Problem with blockprocess while using the block data for feature extraction

Hi,

I am using blockprocess for splitting the image into 10x10 overlapping image blocks and I want to extract features of these blocks but matlab is giving errors. The code for the task is pasted here.

The matlab error is

??? Error using ==> blockproc>userfunDispatcher at 719
There was an error when evaluating the user supplied function FUN.  The error message was:

Invalid filename.

Error in ==> blockproc at 214
output_block = userfunDispatcher(fun,input_struct,trim_border);

Error in ==> Main at 57
B= blockproc(g,[4 4],fun);%,'BorderSize',[3 3]); %[M + 2*V, N + 2*H]

Code:

fun=@(block_struct)feature_extraction(block_struct.data);
B= blockproc(g,[4 4],fun,'BorderSize',[3 3]);

Feature extraction function code

function features=feature_extraction(name_images)
[num_im,q]=size(name_images);
features=zeros(num_im,12);
for i=1:num_im
A=imread(name_images(i,:));
A=double(A);

%Normalization of the pixels intensity in [0, N_gray-1]
A=round((N_gray-1)*((A-min(A(:)))/(max(A(:))-min(A(:)))));

features(i,1)=mean2(A);
features(i,2)=std2(A);
features(i,3)=skewness(A(:));
features(i,4)=kurtosis(A(:));
end

kindly guide me what's wrong with it and how may i fix it. is there any alternate way to do it

Answer 1

[Image Analyst]

You forgot to post the error! In the meantime, check out these two demos for how to use blockproc().

There is also a FAQ entry on non -overlapping blocks, http://matlab.wikia.com/wiki/FAQ#How_do_I_split_an_image_into_non-overlapping_blocks.3F. If you want overlapping blocks, then if they overlap by all but one pixel as they slide along, then you should use nlfilter() instead of blockproc(). Overlaps of other amounts are not very common. Why do you want overlap?

[Arslan Ahmad]

I want overlaps because there is a possibility that in non overlapping windows the point of interest would be divided

Answer 2

[Image Analyst]

You can't do this:

B=1 blockproc(g,[4 4],fun,'BorderSize',[3 3]);

You have a one, then a space, then a blockproc call. Why is the 1 and a space there????

[Arslan Ahmad]

I am sry there is mistake while writing the code here I edited it now

[Arslan Ahmad]

@image Analyst

I have edited the question now and also have pasted the error.

[Image Analyst]

I still don't see the actual error - only line numbers on which it occurs. Can you copy all the red text - ALL of it, not just part of it.

[Arslan Ahmad]

@Image Analyst

Dear I have now pasted the complete error message and edited the question once again.

[Image Analyst]

Wow, you're not making it easy for us to help you, are you? Now it's asking for g. Why don't you just attach the m-file that will reproduce your error? By the way, did you ever look at the demos I uploaded for you? One of them shows how to run blockproc() with a custom defined function like you want to do. Did you try to follow that example???

[Arslan Ahmad]

@image Analyst

Dear I am trying to make it easy for you to help me. I am working on your demo as well. I am really grateful for the help.I have uploaded the files as well.

[Image Analyst]

This is the error message I got. I'm not sure why you didn't get all this. Maybe it's because you have an old version.

>> blockprocFunDispatcher
Undefined function or variable 'blockprocFunDispatcher'. 
>> blockprocFunDispatcher
Undefined function or variable 'blockprocFunDispatcher'. 
>> test3
Function BLOCKPROC encountered an error while evaluating the user supplied function handle, FUN.

The cause of the error was:

Error using imread>parse_inputs (line 457)
The filename or url argument must be a string.
Error in imread (line 316)
[filename, fmt_s, extraArgs] = parse_inputs(varargin{:});
Error in test3>feature_extraction (line 13)
  A=imread(name_images(i,:));
Error in test3>@(block_struct)feature_extraction(block_struct.data) (line 5)
fun=@(block_struct)feature_extraction(block_struct.data);
Error in blockprocFunDispatcher (line 13)
        output_block = fun(block_struct);
Error in blockprocInMemory (line 80)
[ul_output fun_nargout] = blockprocFunDispatcher(fun,block_struct,...
Error in blockproc (line 236)
    result_image = blockprocInMemory(source,fun,options);
Error in test3 (line 6)
B= blockproc(g,[4 4],fun,'BorderSize',[3 3]);

Basically the problem looks to be this line:

A=imread(name_images(i,:));

Now, name_images is not a string, but you're trying to treat it as one. I think it's a structure. Once you understand my demo you'll know how to handle the submimage input into your custom function. Why don't you set a breakpoint in the function and step through it to see what's going on? Using the debugger yourself is a lot faster than posting message here.

[Arslan Ahmad]

@Image Analyst

Dear Sir,

I am very much grateful for your help. The error was with the function its working now.