I am trying to implement the canny edge detector. I have made some code which generates what I think should be correct up to the non-maxima suppression stage, however when I run it I get an image that just about shows the outlines, but is not my expected result.
I have spent hours trying to fix it, but can't find where I have gone wrong. Can anyone point me in the right direction?
% Set direction to either 0, 45, -45 or 90 depending on angle. [x,y]=size(f1); for i=1:x-1, for j=1:y-1, if ((gradAngle(i,j)>67.5 && gradAngle(i,j)<=90) || (gradAngle(i,j)>=-90 && gradAngle(i,j)<=-67.5)) gradDirection(i,j)=0; elseif ((gradAngle(i,j)>22.5 && gradAngle(i,j)<=67.5)) gradDirection(i,j)=45; elseif ((gradAngle(i,j)>-22.5 && gradAngle(i,j)<=22.5)) gradDirection(i,j)=90; elseif ((gradAngle(i,j)>-67.5 && gradAngle(i,j)<=-22.5)) gradDirection(i,j)=-45; end end end % Non-maxima suppression. % Compare to neighbours and set as 0 if smaller than either of them for i=2:x-2, for j=2:y-2, if(gradDirection(i,j)==90) if (gradDirection(i,j)<(gradDirection(i,j-1) | gradDirection(i,j+1))) gradDirection(i,j)=0; end end if(gradDirection(i,j)==45) if (gradDirection(i,j)<(gradDirection(i+1,j-1) | gradDirection(i-1,j+1))) gradDirection(i,j)=0; end end if(gradDirection(i,j)==-45) if (gradDirection(i,j)<(gradDirection(i-1,j-1) | gradDirection(i+1,j+1))) gradDirection(i,j)=0; end end end end 
