MATLAB: Draw 1 inch Square on Image

imageimage analysisimage processingimage segmentationMATLAB

Hello,

How can I draw 1 inch square on my image and wanted to find number of grains present in that square ? Attached is my Image for reference. In attached RefImage_WithSquare, wanted to count no. of grains present in that square grains on boundary line must be considered as partial grain. Just as we consider in ASTM Grain Analysis.

Best Answer

If your resolution is 96 dpi, use the rectangle() function with a width and height of 96:

imshow('untitled.png');
axis on;
hold on;
impixelinfo(); % Show x, y, RGB as you mouse around over image.
xLeft = 85; % Wherever you want.
yTop = 32;
rectangle('Position', [xLeft, yTop, 96, 96], 'EdgeColor', 'r', 'LineWidth', 2);

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MATLAB: How to reduce blob using aspect ratio

Dominic, here is the full demo:

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 = 25;
%===============================================================================

% Get the name of the image the user wants to use.
baseFileName = '4.png';
% 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, 1, 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;
% Threshold the image.
binaryImage = grayImage > 128;
% Find connected components (blobs).
labeledImage = bwlabel(binaryImage);
% Make the measurements of the bounding boxes.
props = regionprops(labeledImage, 'BoundingBox');
bb = [props.BoundingBox];
allWidths = bb(3:4:end)
allHeights = bb(4:4:end)
aspectRatio = [allWidths./allHeights ;  allHeights  ./ allWidths]
aspectRatios = max(aspectRatio, [], 1)
compactIndexes = find(aspectRatios > 1.5) % or whatever.
% Extract only those blobs with high aspect ratios.
binaryImage = ismember(labeledImage, compactIndexes);
% Display the image.
subplot(2, 1, 2);
imshow(binaryImage, []);
axis on;
axis image;
caption = sprintf('Final binary image with only high aspect ratio blobs');
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');

MATLAB: What does the below line illustrate in finding bounding box coordinates

The form for the bounding box is [xLeft, yTop, width, height].

So to get the x on the right, you do

xRight = xLeft + width;

To get the y on the bottom row, you do

yBottom = yTop + height;

Knowing that you can get the (x,y) coordinates of any corner in the box.

Best Answer

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MATLAB: How to reduce blob using aspect ratio

MATLAB: What does the below line illustrate in finding bounding box coordinates

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