How do I extract size (in terms of pixels) from an image? (2024)

Do you need the size of every individual hole and wire, or just some typical (e.g. mean) size? Do you need this to be automated for many images, or just this one?

You may run into problems making a robust automated solution for the "every hole" case unless you can come up with a good way to identify the debris.

I need it for every hole and wire, though I am able to omit certain parts of the image if they are problematic. I need it to work for various images. The user should be able to input their image and I want to eventually be able to provide analysis for whether the hole and wire sizes fulfill certain certification standards.

% Demo by Image Analyst

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;

markerSize = 40;

%--------------------------------------------------------------------------------------------------------

% READ IN IMAGE

fileName = 'grid.PNG';

grayImage = imread(fileName);

% 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.

% Extract the blue channel (so the magenta lines will be white).

grayImage = grayImage(:, :, 3);

end

%--------------------------------------------------------------------------------------------------------

% Display the image.

subplot(2, 2, 1);

imshow(grayImage, []);

impixelinfo;

axis('on', 'image');

title('Original Gray Scale Image', 'FontSize', fontSize, 'Interpreter', 'None');

hold on

drawnow;

% Maximize window.

g = gcf;

g.WindowState = 'maximized'

drawnow;

subplot(2, 2, 2);

imhist(grayImage);

grid on;

low = 133;

high = 255;

% Interactively/visually select the threshold

% https://www.mathworks.com/matlabcentral/fileexchange/29372-thresholding-an-image?s_tid=srchtitle

% [low, high] = threshold(low, high, grayImage)

mask = grayImage > low;

% Fill holes.

mask = imfill(mask, 'holes');

% Display the image.

subplot(2, 2, 3);

imshow(mask, []);

impixelinfo;

axis('on', 'image');

title('Mask Image', 'FontSize', fontSize, 'Interpreter', 'None');

hold on

drawnow;

% Label each blob with 8-connectivity, so we can make measurements of it

[labeledImage, numberOfBlobs] = bwlabel(mask, 8);

% Apply a variety of pseudo-colors to the regions.

coloredLabelsImage = label2rgb (labeledImage, 'hsv', 'k', 'shuffle');

% Display the pseudo-colored image.

% Display the image.

subplot(2, 2, 4);

imshow(coloredLabelsImage);

impixelinfo;

axis('on', 'image');

title('Mask Image', 'FontSize', fontSize, 'Interpreter', 'None');

hold on

drawnow;

% Get all the blob properties. Can only pass in originalImage in version R2008a and later.

props = regionprops(labeledImage, grayImage, 'Area');

numberOfBlobs = size(props, 1);

% Get a list of all the areas

allAreas = [props.Area];

% Compute the mean area.

meanArea = mean(allAreas)

% Show the histogram.

figure

histogram(allAreas);

grid on;

xline(meanArea, 'Color', 'r', 'LineWidth', 3)

caption = sprintf('Distribution of %d Areas. Mean Area = %.2f pixels.', numberOfBlobs, meanArea)

title(caption, 'FontSize', fontSize, 'Interpreter', 'None');

xlabel('Area', 'FontSize', fontSize, 'Interpreter', 'None');

ylabel('Count', 'FontSize', fontSize, 'Interpreter', 'None');

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