Add salt or pepper or random valued impulse noise to image

This function add wither salt or pepper or both type or random valued impulse noise to image.

% Add salt or pepper noise to image of certain density
% image_noisy = pepperOrSalt(image_orig, ND, type_noise, min_val, max_val)
% image_noisy = image after adding salt or pepper or both salt and pepper noise
% image_orig = image after adding salt or pepper or both salt and pepper noise
% ND = noise density, default value is 0.2(20% noise)
% type_noise = decides whether to add salt or pepper or both type of noise,
% value of 1 for pepper, 2 for salt and 3 for both salt and pepper noise.
% Default value is 3(both salt and pepper will be added in case od default value)
% min_val = the value of minimum noise. Value of 0 for pepper noise.
% Different value should be assigned to min_val in case of random valued
% impulse noise
% max_val = the value of maximum noise. Value of 1 for pepper noise in case of image with range [0,1]
% whereas value of 255 should be assigned in case of image with range
% [0,255].
% Different value should be assigned to max_val in case of random valued
% impulse noise
%%
function img = pepperOrSalt(varargin)
if length(varargin) == 1
img = varargin{1};
ND = 0.2;
type_noise = 3;

class_img = class(img);
min_val = 0;
if(isa(class_img ,'uint8'))
max_val = 255;
else
max_val = 255;
end
elseif length(varargin) < 3
img = varargin{1};
ND = varargin{2};
type_noise = 3;
class_img = class(img);
min_val = 0;
if(isa(class_img ,'uint8'))
max_val = 255;
else
max_val = 1;
end
elseif length(varargin) == 3
img = varargin{1};
ND = varargin{2};
type_noise = varargin{3};

class_img = class(img);
min_val = 0;
if(isa(class_img ,'uint8'))
max_val = 255;
else
max_val = 1;
end
elseif length(varargin) == 4
img = varargin{1};
ND = varargin{2};
type_noise = varargin{3};
min_val = varargin{4};
class_img = class(img);
if(isa(class_img ,'uint8'))
max_val = 255;
else
max_val = 1;
end
max_val = max(img(:));
elseif length(varargin) >= 5
img = varargin{1};
ND = varargin{2};
type_noise = varargin{3};
min_val = varargin{4};
max_val = varargin{5};
else
disp('not enough input parameter');
img = 0;
return;
end
Narr = rand(size(img));
if type_noise == 1

img(Narr<ND) = min_val;

elseif type_noise == 2

img(Narr<ND) = max_val;

else

img(Narr<ND/2) = min_val;
img((Narr>=ND/2)&(Narr<ND)) = max_val;

end