How to draw multiple lines on a image and calculate the all length for multiple image?
How to draw multiple lines on a image and calculate the all length for multiple image?
Neeta Dsouza answered .
2025-11-20
Try this:
clc; % Clear the command window.
clear all;
close all; % Close all figures (except those of imtool.)
workspace; % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 16;
%===============================================================================
% Get the name of the image the user wants to use.
baseFileName = 'rnfl.webp';
folder = pwd;
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
% The file doesn't exist -- didn't find it there in that folder.
% Check the entire search path (other folders) for the file by stripping off the folder.
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
%=======================================================================================
% Read in demo image.
grayImage = imread(fullFileName);
% Get the dimensions of the image.
[rows, columns, numberOfColorChannels] = size(grayImage)
if numberOfColorChannels > 1
grayImage = rgb2gray(grayImage);
end
% Display image.
subplot(2, 2, 1);
imshow(grayImage, []);
impixelinfo;
axis on;
caption = sprintf('Original Image\n%s', baseFileName);
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.
% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0.05 1 0.95]);
% 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;
% Ask user to draw a line across the image.
message = sprintf('Draw the baseline across the gap.\nLeft click the left point.\nRight click the right point.');
text(5, 250, message, 'Color', 'r', 'FontSize', 16);
uiwait(msgbox(message));
[cx, cy, mask] = improfile();
hold on;
plot(cx, cy, 'r-', 'LineWidth', 2);
%===================================================================================
% Get a histogram
subplot(2, 2, 2);
imhist(grayImage);
grid on;
title('Histogram of gray scale image', 'FontSize', fontSize, 'Interpreter', 'None');
% Convert to binary
binaryImage = grayImage > 29;
% Display image.
subplot(2, 2, 3);
imshow(binaryImage, []);
impixelinfo;
axis on;
title('Binary Image', 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
% Take the 2 largest blobs.
binaryImage = bwareafilt(binaryImage, 2);
% % fill any small holes in lines (not sure if needed)
% binaryImage = imfill(binaryImage,'holes');
% Display image.
subplot(2, 2, 3);
imshow(binaryImage, []);
impixelinfo;
axis on;
title('Binary Image', 'FontSize', fontSize, 'Interpreter', 'None');
% Draw line across binary image also.
hold on;
plot(cx, cy, 'r-', 'LineWidth', 2);
% For every cx, find the delta Y between cy and the top-most white pixel of the binary image.
deltaY = zeros(1, columns);
hold on;
for k = 1 : length(cx)
thisX = round(cx(k));
thisY = round(cy(k));
% Extract column of binaryImage.
thisColumn = binaryImage(:, thisX);
topLineOfBinaryImage = find(thisColumn, 1, 'first');
% Skip it if it's above the red line they drew.
if topLineOfBinaryImage < thisY
continue;
end
deltaY(thisX) = topLineOfBinaryImage - thisY;
if rem(thisX, 5) == 0
% Make blue line every 5 columns. We still have deltaY for every column though.
line([thisX, thisX], [thisY, topLineOfBinaryImage], 'Color', 'c');
end
end
% Get the mean height.
meanHeight = mean(deltaY(deltaY>0))
% Display plot.
subplot(2, 2, 4);
plot(deltaY, 'b-', 'LineWidth', 2);
grid on;
message = sprintf('Delta Y vs. Column. The mean height = %f', meanHeight);
title(message, 'FontSize', fontSize, 'Interpreter', 'None');
xlabel('Column', 'FontSize', fontSize, 'Interpreter', 'None');
ylabel('Delta Y', 'FontSize', fontSize, 'Interpreter', 'None');
% Draw a line across the plot at the mean height.
hold on;
line(xlim, [meanHeight, meanHeight], 'color', 'r', 'LineWidth', 2);
message = sprintf('The mean height = %f', meanHeight);
uiwait(helpdlg(message));