How do you segment the image horizontally?

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peyush 2015-6-24

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评论： Divya 2017-1-17

Hi guys... I have an image containing a handwritten sentence of four lines... i want to segment the image into 4 segmented parts horizontally, such that each segmented part contain each of the four line... can any one help???... any help is highly appreciated!!!

PS: the image to be segmented is binary image with black background and white handwritten characters on it

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Image Analyst 2015-6-24

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You could try summing the image horizontally:

verticalProfile = sum(binaryImage, 2);

then look for bright and non-bright rows. Or you could use a long horizontal structuring element and do a morphological closing with imclose() and then look for the big blobs.

I'm sure there are published algorithms that are much better that you can find here: http://www.visionbib.com/bibliography/contentschar.html#OCR,%20Document%20Analysis%20and%20Character%20Recognition%20Systems

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peyush 2015-6-26

编辑：peyush 2015-6-26

在 MATLAB Online 中打开

ok thanks...

 %%_summing the image horizontally_
 verticalProfile = sum(binaryImage, 2);
 %%_create logical vector of what lines have text and which do not based on
 %%threshold_
 rowsWithText = verticalProfile > 20;
 %%_finding top and bottom lins_
 topLines = find(diff(rowsWithText) == 1);
 bottomLines = find(diff(rowsWithText) == -1);
 %%_looping for extracting characters in the image_
 for k = 1 : length(topLines)  %%_loop for segmenting horizontal lines_
     topRow = topLines(k);
     bottomRow = bottomLines(k);
     thisLine = binaryImage(topRow:bottomRow, :);
     figure;
     imshow(thisLine, []);
     %%_summing the segmented image vertically_
     horizontalProfile = sum(thisLine, 1);
     columnWithText = horizontalProfile > 0;
     leftCharacter = find(diff(columnWithText) == 1);
     rightCharacter = find(diff(columnWithText) == -1);
     for m = 1 : length(leftCharacter)  %%_loop for segmenting each individual character_
         leftColumn = leftCharacter(m);
         rightColumn = rightCharacter(m);
         thisCharacter = thisLine(leftColumn:rightColumn, :);
         figure;
         imshow(thisCharacter, []);
     end
 end

and, " Index exceeds matrix dimensions " is the only error message it is showing in red

Image Analyst 2015-6-26

编辑：Image Analyst 2015-11-18

在 MATLAB Online 中打开

This is what I was expecting you to give me. Anyway, try it. It appears that your original binary image has a lot of breaks in the characters.

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 long g;
format compact;
fontSize = 20;
tic;
fullFileName = fullfile(pwd, 'SampleImage.png');
grayImage = imread(fullFileName);
% Get the dimensions of the image.
% numberOfColorBands should be = 1.
[rows, columns, numberOfColorBands] = size(grayImage);
if numberOfColorBands > 1
  % It's not really gray scale like we expected - it's color.
  % Convert it to gray scale by taking only the green channel.
  grayImage = grayImage(:, :, 2); % Take green channel.
end
% Display the original gray scale image.
subplot(2, 2, 1);
imshow(grayImage, []);
title('Original Grayscale Image', 'FontSize', fontSize, 'Interpreter', 'None');
axis on;
% 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')
binaryImage = grayImage > 128;
subplot(2, 2, 2);
imshow(binaryImage);
title('Binary Image', 'FontSize', fontSize, 'Interpreter', 'None');
axis on;
% _summing the image horizontally_
verticalProfile = sum(binaryImage, 2);
subplot(2, 2, 3);
plot(verticalProfile, 'b-');
grid on;
% _create logical vector of what lines have text and which do not based on
%threshold_
rowsWithText = verticalProfile > 20;
% _finding top and bottom lins_
topLines = find(diff(rowsWithText) == 1);
bottomLines = find(diff(rowsWithText) == -1);
% _looping for extracting characters in the image_
  for k = 1 : length(topLines)  % _loop for segmenting horizontal lines_
  topRow = topLines(k);
  bottomRow = bottomLines(k);
  thisLine = binaryImage(topRow:bottomRow, :);
  subplot(2, 2, 3);
  imshow(thisLine, []);
  axis on;
  
  % _summing the segmented image vertically_
  horizontalProfile = sum(thisLine, 1);
  plot(horizontalProfile, 'b-');
  grid on;
  columnWithText = horizontalProfile > 2;
  leftCharacter = find(diff(columnWithText) == 1);
  rightCharacter = find(diff(columnWithText) == -1);
  if isempty(leftCharacter) || isempty(rightCharacter)
    continue;
  end
  promptMessage = sprintf('Do you want to find letters within this line,\nor Cancel to abort processing?');
  titleBarCaption = 'Continue?';
  button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Cancel', 'Continue');
  if strcmpi(button, 'Cancel')
    return;
  end
  imshow(thisLine, []);
  axis on;
  subplot(2, 2, 4);
  for m = 1 : length(leftCharacter)  % loop for segmenting each individual character
    leftColumn = leftCharacter(m);
    rightColumn = rightCharacter(m);
    thisCharacter = thisLine(:, leftColumn:rightColumn);
    imshow(thisCharacter, []);
    axis on;
    promptMessage = sprintf('Do you want to find the next letter,\nor Cancel to abort processing?');
    titleBarCaption = 'Continue?';
    button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Cancel', 'Continue');
    if strcmpi(button, 'Cancel')
      return;
    end
  end
end

Meghashree G 2016-1-25

Line_segmentation.m

Hello sir,i have many similar forms like this.But segmentation of lines is not correctly achieved .How to modify the code??Please help me with this.

Walter Roberson 2016-1-25

As Image Analyst already replied,

"Otherwise, look at the link I gave to the papers of people who study this as their main career. I don't do OCR and I'm sure my algorithms just off the top of my head are not as successful as those from someone whose full time job OCR is. Please see their published papers if you want something better."

OCR is not just a trick that you get the hang of, not just a matter of fixing off-by-one errors in indexing, not just a matter of knowing the right threshold to use. OCR takes a lot of work. There are a lot of different techniques with different strengths and weaknesses. You can find several hundred books and proceedings on Amazon.com on the topic. There are a number of different conferences on the topic. You can find over one million articles about optical character recognition on scholar.google.com . It is a hard topic to do well.

Image Analyst does not have time to read and understand all of those on your behalf. And I know that I have no interest in reading and understanding those on your behalf. Very few of the regular volunteers have expressed interest in OCR. When we need OCR, we use someone else's program instead of trying to design our own. For example we might call http://www.mathworks.com/help/vision/ref/ocr.html

Your situation has exceeded our available resources, so is time for you to start doing your research.

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