How do I effectively search through a matrix that represents pixels of an image?

I have an image that is read into a matrix using imread(). I would like to find these "corners" in the image.

For example,

255 255 255

255 0 0 255

255 0 0 255

The bold 0 would be a black top left corner which is surrounded by red(255).

Currently, I am doing a search that goes through each element in the matrix from top to bottom.

 for i = 1:100
    for j = 1:100
      ...
    end
 end

Is the any more efficient way to do this search? Could anyone tell me the name of the search

Thanks

[KSSV]

YOu can convert the image into gray and see...how your values be..and then search..?

[John]

Sorry, I dont see how rgb2gray would help that much? I was thinking that i need a better searching method

Thank you

Answer 1

[Nicolas Schmit]

You could vectorize the inner loop using find()