selection of patches of an image

Dear sir,

I use superpixel segmentation algorithm for patch generation,the output image is attached.

I = imread('capture1.jpg');

[L,N] = superpixels(I,40);

figure

BW = boundarymask(L);

imshow(imoverlay(I,BW,'red'),'InitialMagnification',67)

Next I want to select only the foregrond area patches(black color) and compute the area,patch length and patch location of the patches.How it is possible?help me sir