Please help me in OMR

pic = dir('C:\Users\USER\Desktop\MMW\BSBA-01\*.jpg');

for a=1:length(pic);
    filename = strcat('C:\Users\USER\Desktop\MMW\BSBA-01\',pic(a).name);
I=rgb2gray(imread(filename));
options='ABCD'; % Options
ans=''; % This string stores the options entered by the student
key=' D C D C A D B A D B A A D D C A B C C C D A A A D D D A D D A A D A D D A D D A B C B B C C A C A A'; % This string contains correct answers

x=885; % x-coordinate of first bubble
y=770; % y-coordinate of first bubble

s=105; %spacing between each bubble
sr=95; %spacing between consecutive rows

for i=1:25                               
    sy=y+(i-1)*sr;

      for j=1:4          
      sx=x+(j-1)*s;
   %     disp(sx);
   %     disp(sy);

   %    disp(I(sy,sx));
      if((I(sy,sx)<25))        
          c(i,j)=0;
       else
          c(i,j)=1;    
      end

      end
  end

what does the 25 mean in this line?

if((I(sy,sx)<25))

Answer 1

[Walter Roberson]

It looks arbitrary to me. It looks like you are doing optical mark reading, and that that statement is detecting whether a particular location on the card is sufficiently dark to be considered filled in. Dark pixels have low uint8 values.

[Mark Jecel Rapir]

thank you. YEs Im working on OMR.

what does I(sx,sy) give? is it the number of pixel? if so, how can I determine the number of pixels?

[Walter Roberson]

It is not the number of pixels, it is the intensity associated with the pixel located in row given by sx, column given by sy.

This is, by the way, a bit misleading. MATLAB arrays are indexed with y as the first coordinate, x as the second coordinate: the row is considered to be how far up or down you are (corresponding to y) and the column is how far left or right you are (corresponding to x).