Qt加Opencv实现 梯度矫正 功能

废话：

有时候我们是从物品的斜上方拍摄的图片，看起来不直观，需要把视角拉正，这样的一个操作就叫做 梯度矫正，需要用到的技术是 Opencv 的 透视变换。

这个只是一个简单的演示demo，如果完善一下，比如物品检测，可以应用更多的场景，比如常见的：文件、资料上传，软管摄像头的应用等，怎么说也是一个技术点吧

重要代码：

/**
* @brief hDLL_gradientAuto 梯度矫正
* @param src  输入图像
* @param dst  输出图像
* @param flag 方向,[0(左),1(上),2(右),3(下)]
* @param val  矫正度数,像素,[10 ~ 100]
* @return 0(成功)，-1(失败)
*/ 
int MainWindow::hDLL_gradientAuto(Mat &src, Mat &dst, int flag, int val)
{
    if(flag != 0 && flag != 1 && flag != 2 && flag != 3) return -1;
    if(val < 10 || val > 100) return -1;

    int width = src.cols;
    int height = src.rows;
    Mat M;
    // flag 方向,[0(左),1(上),2(右),3(下)]
    switch (flag) {
    case 0:
    {
        Point2f pts_src[] = { Point(val,val), Point(width, 0), Point(width, height), Point(val, height-val)};
        Point2f pts_dst[] = { Point(0, 0), Point(width, 0), Point(width, height) ,Point(0, height) };
        M = cv::getPerspectiveTransform(pts_src, pts_dst);
    }break;
    case 1:
    {
        Point2f pts_src[] = { Point(val,val), Point(width-val, val), Point(width, height), Point(0, height)};
        Point2f pts_dst[] = { Point(0, 0), Point(width, 0), Point(width, height) ,Point(0, height) };
        M = cv::getPerspectiveTransform(pts_src, pts_dst);
    }break;
    case 2:
    {
        Point2f pts_src[] = { Point(0,0), Point(width-val, val), Point(width-val, height-val), Point(0, height)};
        Point2f pts_dst[] = { Point(0, 0), Point(width, 0), Point(width, height) ,Point(0, height) };
        M = cv::getPerspectiveTransform(pts_src, pts_dst);
    }break;
    case 3:
    {
        Point2f pts_src[] = { Point(0,0), Point(width, 0), Point(width-val, height-val), Point(val, height-val)};
        Point2f pts_dst[] = { Point(0, 0), Point(width, 0), Point(width, height) ,Point(0, height) };
        M = cv::getPerspectiveTransform(pts_src, pts_dst);
    }break;
    }

    cv::warpPerspective(src, dst, M, dst.size(), cv::INTER_LINEAR , cv::BORDER_REPLICATE);
    return 0;
}

Demo演示：

完整代码：

.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QImage>
#include <QDebug>
#include <QtMath>

#include "opencv2/opencv.hpp"
using namespace cv;

QT_BEGIN_NAMESPACE
namespace Ui {
class MainWindow;
}
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

    void updateQLabelImage();

    Mat QImage2Mat(QImage &img);
    QImage Mat2QImage(Mat &img);

    /**
     * @brief hDLL_gradientAuto 梯度矫正
     * @param src  输入图像
     * @param dst  输出图像
     * @param flag 方向,[0(左),1(上),2(右),3(下)]
     * @param val  矫正度数,像素,[10 ~ 100]
     * @return 0(成功)，-1(失败)
     */
    int hDLL_gradientAuto(Mat &src, Mat &dst, int flag, int val);

public slots:
    void horChange(int index);
    void verChange(int index);

private:
    Ui::MainWindow *ui;

    QImage m_img;       // 原图
    QImage m_img_dst;   // 处理过的图像
};
#endif // MAINWINDOW_H

.cpp

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

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

    connect(ui->horizontalSlider, SIGNAL(valueChanged(int)), this, SLOT(horChange(int)));
    connect(ui->verticalSlider, SIGNAL(valueChanged(int)), this, SLOT(verChange(int)));

    m_img = QImage("F:1.jpg");
    m_img_dst = m_img;
    updateQLabelImage();
}

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

// 更新QLabel里面的图像
void MainWindow::updateQLabelImage()
{
    // m_img = m_img.scaled(ui->label->width(), ui->label->height());
    QImage img_show = m_img_dst.scaled(ui->label->width(), ui->label->height());
    ui->label->setPixmap(QPixmap::fromImage(img_show));
}

