Qt-OpenCV study notes--two-dimensional code (QR) recognition

I. Overview

QR code (Quick Response Code) is a type of two-dimensional code, which encodes data by encoding binary bits through black and white marks in a square two-digit matrix. It was first invented for tracking parts in the Japanese automobile manufacturing industry.

Two, function

detect()

Function:

Detects a QR code in an image and obtains a quadrilateral containing the code.

If the detection fails, or there are multiple QR codes in the image, the return value is false.

bool cv::QRCodeDetector::detect
(    
    InputArray    img,
    OutputArray   points 
)    

img	Load image, grayscale or color (BGR)
points	Get the vertex coordinates of the smallest quadrilateral of the QR code

decode()

Function:

Detect the QR code through detect(), and then call decode() to decode it.

Returns the UTF8-encoded output string or the empty string if it cannot be decoded.

std::string cv::QRCodeDetector::decode
(
    InputArray     img,
    InputArray     points,
    OutputArray    straight_qrcode = noArray() 
)    

img	Grayscale or color (BGR) image containing the QR code.
points	The quadrilateral vertices found by the decode() method (or other algorithm).
straight_qrcode	Obtain rectified and binarized QR code image.

detectAndDecode()

Function:

Detect and decode QR codes.

std::string cv::QRCodeDetector::detectAndDecode
(
    InputArray      img,
    OutputArray     points = noArray(),
    OutputArray     straight_qrcode = noArray() 
)    

img	Grayscale or color (BGR) image containing the QR code.
points	Gets the vertex coordinates of the smallest quadrilateral of the QR code; null if not found.
straight_qrcode	Obtain rectified and binarized QR code image.

3. Test code

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

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/objdetect.hpp>

#include <iostream>
#include <QDebug>

using namespace cv;
using namespace std;

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);

    //载入图像
    Mat src = imread("./photo/ma3.jpg",0);
    //显示图像
    imshow("src",src);

    //创建检测器
    QRCodeDetector detector;

    //检测标识
    bool sign;
    //二维码最小四边形的顶点坐标
    vector<Point> points;
    //检测二维码
    sign = detector.detect(src,points);
    //判断检测是否成功，如果成功，打印顶点坐标
    if(sign)
    {
        for (unsigned int i = 0;i<points.size();i++)
        {
            qDebug() << points[i].x;
            qDebug() << points[i].y;
        }
    }
    else
    {
        qDebug() << "检测失败！";
    }

    //解码
    string infomation1;
    Mat dst;
    infomation1 = detector.decode(src,points,dst);
    imshow("dst",dst);
    //打印解码信息
    QString str1 = QString::fromStdString(infomation1);
    qDebug() << str1;


    //第二种方法：
    string infomation2;
    vector<Point> pt;
    infomation2 = detector.detectAndDecode(src,pt);
    //打印解码信息
    QString str2 = QString::fromStdString(infomation2);
    qDebug() << str2;

}

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

4. Test results

5. Reference

Two-dimensional code recognition of Opencv---QRCodeDetector

Two-dimensional code (QR code)

QR code detection