Histograms of Oriented Gradient

Hi all I have applied HOG into a video sequence without SVM classifier.But I am not getting any result.my code is here.

clc;

   close all;
    source='campus_raw.AVI';
    vidobj=videoreader(source);
   Height=vidobj.Height;
    Width=vidobj.width;
     frames=vidobj.NumberOfFrames;
      threshold=10;  
      nbins=9;    
  for f=1:frames    
  thisframe=read(vidobj,f);
   figure(1);imshow(thisframe);
  [Rows Cols Colors]=size(thisframe);
  nwin_x=3;
  nwin_y=3;
  H=zeros(nwin_x*nwin_y*nbins);
  m=sqrt(Rows/2);
  step_x=floor(m/(nwin_x+1));
  step_y=floor(m/(nwin_y+1));
  cont=0;
  % Gamma/Color Normalization..

if Colors>1    
GrayImage=rgb2gray(thisframe);
GrayImage=double(GrayImage);
else
    GrayImage=thisframe;
end
% Gradient Computation
Gx=[-1 0 1];
Gy=-Gx;
Grad_ImageX=imfilter(double(GrayImage),Gx);
Grad_ImageY=imfilter(double(GrayImage),Gy);
MagImage=((Grad_ImageX.^2)+(Grad_ImageY)).^0.5;
%figure(3);imshow(MagImage);
DirImage=atan2(Grad_ImageY,Grad_ImageX);
%figure(4);imshow(DirImage);
nbins=9;

for n=0:nwin_y-1
    for m=0:nwin_x-1
cont=cont+1;
DirImage1=DirImage(n*step_y+1:(n+2)*step_y,m*step_x+1:(m+2)*step_x);
MagImage1=MagImage(n*step_y+1:(n+2)*step_y,m*step_x+1:(m+2)*step_x);
 v_angles=DirImage1(:);    
        v_magnit=MagImage1(:);

   K=max(size(v_angles));
  B=0;
  Hist=zeros(nbins,1);
   for ang_lim=-pi+2*pi/nbins:2*pi/nbins:pi;
   B=B+1;
   for k=1:K
         if v_angles(k)<ang_lim
                      v_angles(k)=100;
                      Hist(B)=Hist(B)+v_magnit(k);
         end

   end
   end
   Hist=Hist/(norm(Hist)+0.01);        
   H((cont-1)*nbins+1:cont*nbins,1)=Hist;

      end
      figure(3);imshow(Hist(B));

end 

   end

figure(3);imshow(Hist(B)) shows nothing to me.Why?Any help please.

Thanks .

Answer 1

[Walter Roberson]

You are using B as a counter, and Hist is a vector, so Hist(B) would be a single element out of the vector. You then try to show that single element as if it were an entire image. If you are sure that is what you want, then what you probably need to do is change your imshow(Hist(B)) to imshow(Hist(B),[])

[Walter Roberson]

Please put a breakpoint in at the line

Hist(B)=Hist(B)+v_magnit(k);

and verify that you do reach that sometimes, and that the v_magnit(k) is non-zero.

Also, please go back through your code and indent it consistently. e.g., currently your "cont=cont+1;" line is indented at the same level as "for m". It is a strain to debug someone else's code when the indentation is inconsistent.