Robinson Compass Mask

Advertisements


Robinson compass masks are another type of derrivate mask which is used for edge detection. This operator is also known as direction mask. In this operator we take one mask and rotate it in all the 8 compass major directions that are following:

  • North

  • North West

  • West

  • South West

  • South

  • South East

  • East

  • North East

There is no fixed mask. You can take any mask and you have to rotate it to find edges in all the above mentioned directions. All the masks are rotated on the bases of direction of zero columns.

For example let’s see the following mask which is in North Direction and then rotate it to make all the direction masks.

North Direction Mask

-101
-202
-101

North West Direction Mask

012
-101
-2-10

West Direction Mask

121
000
-1-2-1

South West Direction Mask

210
10-1
0-1-2

South Direction Mask

10-1
20-2
10-1

South East Direction Mask

0-1-2
10-1
210

East Direction Mask

-1-2-1
000
121

North East Direction Mask

-2-10
-101
012

As you can see that all the directions are covered on the basis of zeros direction. Each mask will give you the edges on its direction. Now let’s see the result of the entire above masks. Suppose we have a sample picture from which we have to find all the edges. Here is our sample picture:

Sample Picture:

Robinson Compass Mask

Now we will apply all the above filters on this image and we get the following result.

North Direction Edges

Robinson Compass Mask

North West Direction Edges

Robinson Compass Mask

West Direction Edges

Robinson Compass Mask

South West Direction Edges

Robinson Compass Mask

South Direction Edges

Robinson Compass Mask

South East Direction Edges

Robinson Compass Mask

East Direction Edges

Robinson Compass Mask

North East Direction Edges

Robinson Compass Mask

As you can see that by applying all the above masks you will get edges in all the direction. Result is also depends on the image. Suppose there is an image, which do not have any North East direction edges so then that mask will be ineffective.



Advertisements
Advertisements