A MATLAB function to generate a mask for playing cards

card_mask.m

function mask=card_mask(img)
    BW_a=imbinarize(img,'adaptive');
    BW_g=imbinarize(img,'global');
    cc_a=bwconncomp(BW_a,4);
    cc_g=bwconncomp(BW_g,4);
    obj_sizes_a=cellfun('length',cc_a.PixelIdxList);
    obj_sizes_g=cellfun('length',cc_g.PixelIdxList);
    [px_count_a,idx_a]=max(obj_sizes_a);
    [px_count_g,idx_g]=max(obj_sizes_g);
    mask=false(size(img));
    mask_idx=intersect(cc_a.PixelIdxList{idx_a},cc_g.PixelIdxList{idx_g});
    mask(mask_idx)=true;
    mask=imfill(mask,'holes');
end