如何比较两个图像？ [英] How to compare two images?

问题描述

public void winCheck()
{
    if (button1.Image == img1)
    {
        w1 = "P2";
        button1.Image = new Bitmap(@"win_cross.png");
        button2.Image = new Bitmap(@"win_cross.png");
        button3.Image = new Bitmap(@"win_cross.png");
    }
}

下面两个 button1.Image 和 IMG1 具有相同的图像，但仍，控制不进入如果块。 是他们两个这样的任何财产，这两个值将是相同的。

Here both button1.Image and img1 have same image but still, the control doesn't go into the if block. Is their any property of both such that value of both will be same.

推荐答案

下面是一种可能做到这一点，如果你能有不安全 code，如果你希望图像恰好是在字节级别是一样的：

Here is one possibility to do it, if you can have unsafe code and if you want images to be exactly the same on byte level:

public unsafe static bool AreEqual(Bitmap b1, Bitmap b2)
{
    if (b1.Size != b2.Size)
    {
        return false;
    }

    if (b1.PixelFormat != b2.PixelFormat)
    {
        return false;
    }

    if (b1.PixelFormat != PixelFormat.Format32bppArgb)
    {
        return false;
    }

    Rectangle rect = new Rectangle(0, 0, b1.Width, b1.Height);
    BitmapData data1
        = b1.LockBits(rect, ImageLockMode.ReadOnly, b1.PixelFormat);
    BitmapData data2
        = b2.LockBits(rect, ImageLockMode.ReadOnly, b1.PixelFormat);

    int* p1 = (int*)data1.Scan0;
    int* p2 = (int*)data2.Scan0;
    int byteCount = b1.Height * data1.Stride / 4; //only Format32bppArgb 

    bool result = true;
    for (int i = 0; i < byteCount; ++i)
    {
        if (*p1++ != *p2++)
        {
            result = false;
            break;
        }
    }

    b1.UnlockBits(data1);
    b2.UnlockBits(data2);

    return result;
}

这比较形象的字面 - 所有的字节需要完全相同。另一种可能性是比较像素的颜色 - 再的PixelFormat s就不必是相同的（从的这里）：

This compares images "literally" - all bytes need to be exactly the same. Other possibility would be to compare colours of pixels - then PixelFormats wouldn't have to be the same (taken from here):

public static CompareResult Compare(Bitmap bmp1, Bitmap bmp2)
{
    CompareResult cr = CompareResult.ciCompareOk;

    //Test to see if we have the same size of image
    if (bmp1.Size != bmp2.Size)
    {
        cr = CompareResult.ciSizeMismatch;
    }
    else
    {
        //Sizes are the same so start comparing pixels
        for (int x = 0; x < bmp1.Width 
             && cr == CompareResult.ciCompareOk; x++)
        {
            for (int y = 0; y < bmp1.Height 
                         && cr == CompareResult.ciCompareOk; y++)
            {
                if (bmp1.GetPixel(x, y) != bmp2.GetPixel(x, y))
                    cr = CompareResult.ciPixelMismatch;
            }
        }
    }
    return cr;
}

这可能不过很慢。同样的链接包含比较哈希值的一个有趣的想法：

This can be however very slow. The same link contains an interesting idea of comparing hash values:

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Security.Cryptography;

namespace Imagio
{
    public class ComparingImages
    {
        public enum CompareResult
        {
            ciCompareOk,
            ciPixelMismatch,
            ciSizeMismatch
        };

        public static CompareResult Compare(Bitmap bmp1, Bitmap bmp2)
        {
            CompareResult cr = CompareResult.ciCompareOk;

            //Test to see if we have the same size of image
            if (bmp1.Size != bmp2.Size)
            {
                cr = CompareResult.ciSizeMismatch;
            }
            else
            {
                //Convert each image to a byte array
                System.Drawing.ImageConverter ic = 
                       new System.Drawing.ImageConverter();
                byte[] btImage1 = new byte[1];
                btImage1 = (byte[])ic.ConvertTo(bmp1, btImage1.GetType());
                byte[] btImage2 = new byte[1];
                btImage2 = (byte[])ic.ConvertTo(bmp2, btImage2.GetType());

                //Compute a hash for each image
                SHA256Managed shaM = new SHA256Managed();
                byte[] hash1 = shaM.ComputeHash(btImage1);
                byte[] hash2 = shaM.ComputeHash(btImage2);

                //Compare the hash values
                for (int i = 0; i < hash1.Length && i < hash2.Length 
                                  && cr == CompareResult.ciCompareOk; i++)
                {
                    if (hash1[i] != hash2[i])
                        cr = CompareResult.ciPixelMismatch;
                }
            }
            return cr;
        }
    }
}

这篇关于如何比较两个图像？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！