C#实现图像水印防篡改或去除的关键策略和方法

using System;
using System.Drawing;
using System.Drawing.Imaging;

public class DCTWatermarker
{
    public void EmbedWatermark(string imagePath, string outputImagePath, string watermarkText)
    {
        Bitmap image = new Bitmap(imagePath);
        int width = image.Width;
        int height = image.Height;

        // 将图像分块为8x8的DCT块
        for (int y = 0; y < height; y += 8)
        {
            for (int x = 0; x < width; x += 8)
            {
                Rectangle blockRect = new Rectangle(x, y, 8, 8);
                Bitmap block = image.Clone(blockRect, PixelFormat.Format24bppRgb);

                // 对每个块进行DCT变换
                double[,] dcta = DCT(block);

                // 在DCT系数中嵌入水印（例如修改特定位置的系数）
                for (int i = 0; i < 8; i++)
                {
                    for (int j = 0; j < 8; j++)
                    {
                        if (i * j < watermarkText.Length) // 示例逻辑
                        {
                            dcta[i, j] += 5; // 调整系数值
                        }
                    }
                }

                // IDCT逆变换并覆盖原块
                Bitmap modifiedBlock = IDCT(dcta);
                Graphics g = Graphics.FromImage(image);
                g.DrawImage(modifiedBlock, x, y);
                g.Dispose();
                modifiedBlock.Dispose();
            }
        }

        image.Save(outputImagePath, ImageFormat.Jpeg);
        image.Dispose();
    }

    // 简化的DCT和IDCT实现（需完整数学公式支持）
    private double[,] DCT(Bitmap block) { /* ... */ }
    private Bitmap IDCT(double[,] dcta) { /* ... */ }
}

public void EmbedLSBWatermark(string imagePath, string outputImagePath, byte[] watermark)
{
    Bitmap image = new Bitmap(imagePath);
    int index = 0;

    for (int y = 0; y < image.Height && index < watermark.Length; y++)
    {
        for (int x = 0; x < image.Width && index < watermark.Length; x++)
        {
            Color pixel = image.GetPixel(x, y);
            byte r = (byte)((pixel.R & 0xFE) | ((watermark[index] >> 7) & 0x01)); // 修改第1位
            byte g = (byte)((pixel.G & 0xFE) | ((watermark[index] >> 6) & 0x01)); // 修改第2位
            byte b = (byte)((pixel.B & 0xFE) | ((watermark[index] >> 5) & 0x01)); // 修改第3位
            index += 1;
            image.SetPixel(x, y, Color.FromArgb(r, g, b));
        }
    }

    image.Save(outputImagePath, ImageFormat.Png);
    image.Dispose();
}

// 调用外部Python服务生成水印
ProcessStartInfo psi = new ProcessStartInfo("python", "generate_watermark.py")
{
    RedirectStandardOutput = true,
    UseShellExecute = false,
    CreateNoWindow = true
};
Process process = Process.Start(psi);
string watermarkData = process.StandardOutput.ReadToEnd(); // 获取水印数据

// 将水印嵌入图像（结合DCT或其他算法）
EmbedWatermarkUsingDCT(imagePath, watermarkData);