CODEWITHSUNDEEP
matlabmatrix-multiplicationimage-segmentation
Adham shafik
Adham shafik

Reputation: 1044

How to multiply binary image and rgb image in matlab?

I have a binary image which is the segmented form of another color image .

As you know , a binary image is 2-d but an rgb image is 3-d , how can i multiply them together ?

i tried this code which resulted in a strange pic 

function  skinCrop(bwSkin,colorSkin)

for i = 1:size(colorSkin,1)
    for j = 1:size(colorSkin,1)
        if bwSkin(i,j) == 0
            colorSkin(i,j,:) = 0;
        end
    end
end
imshow(colorSkin);
end

The original image was enter image description here

The resulting image was :

enter image description here

I expected it to be a hand against a dark background , so why do the right part appear that way ?

Upvotes: 1

Views: 4950

Answers (3)

Shai
Shai

Reputation: 114926

A more efficient way to do the multiplication is

function mult = skinCrop( bwSkin, colorSkin )
% 
% multiplying 3D color image with 2D mask
%

mult = nsxfun( @times, bwSkin, colorSkin );

% show the result
imshow( mult ); title('skin cropped image');

As @zenopy noted, you might need to cast your variable to double type.

Upvotes: 0

zenpoy
zenpoy

Reputation: 20136

You should avoid loops when not needed in matlab:

mask = cat(3,bwSkin,bwSkin,bwSkin);
output = mask.*colorSkin;

You might have to change the types in order for the multiplication to succeed:

output = uint8(mask).*colorSkin;

Or:

output = double(mask).*colorSkin;

Upvotes: 2

Justin Peel
Justin Peel

Reputation: 47082

You are using the wrong dimension length for your second dimension:

for j = 1:size(colorSkin,1)

should be

for j = 1:size(colorSkin,2)

Upvotes: 1

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