I examine a grayscale image by dividing it to 50x50 as parts(windows), each part has 3 types of color. I found the avrg of the background type only and need to set dark pixls to this avrg and set other to white. I couldnt fix the errors? Need help.

clear all;
clc;
close all;

ImageinRGB = imread('\DSCF0074new3.tif');

I = rgb2gray(ImageinRGB);
figure, imshow(I), title('Grayscale');

A=double(I);
[r c]=size(A);
count = 0;
sumofBacgrounds = 0;
AvgofBackgrounds = 0;

for column = 1: c 
    checkCol = c - column;
    if (checkCol > 50 | checkCol == 50)
        for row = 1: r 
            checkRow = r - row;
                    if(checkRow > 50 | checkRow == 50)
                        TestWindow = I(row:row+49,column:column+49);
                        for colofWindow = 1: length(TestWindow)
                            for rowofWindow = 1: size(TestWindow,1)
                                    if (I(rowofWindow,colofWindow)<95 & I(rowofWindow,colofWindow)>58)
                                               count = count+1;
                                               sumofBacgrounds =sumofBacgrounds + I(rowofWindow,colofWindow);
                                               AvgofBackgrounds = sumofBacgrounds / count;
                                    end
                            end
                        end

                          for colofWindow = 1: length(TestWindow)
                              for rowofWindow = 1: size(TestWindow,1)
                                       if (I(rowofWindow,colofWindow)<58)
                                                 I(rowofWindow,colofWindow) = AvgofBackgrounds;
                                      elseif (I(rowofWindow,colofWindow)>95)
                                                 I(rowofWindow,colofWindow) = 255;
                                      end
                              end
                          end
                          sumofBacgrounds = 0;
                          AvgofBackgrounds = 0; 

                      else
                          TestWindow = I(row:row+checkRow,column:column+49);
                          for colofWindow = 1: length(TestWindow)
                              for rowofWindow = 1: size(TestWindow,1)
                                   if (I(rowofWindow,colofWindow)<95 & I(rowofWindow,colofWindow)>58)
                                                 count = count+1;
                                                 sumofBacgrounds =sumofBacgrounds + I(rowofWindow,colofWindow);
                                                 AvgofBackgrounds = sumofBacgrounds / count;
                                   end 
                              end
                          end  
                              for colofWindow = 1: length(TestWindow)
                                  for rowofWindow = 1: size(TestWindow,1)
                                       if (I(rowofWindow,colofWindow)<58)
                                                 I(rowofWindow,colofWindow) = AvgofBackgrounds;
                                        elseif (I(rowofWindow,colofWindow)>95)
                                                 I(rowofWindow,colofWindow) = 255;
                                       end
                                  end
                               end
                      end
                    sumofBacgrounds = 0;
                    AvgofBackgrounds = 0; 
           end

      else
         for row = 1: r 
             checkRow = r - row;
                      if(checkRow > 50 | checkRow == 50)
                          TestWindow = I(row:row+49,column:column+checkCol);
                          for colofWindow = 1: length(TestWindow)
                              for rowofWindow = 1: size(TestWindow,1)
                                       if (I(rowofWindow,colofWindow)<95 & I(rowofWindow,colofWindow)>58)
                                                 count = count+1;
                                                 sumofBacgrounds =sumofBacgrounds + I(rowofWindow,colofWindow);
                                                 AvgofBackgrounds = sumofBacgrounds / count;
                                       end
                              end
                          end    
                           for colofWindow = 1: length(TestWindow)
                              for rowofWindow = 1: size(TestWindow,1)
                                       if (I(rowofWindow,colofWindow)<58)
                                                 I(rowofWindow,colofWindow) = AvgofBackgrounds;
                                      elseif (I(rowofWindow,colofWindow)>95)
                                                 I(rowofWindow,colofWindow) = 255;
                                      end
                              end
                           end

                          sumofBacgrounds = 0;
                          AvgofBackgrounds = 0; 
                      else
                          TestWindow = I(row:row+checkRow,column:column+checkCol);
                          for colofWindow = 1: length(TestWindow)
                              for rowofWindow = 1: size(TestWindow,1)
                                   if (I(rowofWindow,colofWindow)<95 & I(rowofWindow,colofWindow)>58)
                                                 count = count+1;
                                                 sumofBacgrounds =sumofBacgrounds + I(rowofWindow,colofWindow);
                                                 AvgofBackgrounds = sumofBacgrounds / count;
                                   end 
                              end
                          end  

                         for colofWindow = 1: length(TestWindow)
                                  for rowofWindow = 1: size(TestWindow,1)
                                       if (I(rowofWindow,colofWindow)<58)
                                                 I(rowofWindow,colofWindow) = AvgofBackgrounds;
                                        elseif (I(rowofWindow,colofWindow)>95)
                                                 I(rowofWindow,colofWindow) = 255;
                                       end
                                  end
                         end
                          sumofBacgrounds = 0;
                          AvgofBackgrounds = 0; 
                      end    

          end 

      end

end

figure, imshow(I), title('GrayscalePartAfterAdjust');

Answer 1

[Walter Roberson]

Change your lines

                                                 sumofBacgrounds =sumofBacgrounds + I(rowofWindow,colofWindow);

to

                                                 sumofBacgrounds = sumofBacgrounds + double(I(rowofWindow,colofWindow));

[Ahmad Yahya]

Thanks sir Roberson. It did good, but it stopped at at the first part and did not move to the rest of the parts. If u can help, please, thanks?

[Walter Roberson]

I would suggest that you completely rewrite your code to use logical indexing. blockproc() to have your algorithm run on 50 by 50 blocks. For each block,

mask_low = block.data <= 58;
mask_high = block.data >= 95;
mask_background = ~mask_low & ~mask_high;
avgofBackgrounds = mean( double( block.data(mask_background) );
block.data(mask_low) = avgofBackgrounds;
block.data(mask_high) = 255;

[Image Analyst]

Put that code into nlfilter(). I'm attaching a demo of nlfilter.