Mat MainWindow::QImage2Mat(QImage &img)
{
    cv::Mat mat;
    switch (img.format())
    {
    case QImage::Format_RGB32:  //一般Qt读入彩色图后为此格式
        mat = cv::Mat(img.height(), img.width(), CV_8UC4, (void*)img.constBits(), img.bytesPerLine());
        cv::cvtColor(mat,mat,cv::COLOR_BGRA2BGR);   //转3通道
        break;
    case QImage::Format_RGB888:
        mat = cv::Mat(img.height(), img.width(), CV_8UC3, (void*)img.constBits(), img.bytesPerLine());
        cv::cvtColor(mat,mat,cv::COLOR_RGB2BGR);
        break;
    case QImage::Format_Indexed8:
        mat = cv::Mat(img.height(), img.width(), CV_8UC1, (void*)img.constBits(), img.bytesPerLine());
        break;
    }
    return mat;
}

QImage MainWindow::Mat2QImage(Mat &img)
{
    if(img.type()==CV_8UC1 || img.type()==CV_8U)
    {
        QImage image((const uchar *)img.data, img.cols, img.rows, img.step, QImage::Format_Grayscale8);
        return image;
    }
    else if(img.type()==CV_8UC3)
    {
        QImage image((const uchar *)img.data, img.cols, img.rows, img.step, QImage::Format_RGB888);
        return image.rgbSwapped();  //r与b调换
    }
}

int MainWindow::hDLL_gradientAuto(Mat &src, Mat &dst, int flag, int val)
{
    if(flag != 0 && flag != 1 && flag != 2 && flag != 3) return -1;
    if(val < 10 || val > 100) return -1;

    int width = src.cols;
    int height = src.rows;
    Mat M;
    // flag 方向,[0(左),1(上),2(右),3(下)]
    switch (flag) {
    case 0:
    {
        Point2f pts_src[] = { Point(val,val), Point(width, 0), Point(width, height), Point(val, height-val)};
        Point2f pts_dst[] = { Point(0, 0), Point(width, 0), Point(width, height) ,Point(0, height) };
        M = cv::getPerspectiveTransform(pts_src, pts_dst);
    }break;
    case 1:
    {
        Point2f pts_src[] = { Point(val,val), Point(width-val, val), Point(width, height), Point(0, height)};
        Point2f pts_dst[] = { Point(0, 0), Point(width, 0), Point(width, height) ,Point(0, height) };
        M = cv::getPerspectiveTransform(pts_src, pts_dst);
    }break;
    case 2:
    {
        Point2f pts_src[] = { Point(0,0), Point(width-val, val), Point(width-val, height-val), Point(0, height)};
        Point2f pts_dst[] = { Point(0, 0), Point(width, 0), Point(width, height) ,Point(0, height) };
        M = cv::getPerspectiveTransform(pts_src, pts_dst);
    }break;
    case 3:
    {
        Point2f pts_src[] = { Point(0,0), Point(width, 0), Point(width-val, height-val), Point(val, height-val)};
        Point2f pts_dst[] = { Point(0, 0), Point(width, 0), Point(width, height) ,Point(0, height) };
        M = cv::getPerspectiveTransform(pts_src, pts_dst);
    }break;
    }

    cv::warpPerspective(src, dst, M, dst.size(), cv::INTER_LINEAR , cv::BORDER_REPLICATE);
    return 0;
}

// 横向改变
void MainWindow::horChange(int index)
{
    qDebug() << "hor:" << index;

    if(index == 0)
    {
        m_img_dst = m_img;
    }
    else if(index < 0)
    {
        int val = abs(index) * 10;
        Mat src = QImage2Mat(m_img);
        Mat dst;
        hDLL_gradientAuto(src, dst, 0, val);
        m_img_dst = Mat2QImage(dst);
    }
    else if (index > 0)
    {
        int val = abs(index) * 10;
        Mat src = QImage2Mat(m_img);
        Mat dst;
        hDLL_gradientAuto(src, dst, 2, val);
        m_img_dst = Mat2QImage(dst);
    }
    updateQLabelImage();
}

// 竖向改变
void MainWindow::verChange(int index)
{
    qDebug() << "ver:" << index;

    if(index == 0)
    {
        m_img_dst = m_img;
    }
    else if(index < 0)
    {
        int val = abs(index) * 10;
        Mat src = QImage2Mat(m_img);
        Mat dst;
        hDLL_gradientAuto(src, dst, 3, val);
        m_img_dst = Mat2QImage(dst);
    }
    else if (index > 0)
    {
        int val = abs(index) * 10;
        Mat src = QImage2Mat(m_img);
        Mat dst;
        hDLL_gradientAuto(src, dst, 1, val);
        m_img_dst = Mat2QImage(dst);
    }

    updateQLabelImage();
}

代码下载：

我的环境是：Qt 5.15.2 + Opencv V4.8.0，如果需要下载代码，自己调试，自己配置环境即可

代码仓库：https://gitee.com/vvvj/qt-test-gradient-auto