How to multiply a matrix by a boolean mask

Hello. I'm trying to multiply an image matrix by a roipoly boolean mask.

It's throwing a 'Matrix dimensions must agree' error in the BlendImages function as shown below. I understand that the mask is a boolean and therefore does not have the same dimensions as the matrix I'm trying to multiply it with.

The image dimensions: 480x640x3 double

Boolean mask dimensions: 480x640 double

How do I convert the boolean mask so that I can multiply the image with it? Any help would be much appreciated.

   im1 = double(imread('image1.jpg'))/255;
  im2 = double(imread('image2.jpg'))/255;
  level = 4;

   ...

   figure; imshow(im1);
   mask = roipoly;
   close;

% image1_laplacian and image2_laplacian are both cell arrays of images
 blended = BlendImages(image1_laplacian, image2_laplacian, mask, level);

BlendImages function:

function blendedImage = BlendImages(pyr1, pyr2, mask, level)

maskImage = double(mask)/255;
pyr1_mask = GaussianPyramid(maskImage, level);
pyr2_mask = GaussianPyramid(1 - mask, level);
pyr_combined = cell(level, 1);
for i=1:level
  % * ERROR ON NEXT LINE *
   pyr_combined{i} = (pyr1{i} .* pyr1_mask{i}) + (pyr2{i} .* pyr2_mask{i});
    figure; imshow(pyr_combined);
end

Answer 1

[Image Analyst]

Try it Sean's way:

% An alternate method to multiplication channel by channel.
% Mask the image using bsxfun() function
maskedRgbImage = bsxfun(@times, rgbImage, cast(mask, class(rgbImage)));

[t]

Thanks for the answer but I'm still having troubles. Essentially what i'm trying to do is 'cut' the mask out of the image. Is this the right way to go about it? Thanks.

[Image Analyst]

If you want to crop, use imcrop().

[t]

Not crop exactly. I apply gaussian blur to the mask. What I want to know how to do is then multiply this blurred mask by the image. Is there a way of doing this? Many thanks.

[Image Analyst]

Use fspecial to create the Gaussian window. Then create your mask. Cast it to double and use conv2() or imfilter() to blur the mask by the Gaussian. Then cast your grayscale image to double and do a dot-multiply to multiply it

g = fspecial(.............. whatever.......);
blurredMask = conv2(mask, g, 'same');
m = (double)grayImage .* blurredMask;