Unrecognized function or variable 'imnoise2'.

Initially, I need to denoise the image using the Rayleigh function.

I am working on a lab and when I run the command:

% // Generate Uniform Noise Matrices, Scaled Down by 70%.
UN_R =  0.3 * imnoise2('uniform', 512, 512);
UN_G =  0.3 * imnoise2('uniform', 512, 512);
UN_B =  0.3 * imnoise2('uniform', 512, 512);

As instructed I get the error:

Unrecognized function or variable 'imnoise2'.

Error in noise (line 29)
UN_R =  0.3 * imnoise2('uniform', 512, 512);

Here is all the code used:

%....................................................................
% // Uniform Random Noise in The Range [0, 1] Scaled by k =  0.3.   |
% // Rayleigh Noise with its [A = 0, B = 1] Scaled by k = 0.3.      |
% // Exponential Noise Scaled By 0.2 Where The Value of A = 1.      |
% // Gamma (Erlang) Noise where [A, B ] = [2, 5] and SF 'K' = 0.1.  |
% // imnoise2.m File Function Is Called Inside This Program.        |
%...................................................................|
%// Read an Image from The Given Path.
img = imread('airport512x512.bmp');
% // Extract Red, Green and Blue Channels of Input. 
Rframe = img(:, :, 1);
Gframe = img(:, :, 2);
Bframe = img(:, :, 3);
Rframe = double(Rframe);
Gframe = double(Gframe);
Bframe = double(Bframe);
% // Normalized Intensities of Each Channel [0, 1].
Rframe = Rframe - min(Rframe(:));
Rframe = Rframe / max(Rframe(:));
Gframe = Gframe - min(Gframe(:));
Gframe = Gframe / max(Gframe(:));
Bframe = Bframe - min(Bframe(:));
Bframe = Bframe / max(Bframe(:));
% // Generate Uniform Noise Matrices, Scaled Down by 70%.
UN_R =  0.3 * imnoise2('uniform', 512, 512);
UN_G =  0.3 * imnoise2('uniform', 512, 512);
UN_B =  0.3 * imnoise2('uniform', 512, 512);
% // Generate Rayleigh Noise Matrices, Scaled Down by 70%.
RN_R =  0.3 * imnoise2('rayleigh', 512, 512);
RN_G =  0.3 * imnoise2('rayleigh', 512, 512);
RN_B =  0.3 * imnoise2('rayleigh', 512, 512);
% // Generate Exponential Noise Matrices, Scaled Down by 80%.
EN_R =  0.2 * imnoise2('exponential', 512, 512);
EN_G =  0.2 * imnoise2('exponential', 512, 512);
EN_B =  0.2 * imnoise2('exponential', 512, 512);
% // Generate Erlang Noise Matrices, Scaled Down by 90%.
GN_R =  0.1 * imnoise2('erlang', 512, 512);
GN_G =  0.1 * imnoise2('erlang', 512, 512);
GN_B =  0.1 * imnoise2('erlang', 512, 512);
% // Add Uniform Noises to Each Image Channel [R, G, B]. 
R_UNoisy = Rframe + UN_R;
G_UNoisy = Gframe + UN_G;
B_UNoisy = Bframe + UN_B;
% // Add Rayleigh Noises to Each Image Channel [R, G, B]. 
R_RNoisy = Rframe + RN_R;
G_RNoisy = Gframe + RN_G;
B_RNoisy = Bframe + RN_B;
% // Add Exponential Noises to Each Image Channel [R, G, B]. 
R_ENoisy = Rframe + EN_R;
G_ENoisy = Gframe + EN_G;
B_ENoisy = Bframe + EN_B;
% // Add Gamma (Erlang) Noises to Each Image Channel [R, G, B]. 
R_GNoisy = Rframe + GN_R;
G_GNoisy = Gframe + GN_G;
B_GNoisy = Bframe + GN_B;
% // Construct Noisy Images from The Corresponding Noisy Channels.
Img_UNoisy = cat(3, R_UNoisy, G_UNoisy, B_UNoisy);
Img_RNoisy = cat(3, R_RNoisy, G_RNoisy, B_RNoisy);
Img_ENoisy = cat(3, R_ENoisy, G_ENoisy, B_ENoisy);
Img_GNoisy = cat(3, R_GNoisy, G_GNoisy, B_GNoisy);
% // Display Images
figure
subplot(1, 5, 1), imshow(img), title('Original image')
subplot(1, 5, 2), imshow(Img_UNoisy), title('Noisy image, Noise = Uniform')
subplot(1, 5, 3), imshow(Img_RNoisy), title('Noisy image, Noise = Rayleigh')
subplot(1, 5, 4), imshow(Img_ENoisy), title('Noisy image, Noise = exponential')
subplot(1, 5, 5), imshow(Img_GNoisy), title('Noisy image, Noise = Erlang')
% // Save Images to .bmp files
imwrite(Img_UNoisy,'output/Noise_Uni.bmp');
imwrite(Img_RNoisy,'output/Noise_Ray.bmp');
imwrite(Img_ENoisy,'output/Noise_Exp.bmp');
imwrite(Img_GNoisy,'output/Noise_Ga.bmp');

Any ideas why code is not working?

[Dyuman Joshi]

imnoise2 is not an inbuilt function nor a part of any toolbox function.

Do you have a function named imnoise2, which is in the current directory?

[Dimitriy]

No, I don't have.

Answer 1

[John D'Errico]

which imnoise2 -all

'imnoise2' not found.

We cannot help you to use a function that does not exist as part of MATLAB,

Possibly, the code you are using (since it was clearly not written by you) uses a code called imnoise2 as found on the file exchange. A quick search finds at least two places where it may have come from.

https://www.mathworks.com/matlabcentral/fileexchange/107519-dipnum?s_tid=srchtitle

Another is in this next contribution. Possibly they are the same function, as the first link seems to be a complete toolbox.

https://www.mathworks.com/matlabcentral/fileexchange/28986-adding-noise-and-image-restoration?s_tid=srchtitle

[Dimitriy]

These links did not help me. What do I need in order for this to work?

[Dyuman Joshi]

You need to download the file (the file will be downloaded as a zip file) and open/save it in the current directory. Then run the code.

Answer 2

[Image Analyst]

Try using the imnoise function of the Image Processing Toolbox instead of imnoise2 (which we don't know what that is).