C# image subtraction

Psymon

I am using the attached project code which i came across on stackoverflow in order to compare a known image and then provided with the diff image i am wanting to keep the deltas and remove any matched pixels or at least set them to white or other colour?

So far with the 2 images i am using (orig.jpg, diff.jpg) i end up with an exact clone of the diff image and nothing removed? I would like to see just the new object in diff.jpg in the final image; has anyone achieved this and know a good way to get this working even if its via use of paid libraries?

Many thanks

3 Replies

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Marvin Reid5y ago
Looking at the images you provided, you can try using the CoorelationCommand provided by the LEADTOOLS SDK. This will allow you to compare images and provide you with an array of points for the correlated areas. You can then use these values and apply it to the CropCommand where the LeadRect constructor can be used to accept a LeadPoint. The CropCommand will allow you to remove the matching coorelated areas. You can try building on this code to get you started:
string path = @"orig.jpg";
RasterCodecs codecs = new RasterCodecs();
CorrelationCommand command = new CorrelationCommand();
CodecsImageInfo info = codecs.GetInformation(path, true); //number of pages

RasterImage image = codecs.Load(path);
RasterImage detectimage = codecs.Load(@"diff.jpg");

command.CorrelationImage = detectimage;
command.Threshold = 70; // can be adjusted
command.XStep = 1;
command.YStep = 1;

for (int pageNumber = 1; pageNumber <= info.TotalPages; pageNumber++) // for multiple pages
{
   command.Run(image);

   if (command.Points != null)
   {
      Console.WriteLine("Coorelated points for page: " + command.Points); // Array of Points
   }
   codecs.Load(path, pageNumber); // load next page of image
}

https://www.leadtools.com/help/sdk/v21/dh/po/correlationcommand.html
https://www.leadtools.com/help/sdk/v21/dh/l/imageprocessing-cropcommand.html
Psymon5y ago
This seems to work great, just slow so at least have something to work from.
public static Bitmap GetDiffs(Bitmap bmp1, Bitmap bmp2, Color diffColor)
{
   for (int x = 0; x < bmp1.Width; x++)
   {
      for (int y = 0; y < bmp1.Height; y++)
      {
         // Calculate the pixels' difference.
         Color color1 = bmp1.GetPixel(x, y);
         Color color2 = bmp2.GetPixel(x, y);
         int diff =
            Math.Abs(color1.R - color2.R) +
            Math.Abs(color1.G - color2.G) +
            Math.Abs(color1.B - color2.B);
         if (diff >= 32)
         {
            bmp1.SetPixel(x, y, color2);
         }
         else
            bmp1.SetPixel(x, y, Color.Transparent);
      }
   }
   return bmp1;
}
Sachin Singh5y ago
https://www.c-sharpcorner.com/uploadfile/prathore/image-comparison-using-C-Sharp/
https://dev.to/atir_tahir/how-to-compare-two-images-in-c-net-5glo