How to find the co-ordinates in an image?

In the attached image,how do i find the co-ordinates of first letter(i.e. starting balck pixel of 'a') and co-ordinates of last letter?(i.e.last pixel of letter 'e') Please help me Thank you

Answer 1

[Image Analyst]

Try 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 long g;
format compact;
fontSize = 20;

% Check that user has the Image Processing Toolbox installed.
hasIPT = license('test', 'image_toolbox');
if ~hasIPT
  % User does not have the toolbox installed.
  message = sprintf('Sorry, but you do not seem to have the Image Processing Toolbox.\nDo you want to try to continue anyway?');
  reply = questdlg(message, 'Toolbox missing', 'Yes', 'No', 'Yes');
  if strcmpi(reply, 'No')
    % User said No, so exit.
    return;
  end
end

%===============================================================================
% Read in a standard MATLAB gray scale demo image.
folder = pwd;
baseFileName = 'oneline.png';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
  % File doesn't exist -- didn't find it there.  Check the search path for it.
  fullFileNameOnSearchPath = baseFileName; % No path this time.
  if ~exist(fullFileNameOnSearchPath, 'file')
    % Still didn't find it.  Alert user.
    errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
    uiwait(warndlg(errorMessage));
    return;
  end
end
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, []);
axis on;
title('Original Grayscale Image', 'FontSize', fontSize, 'Interpreter', 'None');

% 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')

% Let's compute and display the histogram.
[pixelCount, grayLevels] = imhist(grayImage);
subplot(2, 2, 2);
bar(grayLevels, pixelCount); % Plot it as a bar chart.
grid on;
title('Histogram of original image', 'FontSize', fontSize, 'Interpreter', 'None');
xlabel('Gray Level', 'FontSize', fontSize);
ylabel('Pixel Count', 'FontSize', fontSize);
xlim([0 grayLevels(end)]); % Scale x axis manually.

% Get a horizontal profile
horizontalProfile = sum(grayImage, 1) / rows;

% Threshold the image and create a binary image
subplot(2, 2, 3);
x = 1:length(horizontalProfile);
plot(x, horizontalProfile, 'b-', 'LineWidth', 2); % Plot it as a line.
grid on;
title('Profile of original image', 'FontSize', fontSize, 'Interpreter', 'None');
xlabel('Column Number', 'FontSize', fontSize);
ylabel('Gray Level', 'FontSize', fontSize);

% Threshold at 240
theThreshold = 240;
inAWord = find(horizontalProfile < theThreshold)
% Draw a red line over the plot
hold on;
plot([x(1), x(end)], [theThreshold, theThreshold], 'r-', 'LineWidth', 2); % Plot it as a line.

% Determine the left and right-most columns:
leftColumn = inAWord(1);
rightColumn = inAWord(end);

% Display the original gray scale image.
subplot(2, 2, 4);
imshow(grayImage, []);
axis on;
title('Image with detected words', 'FontSize', fontSize, 'Interpreter', 'None');

% Put up shaded areas over words
hold on;
for k = 1 : length(inAWord)
  col = inAWord(k);
  fill([col, col], [1, rows], 'y', 'FaceAlpha', 0.1, 'EdgeColor', 'y');
end

message = sprintf('The left column = %d\nThe right column = %d', leftColumn, rightColumn);
uiwait(helpdlg(message));

[sindhu c]

It worked! Thanks a lot

[sindhu c]

so is it (1,230) and (1690,250) are the co-ordinates of first and last letter resp?

[Poornima Gokhale]

hello sir. I tried the above code given by you to get the co-ordinates. But where are the co-ordinates?means I want it in the form of (x,y)

[Image Analyst]

y doesn't really apply since the input was already one line that had been extracted. So y1 = 1, and y2 = number of rows in the image.

For x, that's the column number and those are in the array called "inAWord."

[Meghashree G]

sir,i tried yo code.do u mean that y1=1 and y2 = 1690 .. and the array contains column 1 through 1334..how can i get the value of x1 and x2??

[Image Analyst]

No, from what I can see on the left hand side axes, the y1 was 1 and the y2 was about 110 or so.

And there are lots of x1 and x2, right? There is a pair of starting and stopping x for every "word". The inAWord array has an index for every x location that is in a word. If you want the starting and stopping x, you'd have to use something like diff() to get just those points. Something like (untested):

logicalIndexes = horizontalProfile < theThreshold
startingX = 1 + find(diff(logicalIndexes) > 0);
endingX = 1 + find(diff(logicalIndexes) < 0);

[Meghashree G]

sir,when i inserted those lines which u gave its displaying logicalIndexes values columns from through through 1703.but not getting anything when tried to display endingX

[Image Analyst]

What is endingX? Maybe later today I can download the image and code and try it for you. No guarantees though.

[Meghashree G]

endingX = 1 + find(diff(logicalIndexes) < 0); This one which you gave,...And i would be grateful for that.Please do try when you are free