Feature Extraction and Image Processing

Appendices 341

plotedit on, title (ÔMagnitude of eye edges by Prewitt operatorÕ),

plotedit off

subplot(1,2,2), imagesc(roberts_edges);

plotedit on, title (ÔEye edges by Roberts cross operatorÕ), plotedit

off

disp (ÔWe can see that the effect of smoothing is to reduce noise inÕ)

disp (Ôthe edge detection processÕ)

pause;

disp (ÔThe direction is how the edge is changing, but this is much

lessÕ)

disp (Ôeasy to see in the displayed image.Õ)

direction=prewitt_edges(:,:,2);

imagesc(direction);

plotedit on, title (ÔDirection of eye edges by Prewitt operatorÕ),

plotedit off

pause;

Function edges=prewitt(image)

%derive edges by 3*3 Prewitt operator

%

%Usage: [new image]=prewitt(image) ...