Image_utils.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Emgu.CV;
using Emgu.CV.Util;
using Emgu.CV.Structure;
using System.Drawing;
using Emgu.CV.CvEnum;


namespace ANPR_System
{
    /// <summary>
    /// This class contain functions for image processing
    /// </summary>
    public class Image_utils
    {
        #region preprocessing functions
        /// <summary>
        /// 
        /// </summary>
        /// <param name="input_image"></param>
        /// <returns></returns>
        public static Image<Gray, byte> gaussian_blur(Image<Gray, byte> input_image)
        {
            Image<Gray, byte> output_image = input_image.SmoothGaussian(7);

            return output_image;
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="input_image"></param>
        /// <returns></returns>
        public static Image<Gray, float> sobel_X(Image<Gray, byte> input_image)
        {
            Image<Gray, float> output_image = input_image.Sobel(1, 0, 3);
            output_image = output_image.ThresholdBinary(new Gray(100), new Gray(255));
            //CvInvoke.BitwiseNot(output_image, output_image);

            return output_image;
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="input_image"></param>
        /// <returns></returns>
        public static Image<Gray, byte> adaptive_threshold(Image<Gray, byte> input_image)
        {
            Image<Gray, byte> output_image = input_image.ThresholdAdaptive(new Gray(255), AdaptiveThresholdType.GaussianC, ThresholdType.BinaryInv, 11, new Gray(2));

            return output_image;
        }

        /// <summary>
        /// Implement Binary and then Otsu threshold
        /// </summary>
        /// <param name="input_image"></param>
        /// <returns></returns>
        public static Image<Gray, byte> threshold(Image<Gray, byte> input_image)
        {
            Image<Gray, byte> binary_thresh = new Image<Gray, byte>(input_image.Width, input_image.Height);
            CvInvoke.Threshold(input_image, binary_thresh, 0, 255, ThresholdType.Binary);

            Image<Gray, byte> output_image = new Image<Gray, byte>(input_image.Width, input_image.Height);
            CvInvoke.Threshold(binary_thresh, output_image, 0, 255, ThresholdType.Otsu);

            return output_image;
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="input_image"></param>
        /// <returns></returns>
        public static Image<Gray, byte> morphology_ex(Image<Gray, byte> input_image, Plate_feature.type_of_plate type)
        {
            Mat structure = new Mat();

            if (type == Plate_feature.type_of_plate.RECT_PLATE)
            {
                structure = CvInvoke.GetStructuringElement(Emgu.CV.CvEnum.ElementShape.Rectangle, new Size(22,3), new Point(-1, -1));
            }
            else if (type == Plate_feature.type_of_plate.SQUARE_PLATE)
            {
                structure = CvInvoke.GetStructuringElement(Emgu.CV.CvEnum.ElementShape.Rectangle, new Size(26, 5), new Point(-1, -1));
            }

            Image<Gray, byte> output_image = input_image.MorphologyEx(MorphOp.Close, structure, new Point(-1, -1), 1, BorderType.Default, new MCvScalar(0));

            return output_image;
        }

        #endregion


        #region contours and edges
        /// <summary>
        /// Find all contours in the input image 
        /// </summary>
        /// <param name="image">Image after preprocessing</param>
        /// <returns>null: if there is no contour</returns>
        public static VectorOfVectorOfPoint find_all_contours(Image<Gray, byte> image)
        {
            VectorOfVectorOfPoint contours = new VectorOfVectorOfPoint();
            Mat hier = new Mat();

            CvInvoke.FindContours(image, contours, hier, RetrType.Tree, ChainApproxMethod.ChainApproxSimple);

            //for (int i = 0; i < contours.Size; i++)
            //{
            //    CvInvoke.DrawContours(img, contours, i, new MCvScalar(255, 0, 0), 2);
            //}
            if (contours.Size == 0)
            {
                return null;
            }
            else
            {
                return contours;
            }
        }

        #endregion

    }
}