matlab,matching,vision,correspondence
This is most probably an imshow issue. The function imshow excepts the image to be in the range [0, 255] if it is a uint8, or [0.0, 1.0] if floating point. Try: imshow(min_cost, []); Note, the empty array for the second argument. This tells Matlab to figure out the scaling....
matlab,image-processing,correspondence
There are many ways to search for corresponding interest points, but they're usually based on describing each of these interest points using the characteristics of the image around them, and, for each point in one image, comparing its surrounding's characteristics to the characteristics of the surroundings of other interest points...