Matrix multiplication within a function not working

The following function creates a column vector and an image histogram:

function lutlum = lutlummer(image)
    for i = 1:1:265
    lutlum(i, 1) = i-1;
    end
    
   %multiplying the LUT with the luminescence histogram of the image 
   %Finding luminance image 'L' (Formula gained from class slides)
   L = uint8(sum(bsxfun(@times,double(image),reshape([0.299 0.587 0.114],[1 1 3])),3));
   %Finding luminance histogram'HL'
   HL = histcounts(L,[0:256])';
   lutlum = lutlum*HL;

end

The function is called with an image such that HL is a 1x2 matrix, so multiplying a 265x1 matrix ('lutlum') with a 1x2 matrix should be no problem. however, i still get this message:

Matrix dimensions must agree.

Error in ImageProcessingLab2>lutlummer (line 469)

lutlum = lutlum.*HL;

Please do let me know where i am going wrong

thanking yall in advance!! :D

[Image Analyst]

image is a built-in function. Do not use it as the name of an input variable.

What is the size of your image?

[Bharath Nagarajan]

Dully note, thank you for tyhe feedback! my image is 387x713x3

[Image Analyst]

What is L? Is it the gray scale version of the color image like you'd get from rgb2gray()? If so, why would you multiply the 1-D histogram bin count by a 2-D image?

[Bharath Nagarajan]

L is supposed to be the 'Luminescence image' and it appears that it is a greyscale image. Howvere, I am trying to multiply lutlum (256x1 matrix) with HL (a 1x2 matrix). this should still work though right? since the matrix dimentions are compatable?

Answer 1

[Sulaymon Eshkabilov]

There is an err, here is how it is to be:

 lutlum = HL.'*lutlum;  % creates 2 - by - 256

[Bharath Nagarajan]

Unfortunately it still throws the same error

Error using *

Incorrect dimensions for matrix multiplication. Check that the number of columns in the first matrix matches the number of rows in the second matrix. To perform elementwise multiplication, use '.*'.

Error in ImageProcessingLab2>lutlummer (line 481)

lutlum = lutlum.'*HL;

and even when the order of matrices are switched:

Error using *

Incorrect dimensions for matrix multiplication. Check that the number of columns in the first matrix matches the number of rows in the second matrix. To perform elementwise multiplication, use '.*'.

Error in ImageProcessingLab2>lutlummer (line 481)

lutlum = HL.'*lutlum;

Answer 2

[Sulaymon Eshkabilov]

There are a couple of errs in the code. Here is the corrected version:

function lutlum = lutlummer(image)
    for i = 1:1:256    % Has to be 256 NOT 265. 256 similar to 265 :)
    lutlum(i, 1) = i-1;
    end
   
   %multiplying the LUT with the luminescence histogram of the image 
   %Finding luminance image 'L' (Formula gained from class slides)
   L = uint8(sum(bsxfun(@times,double(image),reshape([0.299 0.587 0.114],[1 1 3])),3));
   %Finding luminance histogram'HL'
   HL = histcounts(L,[0:256])';   % Note the size of HL is 256 - by - 1 NOT [1 - by - 2] as you have stated  
   lutlum = lutlum*HL';           % Transpose is necessary

end