将错误级别分析的 C++ 实现转换为 C#

问题描述

我正在尝试在 C# 中实现 Error Level Analysis。我在 C++ 中找到了使用 OpenCV 和 Python 使用 PIL 的示例，但在 C# 中找不到任何示例，因此我尝试使用 OpenCvSharp 库转换 C++ 代码。

这是我用过的例子：

// Control
int scale = 15,quality = 75;

// Image containers
cv::Mat input_image,compressed_image;

void processImage(int,void*)
{
    // Setting up parameters and JPEG compression
    std::vector<int> parameters;
    parameters.push_back(CV_IMWRITE_JPEG_QUALITY);
    parameters.push_back(quality);
    cv::imwrite("temp.jpg",input_image,parameters);

    // Reading temp image from the disk
    compressed_image = cv::imread("temp.jpg");
 
    if (compressed_image.empty())
    {
        std::cout << "> Error loading temp image" << std::endl;
        exit(EXIT_FAILURE);
    }

    cv::Mat output_image = cv::Mat::zeros(input_image.size(),CV_8UC3);

    // Compare values through matrices
    for (int row = 0; row < input_image.rows; ++row)
    {
        const uchar* ptr_input = input_image.ptr<uchar>(row);
        const uchar* ptr_compressed = compressed_image.ptr<uchar>(row);
        uchar* ptr_out = output_image.ptr<uchar>(row);
   
        for (int column = 0; column < input_image.cols; column++)
        {
            // Calc abs diff for each color channel multiplying by a scale factor
            ptr_out[0] = abs(ptr_input[0] - ptr_compressed[0]) * scale;
            ptr_out[1] = abs(ptr_input[1] - ptr_compressed[1]) * scale;
            ptr_out[2] = abs(ptr_input[2] - ptr_compressed[2]) * scale;

            ptr_input += 3;
            ptr_compressed += 3;
            ptr_out += 3;
        }
    }

    // Shows processed image
    cv::imshow("Error Level Analysis",output_image);
}

这是我目前的尝试：

[STAThread]
static void Main(string[] args)
{
    // Control
    int scale = 15;
    int quality = 75;

    string test_img_path = "";
    // Image container
    OpenFileDialog fdlg = new OpenFileDialog();
    fdlg.Title = "C# Corner Open File Dialog";
    fdlg.InitialDirectory = @"c:\Documents\Pictures";
    fdlg.Filter = "All files (*.*)|*.*|All files (*.*)|*.*";
    fdlg.FilterIndex = 2;
    fdlg.RestoreDirectory = true;
    if (fdlg.ShowDialog() == DialogResult.OK)
    {
        test_img_path = fdlg.FileName;
    }

    Mat input_image = Cv2.ImRead(test_img_path);
    Mat compressed_image;
    // Setting up parameters and JPEG compression

    int[] Params = new int[2];
    Params.Append(95);
    Params.Append(50);
    Cv2.ImWrite("temp.jpg",Params);

    // Reading temp image from the disk
    compressed_image = Cv2.ImRead("temp.jpg");

    if (compressed_image.Empty())
    {
        Trace.WriteLine("File empty");
    }

    Mat output_image = Mat.Zeros(input_image.Size(),MatType.CV_8UC3);

    // Compare values through matrices
    for (int row = 0; row < input_image.Rows; ++row)
    {
        unsafe
        {
            char* ptr_input = (char*)input_image.Ptr(row);
            char* ptr_compressed = (char*)compressed_image.Ptr(row);
            char* ptr_out = (char*)output_image.Ptr(row);

            for (int column = 0; column < input_image.Cols; column++)
            {
                // Calc abs diff for each color channel multiplying by a scale factor
                ptr_out[0] = (char)((ptr_input[0] - ptr_compressed[0]) * scale);
                ptr_out[1] = (char)(Math.Abs(ptr_input[1] - ptr_compressed[1]) * scale);
                ptr_out[2] = (char)(Math.Abs(ptr_input[2] - ptr_compressed[2]) * scale);

                ptr_input += 3;
                ptr_compressed += 3;
                ptr_out += 3;
            }
        }
    }

