graphic similarity measure and visualization

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I am a s/w developer. My question is how to compare two images and visualize the output by comparing its pixel matching. I also want to show the unmatched pixel area :confused::confused:

Posted 21-Oct-10 0:26am

meenavinaykumar

Updated 21-Oct-10 4:01am

Toli Cuturicu

v2

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Rajesh Anuhya · Answer 1 · 2010-10-21T01:03:00

This code may help you

try like this...

Bitmap img1 = new Bitmap("c:\\rajesh.jpg");
          Bitmap img2 = new Bitmap("c:\\rajesh.jpg");
          Color Myc1; Color Myc2;
          for (int i = 0; i < img1.Height; i++)
              for (int j = 0; j < img2.Width; j++)
              {
                  Myc1 = img1.GetPixel(i, j);
                  Myc2 = img2.GetPixel(i, j);
                  if ((Myc1.R != Myc2.R) || (Myc1.G != Myc2.G) || (Myc1.B != Myc2.B))
                      MessageBox.Show ("Found Mismatch");
              }

Chris Trelawny-Ross · Answer 2 · 2010-10-21T10:52:00

Make a copy of one of the bitmaps - so that you can modify it (in memory) without destroying your source images.

Use LockBits() on both bitmaps to get access to the raw bitmap data.

Iterate the whole bitmap array, indexing both images in parallel, comparing bytes between images. Where the bytes are the same, write 0 to the copy; where the bytes are different, write 255 to the copy.

Now, you can view the copy, and wherever the images match you'll get black and wherever they differ you'll get white.

Instead of writing 255 where bytes differ, you could write the original value - but if it has a low value, it'll be hard to tell a 'real' black pixel from a black 'pixels match' pixel.

Note that this operation assumes iterating the array as bytes. Depending on the bit-depth of the image this may be inappropriate (for example, 1 bpp images) or inconvenient (e.g. 32 bpp images, you could process a whole pixel at a time, instead of a single color component at a time).

If you can process a whole pixel at a time, there might be a 'highly improbably' color that you could use as the 'pixels match' indicator, that would be unlikely to occur in a real image.

graphic similarity measure and visualization

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