C# OpenCvSharp text image tilt correction based on straight line detection

Effect

project

code

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using OpenCvSharp;

namespace OpenCvSharp_基于直线检测的文本图像倾斜校正
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string path = "1.jpg";

            pictureBox1.Image = new Bitmap(path);
            Mat mat = new Mat(path);

            Mat gray = new Mat(path, ImreadModes.Grayscale);

            Mat binary = new Mat();
            Cv2.Threshold(gray, binary, 50, 255, ThresholdTypes.BinaryInv);

            Mat element = Cv2.GetStructuringElement(MorphShapes.Rect, new OpenCvSharp.Size(7, 1));

            Mat dilation = new Mat();
            Cv2.Dilate(binary, dilation, element);

            Mat cannyDst = new Mat();
            Cv2.Canny(dilation, cannyDst, 150, 200);

            Mat houghDst = new Mat();
            mat.CopyTo(houghDst);

            LineSegmentPolar[] lineing = Cv2.HoughLines(cannyDst, 1, Cv2.PI / 180, 110, 0, 0);
            Scalar color = new Scalar(0, 255, 255);

            double meanAngle = 0.0;
            int numCnt = 0;

            for (int i = 0; i < lineing.Length; i++)
            {
                double rho = lineing[i].Rho;//线长
                double theta = lineing[i].Theta;//角度

                OpenCvSharp.Point pt1 = new OpenCvSharp.Point();
                OpenCvSharp.Point pt2 = new OpenCvSharp.Point();
                double a = Math.Cos(theta);
                double b = Math.Sin(theta);
                double x0 = a * rho, y0 = b * rho;

                pt1.X = (int)Math.Round(x0 + 600 * (-b));
                pt1.Y = (int)Math.Round(y0 + 600 * a);
                pt2.X = (int)Math.Round(x0 - 600 * (-b));
                pt2.Y = (int)Math.Round(y0 - 600 * a);

                Cv2.Line(houghDst, pt1, pt2, color, 1, LineTypes.Link4);

                theta = theta * 180 / Cv2.PI - 90;

                meanAngle += theta;
                numCnt++;
            }
            //Cv2.ImShow("houghDst", houghDst);

            meanAngle /= numCnt;
            Point2f center = new Point2f(mat.Cols / 2.0f, mat.Rows / 2.0f);

            Mat warpDst = new Mat();
            Mat rot_mat = Cv2.GetRotationMatrix2D(center, meanAngle, 1.0);
            OpenCvSharp.Size dst_sz = new OpenCvSharp.Size(mat.Cols, mat.Rows);

            Cv2.WarpAffine(mat, warpDst, rot_mat, dst_sz);

            pictureBox2.Image = new Bitmap(warpDst.ToMemoryStream());
        }
    }
}

Demo download