    // Shows processed image
    Cv2.imshow("Error Level Analysis",output_image);
}

以上不会编译，并导致错误：

试图读取或写入受保护的内存。这通常表明其他内存已损坏。

任何转换方面的帮助，或使用 C# 进行 ELA 的方法，将不胜感激。

解决方法

您可以改用 EmguCV，您可以从 here 安装它。然后你可以像这样将代码转换成C#。

using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using Emgu.CV;
using Emgu.CV.CvEnum;

class Program
{
    // Control
    readonly int scale = 15,quality = 75;

    // Image containers
    Mat input_image,compressed_image;

    void ProcessImage()
    {
        // Setting up parameters and JPEG compression
        KeyValuePair<ImwriteFlags,int> parameters = new KeyValuePair<ImwriteFlags,int>(ImwriteFlags.JpegQuality,quality);
        CvInvoke.Imwrite("temp.jpg",input_image,parameters);

        // Reading temp image from the disk
        compressed_image = CvInvoke.Imread("temp.jpg");

        if (compressed_image.IsEmpty)
        {
            Console.WriteLine("> Error loading temp image");
            Environment.Exit(1);
        }

        Mat output_image = Mat.Zeros(input_image.Rows,input_image.Cols,DepthType.Cv8U,3);

        byte[] input,compressed,output;
        input = new byte[input_image.Rows* input_image.Cols* 3];
        compressed = new byte[input_image.Rows * input_image.Cols * 3];
        output = new byte[input_image.Rows * input_image.Cols * 3];
        input_image.CopyTo(input);
        compressed_image.CopyTo(compressed);

        // Compare values through matrices
        for (int row = 0; row < input_image.Rows; ++row)
            for (int column = 0; column < input_image.Cols; column++)
                for (int channel = 0; channel < 3; channel++)
                    // Calc abs diff for each color channel multiplying by a scale factor
                    output[(row * input_image.Cols + column) * 3 + channel] = (byte)(Math.Abs(input[(row * input_image.Cols + column) * 3 + channel] - compressed[(row * input_image.Cols + column) * 3 + channel]) * scale);

        byte[] t = new byte[1];  
        for (int i = 0; i < output.Length; i++)
        {
            t[0] = output[i];
            Marshal.Copy(t,output_image.DataPointer + i,1);
        }

        // Shows processed image
        CvInvoke.Imshow("Error Level Analysis",output_image); 
    }
}

,

// 控制 整数比例 = 15; 整数质量 = 75;

        // Image containers
        Mat input_image = new Mat();
        Mat compressed_image;
        // Setting up parameters and JPEG compression


        int[] Params = new int[2];
        Params.Append(95);
        Params.Append(50);
        Cv2.ImWrite("temp.jpg",Params);

        // Reading temp image from the disk
        compressed_image = Cv2.ImRead("temp.jpg");

        if (compressed_image.Empty())
        {
            Trace.WriteLine("File empty");
        }

        Mat output_image = Mat.Zeros(input_image.Size(),MatType.CV_8UC3);

        // Compare values through matrices
        for (int row = 0; row < input_image.Rows; ++row)
        {
            unsafe
            {
                char* ptr_input = (char*)input_image.Ptr(row);
                char* ptr_compressed = (char*)compressed_image.Ptr(row);
                char* ptr_out = (char*)output_image.Ptr(row);

                for (int column = 0; column < input_image.Cols; column++)
                {
                    // Calc abs diff for each color channel multiplying by a scale factor
                    ptr_out[0] = (char)((ptr_input[0] - ptr_compressed[0]) * scale);
                    ptr_out[1] = (char)(Math.Abs(ptr_input[1] - ptr_compressed[1]) * scale);
                    ptr_out[2] = (char)(Math.Abs(ptr_input[2] - ptr_compressed[2]) * scale);

                    ptr_input += 3;
                    ptr_compressed += 3;
                    ptr_out += 3;
                }
            }

        }

        // Shows processed image
        Cv2.ImShow("Error Level Analysis",output_image);

,

可以通过以下代码访问像素值。您不能通过指针访问受保护的内存。

using Mat mat = new Mat(FilePath.Image.Lenna,ImreadModes.Color);
            for (int y = 0; y < mat.Height; y++)
            {
                for (int x = 0; x < mat.Width; x++)
                {
                    Vec3b color = mat.Get<Vec3b>(y,x);
                    Vec3b newColor = new Vec3b(color.Item2,color.Item1,color.Item0);
                    mat.Set<Vec3b>(y,x,newColor);
                }
            }

有很多关于如何在c#中使用opencv的例子。检查here。