How to compare two images?
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");
}
}
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.
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;
}
This compares images "literally" - all bytes need to be exactly the same. Other possibility would be to compare colours of pixels - then PixelFormat
s 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;
}
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;
}
}
}