MATLAB: Calculation of pixel shift

Question

Hi,

I have a slated edge image and I want to know the value of required pixel shift to make it vertical. I know the pixel value at first and end point of the edge. But want to scan the image line by line and know the values of shifted pixels for each line. But I am getting an error: *Matrix dimensions must agree for the following line: dif = abs(bw(i:j)- bw(i:j+1))

close all;
clear all;
clc;
I=imread('C:\Users\swati\OneDrive\Documents\MATLAB\Examples\Cropped Image.jpg');
figure;
imshow(I); title('Original Image');
impixelinfo;
m=167;n=200;
%Averaging The Pixels
h=ones(10,10)/100; %Create a normalized pixel; averaging filter.
I_avg=imfilter(I,h); %apply filter to image 
figure(); imshow(I_avg);
title(I_avg);
impixelinfo;
%Scanning of Image
v=I_avg(1,:); %scanning the I_avg Intensity
figure;plot(v);
%converting GrayScale image to Binary Image
for x=1:200
    for y=1:m
        if I_avg(x,y)>mean(I_avg(:))
            bw(x,y)=1;
        elseif I_avg(x,y)<mean(I_avg(:))
            bw(x,y)=0;
        end
    end
end
figure; imshow(bw);
impixelinfo;
%finding first left most pixel when intensity drops to zero in first row
fisrt_value=zeros([1,m]);
fist_value=bw(1,:)
%finding first left most pixel when intensity drops to zero in last row
second_value=zeros([1,m]);
last_value=bw(200,:)
p2x=1;
p2y=56;
p1x=200;
p1y=73;
m=(p2y-p1y)/(p2x-p1x) %find the slope
theta=atand(m)
shifted_pixel=p1y-p2y  % number of shifted pixels
 j=55;
for i = 1:20:200
 dif = abs(bw(i:j)- bw(i:j+1))
 fprintf('Row Number=%0.0f',i);
 pos=find(dif==1)
 shift=p1y-pos 
 j=j+1;
 i= i+1;
end

Could anyone please suggest me what is wrong in my code or is there any other way to do that?

Thanks, Swati

Answer 1

Swati, get rid of all the programming you did for this and replace it with this:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format short g;
format compact;
fontSize = 25;
%===============================================================================

% Get the name of the image the user wants to use.
baseFileName = 'binary.jpg';
% Get the full filename, with path prepended.
folder = []; % Determine where demo folder is (works with all versions).
fullFileName = fullfile(folder, baseFileName);
%===============================================================================
% Read in a demo image.
grayImage = imread(fullFileName);
% Get the dimensions of the image.
% numberOfColorChannels should be = 1 for a gray scale image, and 3 for an RGB color image.
[rows, columns, numberOfColorChannels] = size(grayImage)
if numberOfColorChannels > 1
  % It's not really gray scale like we expected - it's color.
  % Use weighted sum of ALL channels to create a gray scale image.
  grayImage = rgb2gray(grayImage);
  % ALTERNATE METHOD: Convert it to gray scale by taking only the green channel,
  % which in a typical snapshot will be the least noisy channel.
  % grayImage = grayImage(:, :, 2); % Take green channel.
end
% Display the image.


subplot(2, 2, 1);
imshow(grayImage, []);
axis on;
axis image;
caption = sprintf('Original Gray Scale Image');
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo();
% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0, 0, 1, 1]);
% Get rid of tool bar and pulldown menus that are along top of figure.
% set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off')
drawnow;
% Create binary image from grayscale image.
binaryImage = grayImage > 128;
% Display the image.
subplot(2, 1, 1);
imshow(binaryImage, []);
axis on;
axis image;
title('Binary Image', 'FontSize', fontSize, 'Interpreter', 'None');
% Find edge between row 10 and 190
for row = 10:190
  x(row-9) = find(binaryImage(row, :), 1, 'last');
  y(row-9) = row;
end
coefficients = polyfit(x, y, 1);
angle = atand(coefficients(1))
% Rotate the image
rotatedImage = imrotate(binaryImage, angle-90);
% Display the image.
subplot(2, 1, 2);
imshow(rotatedImage, []);
axis on;
axis image;
title('Rotated Image', 'FontSize', fontSize, 'Interpreter', 'None');