Compare image against an array of images

Question

I have an image located in

C:\ImageOne.png

And I have lets say 20 images in the directory

C:\Images

How can I compare ImageOne.png against all those images?

Example:

Imagine i got one reCaptcha image saved as C:\ImageOne.png

And in a folder located at C:\Images i have other reCaptcha images.

I then need a code that can find a identical image inside C:\Images

Current Code:

public static bool ImageCompareString(Bitmap firstImage, Bitmap secondImage)
{
    MemoryStream ms = new MemoryStream();
    firstImage.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
    String firstBitmap = Convert.ToBase64String(ms.ToArray());
    ms.Position = 0;

    secondImage.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
    String secondBitmap = Convert.ToBase64String(ms.ToArray());

    if (firstBitmap.Equals(secondBitmap))
    {
        return true;
    }
    else
    {
        return false;
    }
}

Bitmap img2 = new Bitmap(@"C:\ImageOne");

private void CheckCaptcha()
{
    foreach (string s in Directory.GetFiles(@"C:\Images"))
    {
        Bitmap img1 = new Bitmap(s);

        if (ImageCompareString(img1, img2) == true)
        {
            Logging("Identical");
        }
        else
        {
            Logging("Not Identical");
        }
        img1.Dispose();
    }
}

How precise do you want this image comparison to be? Up to every single bit? Or you need some more intelligent algorithm? — Darin Dimitrov, Dec 28 '13 at 21:54
Can you be a bit more concrete on what help you need - finding/iterating over files in a directory, reading files, comparing files as byte sequences/fuzzy image comparison or maybe even OCR and comparing resulting text? — Alexei Levenkov, Dec 28 '13 at 22:03
Imagine i have one reCaptcha image and then a folder of other reCaptcha images, i need to find a image from that folder that is identical to the first one — Merceyz, Dec 28 '13 at 22:05
`As good as possible` doesn't answer my question. You should realize that without specifying your problem precisely it will be hard to resolve it. Because you don't even know what you need to resolve. So I repeat my question once again: do you need an exact match (bit by bit comparison) or do you need some other algorithm to compare them? Also don't forget to include in your question the progress you have made so far and show the code you attempted. — Darin Dimitrov, Dec 28 '13 at 22:05
@DarinDimitrov - now with last comment the goal and necessary precision is somewhat clear - "OCR captcha" via [mechanical turk](http://en.wikipedia.org/wiki/The_Turk) :) If it is the question and approach it is to broad for SO in my opinion. — Alexei Levenkov, Dec 28 '13 at 22:07
Why do you need to find recaptcha images? This seems bogus to say the least. — Lasse V. Karlsen, Dec 28 '13 at 22:49

Selman Genç · Accepted Answer · 2013-12-28T22:40:24.827

0

Maybe this will help:

Bitmap img2 = new Bitmap(@"C:\ImageOne.png");
ImageConverter converter = new ImageConverter();
byte[] img2Bytes = (byte[])converter.ConvertTo(img2, typeof(byte[]));

foreach (string s in Directory.GetFiles(@"C:\Images"))
{
    Bitmap img1 = new Bitmap(s);
    byte[] img1Bytes = (byte[])converter.ConvertTo(img1, typeof(byte[]));
    if (CompareImages(img1Bytes,img2Bytes))
    {
        Logging("Identical");
    }
    else
    {
        Logging("Not Identical");
    }
    img1.Dispose();
}

public bool CompareImages(byte[] b1, byte[] b2)
{
   EqualityComparer<byte> comparer = EqualityComparer<byte>.Default;
   if (b1.Length == b2.Length)
   {
       for (int i = 0; i < b1.Length; i++)
       {
           if (!comparer.Equals(b1[i], b2[i])) return false;
       }
    } else { return false; }

     return true;
}

edited Dec 28 '13 at 22:40

answered Dec 28 '13 at 22:14

Selman Genç

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Still doesn't seem to work, Result is Not identical, but i know they are cus i just pasted the same image in two locations – Merceyz Dec 28 '13 at 22:22
All of them still returns as Not Identical :/ – Merceyz Dec 28 '13 at 22:33
are u sure your path is correct ? i try it for two identical images and it works fine.. – Selman Genç Dec 28 '13 at 22:33
I'm pretty sure path is correct, cus if not it would throw an error. If file is already open in another Bitmap would that cause it to fail? – Merceyz Dec 28 '13 at 22:38
What framework did you compile it with? – Merceyz Dec 28 '13 at 22:46
.NET Framework 4.5.1 why ? – Selman Genç Dec 28 '13 at 22:47
http://i.imgur.com/sbdRPjT.png – Selman Genç Dec 28 '13 at 22:49
I only have 4.5 but i assume that doesn't matter – Merceyz Dec 28 '13 at 22:49
http://puu.sh/61InM.png – Merceyz Dec 28 '13 at 22:52
@Merceyz: why don't you just try the code of Selman22? You're giving us one piece of information after the other. Images are not helpful, because we cannot change the code you give us. – Thomas Weller Dec 28 '13 at 22:56
1

@Selman22: Your code worked all the time it was that another bitmap was using the file at the same time that caused the problem, Thanks so much for your help and sorry for wasting your time :/ – Merceyz Dec 28 '13 at 23:03

Compare image against an array of images

1 Answers1