indexing for pixel location not value

I would like to index for the pixel location value, not value of the pixel in that location. So, for example I have determined the locations on a binary image which are of importance to me, or as "regions of interest":

The first column vector (1, _) with values (the object) conatins a max and min y value in the above; (1,11) & (1,14) respectively. In order to write an algorithm to identify these points I would like to index for first column vector containing the object, then, return an output with the max and min Y value pixels, and then make them unique (change value, or color, or label them). Similarly the last column, first row, and last row end-points (with non-zero values) are all of interst in defining points for morphometric analysis/inter-landmark distance.

In summary, I am trying to create a label matrix by converting all of the points of interest to something different, or removing all pixels that are not of interest. The f(x,y) need to be values not place holders. Thinking it has something to do with dot notation, writing it out helped. Thanks