动手做了个小软件，方便还没学会PS的小伙伴们临时换背景Hhhh~
具体的步骤实现，可以参看[VS2017]图像处理——给证件照换背景

软件操作如GIF图所示：

新建Qt的项目文件~
.h中：

#include <QWidget>
#include <QDebug>

#include <QFile>
#include <QFileDialog>

#include <iostream>
using namespace std;

#include <opencv.hpp>
using namespace cv;

public:
    Widget(QWidget *parent = nullptr);
    ~Widget();

    Mat img,img_show,input_output;
    bool oldBG_Blue,oldBG_Red;
    bool newBG_Blue,newBG_Red,newBG_White;
    QImage QImg;
    Mat InputImg;

    QString file_path;
    string file;

    void DealPicture(Mat image);
    QImage cvMat2QImage(const cv::Mat& mat);
    cv::Mat QImage2cvMat(QImage image);



private slots:

    void on_radioButton_oldBG_Red_clicked();
    void on_radioButton_oldBG_Blue_clicked();
    void on_radioButton_newBG_White_clicked();
    void on_radioButton_newBG_Blue_clicked();
    void on_radioButton_newBG_Red_clicked();
    void on_pushButton_DealPicture_clicked();
void on_pushButton_SelectPicture_clicked();

.cpp中:

#include "widget.h"
#include "ui_widget.h"

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);
    oldBG_Blue = true;
    oldBG_Red = false;

    newBG_Blue = false;
    newBG_Red = false;
    newBG_White = true;
    ui->radioButton_oldBG_Blue->click();
    ui->radioButton_newBG_White->click();
}

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

void Widget::DealPicture(Mat img)
{
    Mat img1,img2,img3,img4,img5,img6;

    img1 = img;
    //变换图片格式
    cvtColor(img1, img2, COLOR_BGR2HSV);
    //imshow("hsv image", img2);

    //检测背景
    if (oldBG_Blue)
    {
        inRange(img2, Scalar(90, 70, 70), Scalar(110, 255, 255), img3);//检测蓝色背景
    }
    else if (oldBG_Red)
    {
        inRange(img2, Scalar(0, 135, 135), Scalar(180, 245, 230), img3);//检测红色背景
    }
    //imshow("mask image", img3);

    //腐蚀
    Mat element = getStructuringElement(MORPH_RECT, Size(3, 3));
    erode(img3, img4, element);
    //imshow("erode image", img4);

    //膨胀
    dilate(img4, img5, element);
    //imshow("dilate image", img5);

    //遍历换颜色
    Mat ergodic_img = img5;
    int pointR, pointG, pointB;

    for (int i = 0; i < ergodic_img.rows; i++)
    {
        for (int j = 0; j < ergodic_img.cols ; j++)
        {
            if (ergodic_img.at<uchar>(i, j) == 255)
            {
                if (newBG_Blue)
                {
                    pointR = 67, pointG = 142, pointB = 219;//背景变为蓝色
                }
                else if (newBG_Red)
                {
                    pointR = 255, pointG = 0, pointB = 0; //背景变为红色
                }
                else if (newBG_White)
                {
                    pointR = 255, pointG = 255, pointB = 255;//背景变为白色
                }

                img1.at<cv::Vec3b>(i, j)[0] = pointB;
                img1.at<cv::Vec3b>(i, j)[1] = pointG;
                img1.at<cv::Vec3b>(i, j)[2] = pointR;
            }
        }
    }

    //imshow("result image", img);

    imwrite("../result.jpg", img1);
    img_show = img1;
    cv::resize(img_show, img_show, Point(221, 316));
    QImg = cvMat2QImage(img_show);
    ui->label_new->setPixmap(QPixmap::fromImage(QImg));

}


void Widget::on_radioButton_oldBG_Red_clicked()
{
    oldBG_Red = true;
    oldBG_Blue = false;
}

void Widget::on_radioButton_oldBG_Blue_clicked()
{
    oldBG_Blue = true;
    oldBG_Red = false;
}

void Widget::on_radioButton_newBG_White_clicked()
{
    newBG_White = true;
    newBG_Blue = false;
    newBG_Red = false;
}

void Widget::on_radioButton_newBG_Blue_clicked()
{
    newBG_Blue = true;
    newBG_White = false;
    newBG_Red = false;
}

void Widget::on_radioButton_newBG_Red_clicked()
{
    newBG_Red = true;
    newBG_White = false;
    newBG_Blue = false;
}

void Widget::on_pushButton_DealPicture_clicked()
{
    img = imread(file);
    //imshow("input image" , img);
    //qDebug()<<oldBG_Blue<<"\t"<<oldBG_Red<<"\t"<<newBG_Blue<<"\t"<<newBG_Red<<"\t"<<newBG_White;
    DealPicture(img);
}

void Widget::on_pushButton_SelectPicture_clicked()
{
    file_path = QFileDialog::getOpenFileName(this,"open","../");
    if (file_path.isEmpty() ==false)
    {
        file = file_path.toStdString();

        img = imread(file);
        img_show = img;
        cv::resize(img_show, img_show, Point(221, 316));
        QImg = cvMat2QImage(img_show);
        ui->label_old->setPixmap(QPixmap::fromImage(QImg));
    }
}


QImage Widget::cvMat2QImage(const cv::Mat& mat)
{
    // 8-bits unsigned, NO. OF CHANNELS = 1
    if(mat.type() == CV_8UC1)
    {
        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;
    }
    // 8-bits unsigned, NO. OF CHANNELS = 3
    else if(mat.type() == CV_8UC3)
    {
        // Copy input Mat
        const uchar *pSrc = (const uchar*)mat.data;
        // Create QImage with same dimensions as input Mat
        QImage image(pSrc, mat.cols, mat.rows, mat.step, QImage::Format_RGB888);
        return image.rgbSwapped();
    }
    else if(mat.type() == CV_8UC4)
    {
        qDebug() << "CV_8UC4";
        // Copy input Mat
        const uchar *pSrc = (const uchar*)mat.data;
        // Create QImage with same dimensions as input Mat
        QImage image(pSrc, mat.cols, mat.rows, mat.step, QImage::Format_ARGB32);
        return image.copy();
    }
    else
    {
        qDebug() << "ERROR: Mat could not be converted to QImage.";
        return QImage();
    }
}
/*
cv::Mat Widget::QImage2cvMat(QImage image)
{
    cv::Mat mat;
    qDebug() << image.format();
    switch(image.format())
    {
    case QImage::Format_ARGB32:
    case QImage::Format_RGB32:
    case QImage::Format_ARGB32_Premultiplied:
        mat = cv::Mat(image.height(), image.width(), CV_8UC4, (void*)image.constBits(), image.bytesPerLine());
        break;
    case QImage::Format_RGB888:
        mat = cv::Mat(image.height(), image.width(), CV_8UC3, (void*)image.constBits(), image.bytesPerLine());
        cv::cvtColor(mat, mat, CV_BGR2RGB);
        break;
    case QImage::Format_Indexed8:
        mat = cv::Mat(image.height(), image.width(), CV_8UC1, (void*)image.constBits(), image.bytesPerLine());
        break;
    }
    return mat;
}
*/

.ui中：

结果展示：
原图：

改为白色背景：

改为证件蓝色背景：

改为证件红色背景：

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