Then you must add code to make it use thresholds to decide which locations are edges. Use a Hi Threshold and a Lo Threshold. Put both thresholds in one program and have that program produce the two new outputs. Make sure your outputs are ready for display with a $.$pgm viewer. So$,$ totally you will have $3$ outputs: $1)$ the magnitude image $2)$ the output due to Hi Threshold $3)$ the output due to Lo Threshold.