Is their any substitue of blockproc for computing dct and quantizing the image

I am trying to do following

>> x = imread('cat.png'); >> [xm, xn] = size(x); >> x = double(x) - 128; >> T = dctmtx(8); >> dct = @(block_struct) T * block_struct.data * T'; >> D = blockproc(x,[8 8],dct);

Function BLOCKPROC encountered an error while evaluating the user supplied function handle, FUN.

The cause of the error was:

Error using * Inputs must be 2-D, or at least one input must be scalar. To compute elementwise TIMES, use TIMES (.*) instead.

Error in @(block_struct)T*block_struct.data*T'

Error in blockprocFunDispatcher (line 14) output_block = fun(block_struct);

Error in blockprocInMemory (line 81) [ul_output fun_nargout] = blockprocFunDispatcher(fun,block_struct,...

Error in blockproc (line 234) result_image = blockprocInMemory(source,fun,options);

Answer 1

[Walter Roberson]

It appears that you have assumed that imread() is going to return a 2D array. Suppose, though, it is an RGB image: then it would return a 3D array. Is dct even defined for 3D arrays? Perhaps you will need to process individual color planes.