What "blkproc(I,[8 8],'dct2')" means?

Hello everyone, I have question about blkproc function for image processing. If I do this code below,

T=dctmtx(8);
fun=@(block_struct) T*block_struct.data*T';
block=blkproc(I,[8 8],fun);

is that the same code with this?

 block=blkproc(I,[8 8],'dct2');

but when I do the first code, it results this error :

Attempt to reference field of non-structure array.
Error in @(block_struct)T*block_struct.data*T'
Error in blkproc (line 103)
firstBlock = feval(fun,x,params{:});
Error in analize (line 15)
blok2 = blkproc(I_subs,[8 8],fun);

what's wrong with the first code? thank you..

Answer 1

[Walter Roberson]

You are confusing blkproc() and blockproc()

[sabila nur]

I changed blkproc() to blockproc() on the first code, but I had this error :

Function BLOCKPROC encountered an error while evaluating the user supplied function
handle, FUN.
The cause of the error was:
Error using  * 
Inner matrix dimensions must agree.
Error in @(block_struct)T*block_struct.data*T'

What should I do?

[Dishant Arora]

 fun = @(block_struct) dct2(block_struct.data)
b = blockproc(Image,[8,8],fun);

[Walter Roberson]

Possibly you need

T .* block_struct.data .* T'

but I suspect that will not work either.

You should debug to see whether the error always occurs, or if instead the error is only occurring on a border. See the 'PadPartialBlocks' option.