MATLAB Answers


how i can get image_intensity and var from image?

Asked by Faisah
on 25 May 2013

can anyone give me example about adding noise localvar to image?

in this program,

J = imnoise(I,'localvar',image_intensity,var)

you can see there is image_intensity and variance, how i can get that?


  1 Comment

They're basically a look up table that says how much noise each intensity gets. You can use an equation if you want.

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1 Answer

Answer by Image Analyst
on 25 May 2013

See my demo:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures if you have the Image Processing Toolbox.
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.
% Read in a standard MATLAB gray scale demo image.
folder = fullfile(matlabroot, '\toolbox\images\imdemos');
button = menu('Use which demo image?', 'CameraMan', 'Moon', 'Eight', 'Coins', 'Pout');
if button == 1
	baseFileName = 'cameraman.tif';
elseif button == 2
	baseFileName = 'moon.tif';
elseif button == 3
	baseFileName = 'eight.tif';
elseif button == 4
	baseFileName = 'coins.png';
	baseFileName = 'pout.tif';
% Read in a standard MATLAB gray scale demo image.
folder = fullfile(matlabroot, '\toolbox\images\imdemos');
% 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.
	fullFileName = baseFileName; % No path this time.
	if ~exist(fullFileName, 'file')
		% Still didn't find it.  Alert user.
		errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
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.
% Display the original gray scale image.
subplot(1, 2, 1);
imshow(grayImage, []);
title('Original Grayscale Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
% Give a name to the title bar.
set(gcf,'name','Demo by ImageAnalyst','numbertitle','off') 
% Make up a relationship between the gray level of the noise and the variance.
image_intensity = [0:255]/255;
varAmplitude = linspace(0, 0.01, 256);
noisyImage = imnoise(im2double(grayImage),'localvar',image_intensity,varAmplitude);
% Display the original gray scale image.
subplot(1, 2, 2);
imshow(noisyImage, []);
title('Noisy Image', 'FontSize', fontSize);


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