MATLAB: How to make a binary image by specifying a threshold? for example more than intensity 200 be 1 and less than be 0

binary imageImage Processing ToolboxMATLAB

how do I make a binary image by specifying a threshold? for example more than intensity 200 be 1 and less than be 0?

Best Answer

Or just

BW = YourImage > 200;

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MATLAB: Threshold

See my demo (simply copy and paste):

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures.
clear;  % Erase all existing variables.
workspace;  % Make sure the workspace panel is showing.
fontSize = 20;
% Change the current folder to the folder of this m-file.
if(~isdeployed)
  cd(fileparts(which(mfilename)));
end
  
% 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 = fullfile(matlabroot, '\toolbox\images\imdemos');
baseFileName = 'cell.tif';
fullFileName = fullfile(folder, baseFileName);
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
if ~exist(fullFileName, 'file')
  % Didn't find it there.  Check the search path for it.
  fullFileName = baseFileName; % No path this time.
  if ~exist(fullFileName, 'file')
    % Still didn't find it.  Alert user.
    errorMessage = sprintf('Error: %s does not exist.', 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);
% Display the original gray scale image.
subplot(2, 2, 1);
imshow(grayImage, []);
title('Original Grayscale Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'Position', get(0,'Screensize')); 
set(gcf,'name','Demo by ImageAnalyst','numbertitle','off') 
% Threshold the image.
binaryImage = grayImage >= 70 & grayImage <= 130;
% Display the binary image.
subplot(2, 2, 2);
imshow(binaryImage, []);
title('Binary Image', 'FontSize', fontSize);
% Mask the image.
maskedImage = grayImage; % Initialize.
maskedImage(~binaryImage) = 0;
% Display the masked image.
subplot(2, 2, 3);
imshow(maskedImage, []);
title('Masked Image', 'FontSize', fontSize);
msgbox('Done with demo!');

MATLAB: Binarize image with threshold

You can use graythresh() and bwthresh() which use 0-1, but I think it's simpler to just do

binaryImage = grayImage < grayLevelThreshold;

where grayLevelThreshold is just the regular threshold (0-255 or 0-65535) rather than anormalized number in the range 0-1.

Best Answer

Related Solutions

MATLAB: Threshold

MATLAB: Binarize image with threshold

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