Image Processing

A Statistical Analysis of the Susan Algorithms as Used in AUViking

Revision 1.0

Design Project CENG499

By

Zahid Rajabali (9809247)

Team Members:

Mark Campbell (9805386)

Donovan Parks (9905396)

Date

April 4, 2003

TOC

The SUSAN-corner algorithm (option –c in the SUSAN command line) was appended slightly to calculate the vector of the isosceles triangle we anticipate to have. The appended portion of the algorithm needs three points, and based on vector calculations determines which of the points are the two base points of the triangle, and which is the top of the triangle.  It then determines the midpoint of the base, and calculates a vector based on the base-midpoint and the topmost point of the triangle.  The angle calculated is relative to the image’s North vector (directly up). [This follows from the assumption that the image taken will have the top of the image in the same direction as the nose of the vehicle, but this can always be corrected once the camera is mounted.]

However, SUSAN-corner doesn’t always return exactly 3 points.  When it does, the 3 points are usually the 3 corners of the triangle.  It was found that the number of corners detected corresponded directly to what brightness threshold was used (option –t in the SUSAN command line).

Thus, various brightness thresholds were tested with various manufactured images of an isosceles triangle, pointing in different directions.  Once the crisp (undistorted) images were tested, the images were purposely degraded through various distortion methods and thresholds were measured at which the 3 correct points were detected.

The following is a simple chart / graphical representation of the results found.

INPUT

OUTPUT

STATISTICS CHART

 SUSAN options Image Type of distortion Pass/Fail Problem encountered -c -t 200 triangle_0 none pass NA -c -t 200 triangle_33 none pass NA -c -t 200 triangle_45 none pass NA -c -t 200 triangle_90 none pass NA -c -t 200 triangle_196 none pass NA -c -t 157 triangle_344 none fail 4 corners detected -c -t 158 triangle_344 none pass NA -c -t 225 triangle_344 none pass NA -c -t 226 triangle_344 none fail 1 corner detected

CORNERS VS THRESHOLD GRAPH

 INPUT OUTPUT

STATISTICS CHART

 SUSAN options Image Type of distortion Pass/Fail Problem encountered -c -t 6 triangle_196_guass.blur gaussian blur (omnidirectional blur) fail 7 corners detected -c -t 7 triangle_196_guass.blur gaussian blur (omnidirectional blur) fail 3 corners, angle off by 19 degrees; see out.guass.blur -c -t 8 triangle_196_guass.blur gaussian blur (omnidirectional blur) fail 2 corners detected -c -t 12 triangle_196_guass.blur gaussian blur (omnidirectional blur) pass NA -c -t 14 triangle_196_guass.blur gaussian blur (omnidirectional blur) fail 2 corners detected

CORNERS VS THRESHOLD GRAPH

 INPUT OUTPUT

STATISTICS CHART

 SUSAN options Image Type of distortion Pass/Fail Problem encountered -c -t 37 triangle_33_motion.blur motion blur (shift in one direction) fail 4 corners detected -c -t 38 triangle_33_motion.blur motion blur (shift in one direction) pass NA -c -t 39 triangle_33_motion.blur motion blur (shift in one direction) pass NA -c -t 40 triangle_33_motion.blur motion blur (shift in one direction) fail 2 corners detected

CORNERS VS THRESHOLD GRAPH

 INPUT OUTPUT

STATISTICS CHART

 SUSAN options Image Type of distortion Pass/Fail Problem encountered -c -t 1 triangle_344_noise noise speckles on both background and foreground fail 0 corners detected -c -t 300 triangle_344_noise noise speckles on both background and foreground fail 0 corners detected

CORNERS VS THRESHOLD GRAPH

 INPUT OUTPUT

STATISTICS CHART

 SUSAN options Image Type of distortion Pass/Fail Problem encountered -c -t 93 triangle_33_rounded.corners rounded corners fail 2 corners detected -c -t 94 triangle_33_rounded.corners rounded corners pass NA -c -t 114 triangle_33_rounded.corners rounded corners pass NA -c -t 115 triangle_33_rounded.corners rounded corners fail 2 corners detected

CORNERS VS THRESHOLD GRAPH

 INPUT OUTPUT

STATISTICS CHART

 SUSAN options Image Type of distortion Pass/Fail Problem encountered -c -t 149 triangle_196_ripples ripples like from water surface fail 4 corners detected -c -t 150 triangle_196_ripples ripples like from water surface pass NA -c -t 194 triangle_196_ripples ripples like from water surface pass NA -c -t 195 triangle_196_ripples ripples like from water surface fail 2 corners detected

CORNERS VS THRESHOLD GRAPH

 INPUT OUTPUT

STATISTICS CHART

 SUSAN options Image Type of distortion Pass/Fail Problem encountered -c -t 61 triangle_344_white.on.grey lightened background fail 4 corners detected -c -t 62 triangle_344_white.on.grey lightened background pass NA -c -t 63 triangle_344_white.on.grey lightened background fail 2 corners detected

CORNERS VS THRESHOLD GRAPH