matrix dimensions must agree error

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Lefteris Kostakis
Lefteris Kostakis 2019-11-22
评论： Image Analyst 2019-11-22
%I want to use dct2 to an image array and quantize 4x4 blocks of the image
%but in [afteral]=quantization(imafter,25); command it says "matrix dimensions must agree"
%IGNORE integer_transform its just another function I use.
frame178=imread("frame178.tif");
quantize = @(block_struct) integer_transform(dct2(block_struct.data));
imafter = blockproc(frame178,[4 4],quantize);
[afteral]= quantization(imafter,25);
%the function :
function [Z] = quantization(W,QP)
Z = round(W.*(M/2^q));
%THIS IS THE FUNCTION DEFINITION AND THE LINE WHERE IS THE ERROR
%M and q are defined before in the function M is a matrix with some factors and q is an integer
%I assume Z the error is the inserted matrix M that is different size from Z but when I do
%multiply with x.*y dont I multiply all elements of an array(W) with an integer from a matrix(M)? so why to have size error there?

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Image Analyst
Image Analyst 2019-11-22
编辑：Image Analyst 2019-11-22
It's not Z that matters. It's W.
What does this report in the command window if you put it before that Z line:
whos W
whos M
whos q
  2 个评论
Lefteris Kostakis
Lefteris Kostakis 2019-11-22
W 144x176 double (the parameter in function is array frame178 and its also 144x176 but not double it is uint8)
M 4x4 double
q 1x1 double
Image Analyst
Image Analyst 2019-11-22
So why do you think it's okay to do an element-by-element operation of a 144x176 matrix by a 4x4 matrix?
What happens when it goes to multiply W(5, 1) by M(5, 1) when there is no M(5,1)?
It can't multiply elements when the elements are not there.

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