Hilditch Algorithm - some minor problems

I have been writing the code for Hilditch's Thinning Algorithm. The procedures are quite simple and straightforward. But let me explain what I am trying to do in general.

1. Open the image file

2. Convert to BW (Black = 0; White = 1)

3. Add extra rows and columns around the image (to prevent "Index out of bound" error while scanning through the image)

4. If all of the following conditions are met, the pixel will be deleted http://cgm.cs.mcgill.ca/~godfried/teaching/projects97/azar/skeleton.html The link tells everything.

The code:

clc
clear all

imdir='C:\Users\bryan\Desktop\matlab - skeletonization\';
imfile=['apple.jpg'];%num2str(Imagefile,'%05d')
I=imread([imdir,imfile]); 

% Convert to BW by setting threshold (black = 0; white = 1)
I=im2bw(I,0.4); %range = 0-1

[row, col, depth] = size(I);
thinning = 1;
eraceCount = 0;

% add rows to image
addrow = ones(1, col);
I = [addrow; addrow; I; addrow];
[row, col, depth] = size(I);

% add columns to image
addcol = ones(row, 1);
I = horzcat(addcol, I, addcol, addcol);
[row, col, depth] = size(I);

eracePixel(row,col) = 0;

%start thinning
while thinning == 1
    for r = 3:row-1
        for c = 2:col-2
            condition1 = 0;
            condition2 = 0;
            condition3 = 0;
            condition4 = 0;

              if I(r,c) == 0; %black pixel found
                  %for condition 1
                  B = 0;
                  B = I(r-1,c) + I(r-1,c+1) + I(r,c+1) +I(r+1,c+1) + I(r+1,c) + I(r+1,c-1) + I(r,c-1) + I(r-1,c-1);
                  if B>=2 && B<=6
                      condition1 = 1;
                      B = 0;
                  end

                  %for condition 2
                  A = 0;
                  if I(r-1,c) == 0 && I(r-1,c-1) == 1
                      A = A + 1;
                  end
                  if I(r-1,c+1) == 0 && I(r-1,c) == 1
                      A = A + 1;
                  end
                  if I(r,c+1) == 0 && I(r-1,c+1) == 1
                      A = A + 1;
                  end
                  if I(r+1,c+1) == 0 && I(r,c+1) == 1
                      A = A + 1;
                  end
                  if I(r+1,c) == 0 && I(r+1,c+1) == 1
                      A = A + 1;
                  end
                  if I(r+1,c-1) == 0 && I(r+1,c) == 1
                      A = A + 1;
                  end
                  if I(r,c-1) == 0 && I(r+1,c-1) == 1
                      A = A + 1;
                  end
                  if I(r-1,c-1) == 0 && I(r,c-1) == 1
                      A = A + 1;
                  end

                  if A == 1
                      condition2 = 1;
                      A = 0;
                  end

                  %for condition 3
                  if I(r-1,c) == 1 && I(r,c+1) == 1 && I(r,c-1) == 1
                      condition3 = 1;
                  end

                      %A(p2) =!1 (condition 3)
                  A2 = 0;
                  if I(r-2,c) == 0 && I(r-2,c-1) == 1
                      A2 = A2 + 1;
                  end
                  if I(r-2,c+1) == 0 && I(r-2,c) == 1
                      A2 = A2 + 1;
                  end
                  if I(r-1,c+1) == 0 && I(r-2,c+1) == 1
                      A2 = A2 + 1;
                  end
                  if I(r,c+1) == 0 && I(r-1,c+1) == 1
                      A2 = A2 + 1;
                  end
                  if I(r,c) == 0 && I(r,c+1) == 1
                      A2 = A2 + 1;
                  end
                  if I(r,c-1) == 0 && I(r,c) == 1
                      A2 = A2 + 1;
                  end
                  if I(r-1,c-1) == 0 && I(r,c-1) == 1
                      A2 = A2 + 1;
                  end
                  if I(r-2,c-1) == 0 && I(r-1,c-1) == 1
                      A2 = A2 + 1;
                  end

                  if A2 ~= 1
                      condition3 = 1;
                  end 

                  %for condition 4
                  if I(r-1,c) == 1 && I(r,c+1) == 1 && I(r+1,c) == 1
                      condition4 = 1;
                  end

                      %A(p4) =!1 (condition 4)
                  A4 = 0;
                  if I(r-1,c+1) == 0 && I(r-1,c) == 1
                      A4 = A4 + 1;
                  end
                  if I(r-1,c+2) == 0 && I(r-1,c+1) == 1
                      A4 = A4 + 1;
                  end
                  if I(r,c+2) == 0 && I(r-1,c+2) == 1
                      A4 = A4 + 1;
                  end
                  if I(r+1,c+2) == 0 && I(r,c+2) == 1
                      A4 = A4 + 1;
                  end
                  if I(r+1,c+1) == 0 && I(r+1,c+2) == 1
                      A4 = A4 + 1;
                  end
                  if I(r+1,c) == 0 && I(r+1,c+1) == 1
                      A4 = A4 + 1;
                  end
                  if I(r,c) == 0 && I(r+1,c) == 1
                      A4 = A4 + 1;
                  end
                  if I(r-1,c) == 0 && I(r,c) == 1
                      A4 = A4 + 1;
                  end

                  if A4 ~= 1
                      condition4 = 1;
                  end

                  %marked as to be eraced
                  if condition1 + condition2 + condition3 + condition4 == 4
                      eracePixel(r,c) = 1;
                      eraceCount = eraceCount + 1;
                  end
              end
          end
      end

      if eracePixel == 0;
          thinning = 0;
      end

      I = I + eracePixel;

      %clear all values in matrix eracePixel 
      eracePixel = zeros(row, col);
  end

imshow(I);

/////////////////end of code//////////////////////////////////////////

This is the image that I used for testing

It might be some silly mistakes inside. I hope someone can help me out while I am still looking for improvements. Thank you.