Automatic Foreground Extraction Based on Difference of Gaussian

Algorithm 1

Extraction Algorithm.

(1)     Input: 𝑖𝑚𝑎𝑔𝑒, 𝑡ℎ𝑟𝑒𝑠ℎ, 𝑁𝑐𝑢𝑡𝑁𝑢𝑚;

(2)    Loading image data: 𝐼𝑚𝑅𝐺𝐵=𝑖𝑚𝑟𝑒𝑎𝑑("𝑖𝑚𝑎𝑔𝑒");

(3)    Image segmentation with Ncut: 𝐼𝑚𝑁𝑢𝑡=𝑁𝑐𝑢𝑡(𝐼𝑚𝑅𝐺𝐵,𝑁𝑐𝑢𝑡𝑁𝑢𝑚);

(4)    Boundary computing: 𝐼𝑚𝐵𝑜𝑢𝑛𝑑𝑎𝑟𝑦=𝐹𝑖𝑛𝑑𝐵𝑜𝑢𝑛𝑑𝑎𝑟𝑦(𝐼𝑚𝑁𝑐𝑢𝑡));

(5)    Initial the keypoints set: 𝐾𝑒𝑦𝑝𝑜𝑖𝑛𝑡=𝑧𝑒𝑟𝑜𝑠(𝑠𝑖𝑧𝑒(𝐼𝑚𝑅𝐺𝐵));

(6)    Computing the candidate points by difference of Gaussian (DoG):

(7)    for  𝑛=1∶3  do

(8)     Loading single layer data: 𝐼𝑚𝐿𝑎𝑦=𝐼𝑚𝑅𝐺𝐵(∶,∶,𝑛);

(9)     Detecting the keypoints with DoG: 𝐼𝑚𝑙𝑎𝑦𝐷𝑜𝐺=𝐷𝑜𝐺(𝐼𝑚𝐿𝑎𝑦);

(10)   Edge detection: 𝐼𝑚𝐸𝑑𝑔𝑒=𝑒𝑑𝑔𝑒(𝐼𝑚𝑙𝑎𝑦𝐷𝑜𝑔);

(11)    Finding Focus: 𝐼𝑚𝐹=𝐹𝑖𝑛𝑑𝐹𝑜𝑐𝑢𝑠(𝐼𝑚𝐸𝑑𝑔𝑒);

(12)   Rebuilding keypoints:

          𝐿𝑎𝑦𝑒𝑟𝐾𝑒𝑦𝑝𝑜𝑖𝑛𝑡(𝑛)=𝑅𝑒𝑏𝑢𝑖𝑙𝑑(𝐼𝑚𝐸𝑑𝑔𝑒,𝐼𝑚𝐹,𝐼𝑚𝐵𝑜𝑢𝑛𝑑𝑎𝑟𝑦));

(13)  end for

(14)  Combining the keypoints with the three layers:

          𝐼𝑚𝐾𝑒𝑦𝑝𝑜𝑖𝑛𝑡=𝑢𝑛𝑖𝑜𝑛(𝐿𝑎𝑦𝑒𝑟𝐾𝑒𝑦𝑝𝑜𝑖𝑛𝑡);

(15)  Locating the foreground regions by the numbers of keyponts:

(16)  for  𝑛=1∶𝑁𝑐𝑢𝑡𝑁𝑢𝑚  do

(17)   Initial the number of keypoints and the total pixels of the 𝑛th region:

        𝑇𝑜𝑡𝑎𝑙𝐾𝑒𝑦𝑝𝑜𝑖𝑛𝑡𝑠=0; 𝑁𝑢𝑚𝐾𝑒𝑦𝑝𝑜𝑖𝑛𝑡(𝑛)=0;

(18)   Calculating the total number of keypoints of each region:

(19)   for  𝑥=1∶𝑠𝑖𝑧𝑒(𝐼𝑚𝑅𝐺𝐵,1)  do

(20)   for  𝑦=1∶𝑠𝑖𝑧𝑒(𝐼𝑚𝑅𝐺𝐵,2)  do

(21)     if  𝐼𝑚𝑁𝑐𝑢𝑡(𝑥,𝑦)==𝑛  then

(22)     if  𝑎𝑏𝑠(𝐼𝑚𝐾𝑒𝑦𝑝𝑜𝑖𝑛𝑡(𝑥,𝑦))==1  then

(23)      𝑇𝑜𝑡𝑎𝑙𝐾𝑒𝑦𝑝𝑜𝑖𝑛𝑡𝑠=𝑇𝑜𝑡𝑎𝑙𝐾𝑒𝑦𝑝𝑜𝑖𝑛𝑡𝑠+1;

(24)      𝑁𝑢𝑚𝐾𝑒𝑦𝑝𝑜𝑖𝑛𝑡(𝑛)=𝑁𝑢𝑚𝐾𝑒𝑦𝑝𝑜𝑖𝑛𝑡(𝑛)+1;

(25)     end if

(26)    end if

(27)   end for

(28)  end for

(29)  Locating the foreground regions by the numbers of keyponts:

(30)  if  𝑁𝑢𝑚𝐾𝑒𝑦𝑝𝑜𝑖𝑛𝑡(𝑛)≤𝑡ℎ𝑟𝑒𝑠ℎ∗𝑇𝑜𝑡𝑎𝑙𝐾𝑒𝑦𝑝𝑜𝑖𝑛𝑡𝑠  then

(31)   for  (𝑥,𝑦)∈𝑅𝑒𝑔𝑖𝑜𝑛(𝑛)  do

(32)       𝐼𝑚𝑅𝐺𝐵(𝑥,𝑦,∶)=0;;

(33)   end for

(34)  end if

(35) end for

(36) Output: Foreground, 𝐹𝑜𝑟𝑒𝑔𝑟𝑜𝑢𝑛𝑑=𝐼𝑚𝑅𝐺𝐵;