how i can get a filename from an image proviously defined

hello.

how i can get a filename from an image previously defined.

a= imread('100126_122731 tamp1.jpg');
b=rgb2gray(a);
imshow(b)
dct2(b,10,10)--> i get error here.

this is the function of dct2:

%% LOSSY COMPRESSION-DECOMPRESSION USNIG DISCRETE COSINE TRANSFORM TECHNIQUE.
function[]=dct2(filename,n,m)
% "filename" is the string of characters including Image name and its
% extension.
% "n" denotes the number of bits per pixel.
% "m" denotes the number of most significant bits (MSB) of DCT Coefficients. 

EDIT: two hundred lines of superfluous, copyright code removed. Original file:

https://www.mathworks.com/matlabcentral/fileexchange/57611-dct

[Stephen23]

@sudarti siburian: note that that function is badly named, because it shadows the inbuilt dct2 function:

https://www.mathworks.com/help/images/ref/dct2.htmlhttps://www.mathworks.com/help/images/ref/dct2.html

You should rename that function (check the name first using which).

[sudarti siburian]

thank you. i have rename that function, but it still error

error using imread>parse>parse_inputs

the file name or URL argument must be a string

[Stephen23]

Sure, and my answer shows you how to avoid that error.

Answer 1

[Stephen23]

fnm = '100126_122731 tamp1.jpg';
a = imread(fnm);
b = rgb2gray(a);
imshow(b)
dct2(fnm,10,10)

[sudarti siburian]

thank you.

but i want use the variable 'b' for function dct2

[Image Analyst]

Then pass in b:

myDct2(fnm, b, whateverYouWant, pi);

just make sure that the corresponding arguments in myDct2 match up.

The names in the definition of myDct2 don't need to have the same names as the variables in the calling routine of course. They can be different if you want. For example, you can pass in fnm like Stephen did but you can still call it filename like you did in your function definition.

[Stephen23]

"but i want use the variable 'b' for function dct2"

The first input argument of the function you have shown us is clearly defined in its help as: '"filename" is the string of characters including Image name and its extension.' Is your variable b a character string with a filename? No, it is not, it is a numeric array.

Perhaps this confusion occured because you read MATLAB's dct2 help (which does indeed require a numeric array as its first input argument) and have somehow confused this for some random code that you have downloaded. Your third-party function is totally unrelated to MATLAB's dct2 function, and there is absolutely no reason why their inputs have to be similar in any way (and in case it is not clear to you yet, they aren't).

[Stephen23]

sudarti siburian's "Answer" moved here:

thank you for all of you. i have get it

[Stephen23]

@sudarti siburian: do not forget to accept the answer that helps you to resolve your question!