shuiyin/ShuiYinCSharp/Com/Lmc/ShuiYin/ImgWatermarkUtil.cs

using System.Collections.Generic;
using OpenCvSharp;

namespace Com.Lmc.ShuiYin
{
    public class ImgWatermarkUtil
    {
        // Changed from static fields to local to avoid thread safety issues, 
        // but to match structure I will keep them but re-initialize them or just use locals if possible.
        // The Java code reused static lists which is buggy. I will use locals.
        
        public static Mat AddImageWatermarkWithText(Mat image, string watermarkText)
        {
            Mat complexImage = new Mat();
            Mat padded = SplitSrc(image, out List<Mat> allPlanes);
            padded.ConvertTo(padded, MatType.CV_32F);
            
            List<Mat> planes = new List<Mat>();
            planes.Add(padded);
            planes.Add(Mat.Zeros(padded.Size(), MatType.CV_32F));
            
            Cv2.Merge(planes.ToArray(), complexImage);
            Cv2.Dft(complexImage, complexImage);
            
            Scalar scalar = new Scalar(0, 0, 0);
            Point point = new Point(40, 40);
            
            Cv2.PutText(complexImage, watermarkText, point, HersheyFonts.HersheyDuplex, 1.0, scalar);
            Cv2.Flip(complexImage, complexImage, FlipMode.XY);
            Cv2.PutText(complexImage, watermarkText, point, HersheyFonts.HersheyDuplex, 1.0, scalar);
            Cv2.Flip(complexImage, complexImage, FlipMode.XY);
            
            return AntitransformImage(complexImage, allPlanes);
        }

        public static Mat GetImageWatermarkWithText(Mat image)
        {
            Mat complexImage = new Mat();
            Mat padded = SplitSrc(image, out List<Mat> unused);
            padded.ConvertTo(padded, MatType.CV_32F);
            
            List<Mat> planes = new List<Mat>();
            planes.Add(padded);
            planes.Add(Mat.Zeros(padded.Size(), MatType.CV_32F));
            
            Cv2.Merge(planes.ToArray(), complexImage);
            Cv2.Dft(complexImage, complexImage);
            
            return CreateOptimizedMagnitude(complexImage);
        }

        private static Mat SplitSrc(Mat mat, out List<Mat> allPlanes)
        {
            allPlanes = new List<Mat>();
            mat = OptimizeImageDim(mat);
            Cv2.Split(mat, out Mat[] splitPlanes);
            allPlanes.AddRange(splitPlanes);
            
            Mat padded = new Mat();
            if (allPlanes.Count > 1)
            {
                padded = allPlanes[0];
            }
            else
            {
                padded = mat;
            }
            return padded;
        }

        private static Mat AntitransformImage(Mat complexImage, List<Mat> allPlanes)
        {
            Mat invDFT = new Mat();
            Cv2.Idft(complexImage, invDFT, DftFlags.Scale | DftFlags.RealOutput);
            
            Mat restoredImage = new Mat();
            invDFT.ConvertTo(restoredImage, MatType.CV_8U);
            
            if (allPlanes.Count == 0)
            {
                allPlanes.Add(restoredImage);
            }
            else
            {
                allPlanes[0] = restoredImage;
            }
            
            Mat lastImage = new Mat();
            Cv2.Merge(allPlanes.ToArray(), lastImage);
            return lastImage;
        }

        private static Mat OptimizeImageDim(Mat image)
        {
            Mat padded = new Mat();
            int addPixelRows = Cv2.GetOptimalDFTSize(image.Rows);
            int addPixelCols = Cv2.GetOptimalDFTSize(image.Cols);
            Cv2.CopyMakeBorder(image, padded, 0, addPixelRows - image.Rows, 0, addPixelCols - image.Cols,
                BorderTypes.Constant, Scalar.All(0));
            return padded;
        }

        private static Mat CreateOptimizedMagnitude(Mat complexImage)
        {
            List<Mat> newPlanes = new List<Mat>();
            Mat mag = new Mat();
            Cv2.Split(complexImage, out Mat[] splitPlanes);
            newPlanes.AddRange(splitPlanes);
            
            Cv2.Magnitude(newPlanes[0], newPlanes[1], mag);
            Cv2.Add(Mat.Ones(mag.Size(), MatType.CV_32F), mag, mag);
            Cv2.Log(mag, mag);
            
            ShiftDFT(mag);
            
            mag.ConvertTo(mag, MatType.CV_8UC1);
            Cv2.Normalize(mag, mag, 0, 255, NormTypes.MinMax, (int)MatType.CV_8UC1);
            return mag;
        }

        private static void ShiftDFT(Mat image)
        {
            image = image.SubMat(new Rect(0, 0, image.Cols & -2, image.Rows & -2));
            int cx = image.Cols / 2;
            int cy = image.Rows / 2;
            
            Mat q0 = new Mat(image, new Rect(0, 0, cx, cy));
            Mat q1 = new Mat(image, new Rect(cx, 0, cx, cy));
            Mat q2 = new Mat(image, new Rect(0, cy, cx, cy));
            Mat q3 = new Mat(image, new Rect(cx, cy, cx, cy));
            Mat tmp = new Mat();
            q0.CopyTo(tmp);
            q3.CopyTo(q0);
            tmp.CopyTo(q3);
            q1.CopyTo(tmp);
            q2.CopyTo(q1);
            tmp.CopyTo(q2);
        }
    }
}