ExtractMrzRegion.cs

using IdApp.Cv.Arithmetics;
using IdApp.Cv.Basic;
using IdApp.Cv.Objects;
using IdApp.Cv.Transformations;
using IdApp.Cv.Transformations.Convolutions;
using IdApp.Cv.Transformations.Morphological;
using IdApp.Cv.Transformations.Thresholds;
using System;
using System.Collections.Generic;
 
namespace IdApp.Cv.Utilities
{
    public static partial class Utilities
    {
        public static Matrix<float>? ExtractMrzRegion(this Matrix<float> M)
        {
            Matrix<float> G = M.GaussianBlur(3);
            Matrix<float> ForOcr = G = G.BlackHat((13 * M.Width + 208) / 415, (5 * M.Height + 300) / 600);
            G = G.DetectEdgesSharrVertical();     // Detect vertical edges=detect horizontal changes
            G.Abs();
            G.Contrast();
            G = G.Close((13 * M.Width + 208) / 415, (5 * M.Height + 300) / 600);
            G.Threshold(G.OtsuThreshold());
 
            ObjectMap ObjectMap = G.ObjectMap(0.5f);
            ObjectInformation[] Objects = ObjectMap.Objects;
 
            Array.Sort(Objects, (o1, o2) => o1.MinY - o2.MinY);
 
            List<ushort> Found = [];
 
            foreach (ObjectInformation Object in Objects)
            {
                float Aspect = ((float)Object.Width) / Object.Height;
                if (Aspect < 5)
                    continue;
 
                float RelativeWidth = ((float)Object.Width) / G.Width;
                if (RelativeWidth < 0.75f)
                    continue;
 
                int i = (5 * Math.Max(M.Width, M.Height) + 300) / 600;
                Point[] Reduced = Object.Contour.Reduce(i);
                Point[] Reduced2 = Reduced.Reduce(i);
                if (Reduced2.Length != 4)
                    continue;
 
                Found.Add(Object.Nr);
            }
 
            if (Found.Count == 0)
                return null;
 
            Matrix<float> SubRegion = ForOcr.Region((ForOcr.Width - G.Width) / 2, (ForOcr.Height - G.Height) / 2, G.Width, G.Height);
            return ObjectMap.Extract([.. Found], SubRegion);
        }
 
        public static Matrix<int>? ExtractMrzRegion(this Matrix<int> M)
        {
            Matrix<int> G = M.GaussianBlur(3);
            Matrix<int> ForOcr = G = G.BlackHat((13 * M.Width + 208) / 415, (5 * M.Height + 300) / 600);
            G = G.DetectEdgesSharrVertical();     // Detect vertical edges=detect horizontal changes
            G.Abs();
            G.Contrast();
            G = G.Close((13 * M.Width + 208) / 415, (5 * M.Height + 300) / 600);
            G.Threshold(G.OtsuThreshold());
 
            ObjectMap ObjectMap = G.ObjectMap(0x800000);
            ObjectInformation[] Objects = ObjectMap.Objects;
 
            Array.Sort(Objects, (o1, o2) => o1.MinY - o2.MinY);
 
            List<ushort> Found = [];
 
            foreach (ObjectInformation Object in Objects)
            {
                float Aspect = ((float)Object.Width) / Object.Height;
                if (Aspect < 5)
                    continue;
 
                float RelativeWidth = ((float)Object.Width) / G.Width;
                if (RelativeWidth < 0.75f)
                    continue;
 
                //int i = (5 * Math.Max(M.Width, M.Height) + 300) / 600;
                //Point[] Reduced = Object.Contour.Reduce(i);
                //Point[] Reduced2 = Reduced.Reduce(i);
                //if (Reduced2.Length != 4)
                //  continue;
 
                Found.Add(Object.Nr);
            }
 
            if (Found.Count == 0)
                return null;
 
            Matrix<int> SubRegion = ForOcr.Region((ForOcr.Width - G.Width) / 2, (ForOcr.Height - G.Height) / 2, G.Width, G.Height);
            return ObjectMap.Extract([.. Found], SubRegion);
        }
    }
}