matlab - Is it possible to multiply a 3x3 matrix (a color transformation) with a rank 3 tensor/3D matrix (a color image)? -

when images read in, converted matrices/tensors of dimension (x,y,3) last 1 r, g, b channels.

i looking apply colorspace conversion, that's 3x3 matrix want apply each pixel. i'm sort of looking here "component wise" matrix-vector multiply.

can done matlab/octave? i'm using octave seems if there's way matlab should have fighting chance octave.

i'm getting this:

octave:15> b b =     0.9465229   0.2946927  -0.1313419   -0.1179179   0.9929960   0.0073716    0.0923046  -0.0464579   0.9946464  octave:16> b * y error: invalid conversion of ndarray matrix 

i guess gotta nested loop manually. when try this:

blena = lena; %// copy structure -- here lena rgb image of type double i=1:rows(lena)   j=1:columns(lena)     blena(i,j) = b * lena(i,j,:);   endfor endfor 

lena(i,j,:) still ndarray.

sure. need reshapeing:

im = rand(100,150,3); %// example "image" t = rand(3,3); %// example transform matrix result = reshape((t * reshape(im, [], 3).').', size(im)); 

this arranges original image 3-row matrix (each row color component, each column pixel), matrix multiplication, , puts shape.