How to get pixel information which lies on boundary?

I have detected boundary of an object in image but now i want to get the pixel information of a pixel which lies on that boundary in the very first row as from that point i want to apply chain code for the object.Can anyone provide me help on this?

Answer 1

[Walter Roberson]

[r, c] = find(BoundaryMask);
[first_row, row_idx] = min(r);
mask_cols_in_first_row = c(row_idx);

now first_row will be a scalar that is the index of "very first row" . mask_cols_in_first_row will be a vector of column indices of the pixels in the mask in that very first row.