c# сравнение изображений

С данной проблемой поможет справится AForge.NET

Нужно установить nuget пакет

Install-Package AForge.Imaging -Version 2.2.5

Вот пример небольшой програмки WinForms сравнивающей 2 изображения: одно маленькое, другое побольше.

using AForge.Imaging;
using System;
using System.Drawing;
using System.Windows.Forms;
namespace FileComparerWinForms
{
   public partial class Form1 : Form
   {
    private string largeFileName;
    private string smallFileName;
    private bool img1Selected;
    private bool img2Selected;
    public Form1()
    {
        InitializeComponent();
    }
    private void Form1_Load(object sender, EventArgs e)
    {
        largePicBox.Visible = false;
        smallPicBox.Visible = false;
        btnCompare.Enabled = false;
        ShowStatus("");
    }
    private void LinkLarge_Clicked(object sender, LinkLabelLinkClickedEventArgs e)
    {
        fileDialog.FileName = "";
        fileDialog.Title = "Select large image";
        fileDialog.Filter = "All images|*.jpg; *.bmp; *.png";
        fileDialog.ShowDialog();
        if (fileDialog.FileName.ToString() != "")
        {
            largeFileName = fileDialog.FileName.ToString();
            largeLink.Text = largeFileName;
            largePicBox.Image = System.Drawing.Image.FromFile(largeFileName);
            largePicBox.Visible = true;
            img1Selected = true;
        }
        ValidateSelections();
    }
    private void LinkSmall_Clicked(object sender, LinkLabelLinkClickedEventArgs e)
    {
        fileDialog.FileName = "";
        fileDialog.Title = "Select small image";
        fileDialog.Filter = "All images|*.jpg; *.bmp; *.png";
        fileDialog.ShowDialog();
        if (fileDialog.FileName.ToString() != "")
        {
            smallFileName = fileDialog.FileName.ToString();
            smallLink.Text = smallFileName;
            smallPicBox.Image = System.Drawing.Image.FromFile(smallFileName);
            smallPicBox.Visible = true;
            img2Selected = true;
        }
        ValidateSelections();
    }
    private void ValidateSelections()
    {
        ShowStatus("");
        if (img1Selected && img2Selected)
        {
            btnCompare.Enabled = true;
        }
    }
    private void CompareBtn_Click(object sender, EventArgs e)
    {
        ShowStatus("Processing...");
        Bitmap largeImage = (Bitmap)Bitmap.FromFile(largeFileName);
        Bitmap smallImage = (Bitmap)Bitmap.FromFile(smallFileName);
        // create template matching algorithm's instance
        // (set similarity threshold to 90%)
        ExhaustiveTemplateMatching tm = new ExhaustiveTemplateMatching(0.9f);
        // find all matchings with specified above similarity
        TemplateMatch[] matches = tm.ProcessImage(largeImage, smallImage);
        if (matches.Length > 0)
        {
            TemplateMatch match = matches[0];
            ShowStatus("Match found at X: " + 
                match.Rectangle.Location.X + "; Y:" + 
                match.Rectangle.Location.Y);
        }
        else
        {
            ShowStatus("Match not found");
        }
    }
    private void ShowStatus(string status)
    {
        outputMessage.Text = status;
        outputMessage.Invalidate();
        outputMessage.Update();
        outputMessage.Refresh();
    }
 }
}