How to overlap two histograms , one generated from reference image other for noisy image ?

Actual Program which I tried is,

Prog 1: A = imread('frame2.bmp'); I = rgb2gray(A); J = imnoise(I,'salt & pepper',0.2); figure; imshow(I);title('original image'); figure; imshow(J);title('image with salt&pepper noise=0.2'); figure; imhist(I);title('histogram of refrece image'); figure; imhist(J);title('histogram of salt&pepper noisy image'); figure; K=imhist(I)+imhist(J); hist(K); But didn't get desired output.

[Preethi H L]

My sincere thanks to Image Analyst for the answer with an illustration. Thank you very much

[Image Analyst]

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Answer 1

[Image Analyst]

Do you have R2015b? You can overlap histograms with histogram() - just look at the example in the help:

x = randn(2000,1);
y = 1 + randn(5000,1);
h1 = histogram(x);
hold on
h2 = histogram(y);

[Thorsten]

If you have an older Matlab version without the histogram function, you can use

 h1 = hist(x); plot(h1)
 hold on
 h2 = hist(y); plot(h2)

[Preethi H L]

I have old version of Matlab and I tried the second code but its showing an error i.e "??? Error using ==> mtimes Integers can only be combined with integers of the same class, or scalar doubles.

Error in ==> hist at 78 xx = miny + binwidth*(0:x); " The program on which i tried is, A = imread('frame2.bmp'); I = rgb2gray(A); M=0; V=0.01; J = imnoise(I,'gaussian',M,V); J=im2double(J); figure; imshow(I);title('original image'); figure; imshow(J);title('image with gaussian noise v=0.01'); figure; %imhist(I);title('histogram of refrece image'); h1 = hist(I); plot(h1) hold on h2 = hist(J); plot(h2);title('histogram of image with gauss noise v=0.01');

I have also attached image which I have used.

[Image Analyst]

Try imhist instead of hist:

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;

rgbImage = imread('peppers.png');
subplot(2,2,1);
imshow(rgbImage);
title('Original RGB Image', 'fontSize', fontSize);

grayImage = rgb2gray(rgbImage);
subplot(2,2,2);
imshow(grayImage);
title('Original Gray Scale Image', 'fontSize', fontSize);

% 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') 

M=0;
V=0.01;
noisyImage = imnoise(grayImage,'gaussian',M,V);
noisyImage=im2double(noisyImage);
subplot(2,2,3);
imshow(noisyImage);
title('image with gaussian noise v=0.01', 'fontSize', fontSize);
subplot(2,2,4);
%imhist(I);title('histogram of refrece image');
 h1 = imhist(grayImage);
 plot(h1)
 hold on
 h2 = imhist(noisyImage); 
 plot(h2);
 title('histogram of image with gauss noise v=0.01', 'fontSize', fontSize);
 grid on;