Algorithm 1 Generation of a color palette
Input: a sequence of n brain wave samples s1, s2, …, sn in a duration of 20 s with each si consisting of the two features of attention and meditation represented by variables ai and mi, respectively, i.e., si = (ai, mi).
Output: a color palette H consisting of four strips of colors of blue, green, orange, and aubergine from left to right representing the emotion types of focusing, relaxation, calmness, and anxiety, respectively.
Steps.
Step 1:	//Initialization
1.1 denote the four emotion types of focusing, relaxation, calmness, and anxiety by Fi, Ri, Ci, and Ai, respectively;
1.2 set up four counters Ftotal, Ttotal, Ctotal, and Atotal for Fi, Ri, Ci, and Ai, respectively.
Step 2:	//Classifying the brain waves
for i = 1 to n do
(a) classify si = (ai, mi) as one of Fi, Ri, Ci, and Ai according to rules specified by Equation (1), and denote the result by Xi;
(b) increment the counters according to Xi in the following way:	//Computing sums
(i) if Xi = Fi, then set Ftotal = Ftotal + 1;
end if;	//Ftotal = # blue samples
(ii) if Xi = Ri, then set Rtotal = Rtotal + 1;
end if;	//Rtotal = # green samples
(iii) if Xi = Ci, then set Ctotal = Ctotal + 1;
end if;	//Ctotal = # orange samples
(iv) if Xi = Ai, then set Atotal = Atotal + 1;
end if;	//Atotal = # aubergine samples
end for.
Step 3:	//Computing the color ratios and transforming them into 0~3
compute the following integers as the color weights:
f = ⎣(Ftotal/n) × 4⎦, r = ⎣(Rtotal/n) × 4⎦; c = ⎣(Ctotal/n) × 4⎦; and a = ⎣(Atotal/n) × 4⎦.
Step 4:	//Creating the color palette
4.1 create a rectangular shape H of size 4w × h pixels;
//The unit width w and unit height h are pre-determined
4.2 fill H with blue-, green-, orange-, and aubergine-colored strips of the widths of f×w, r×w, c×w, and a×w pixels, respectively;
4.3 smear the boundary between every two different colors in H to create a color gradient effect within a distance of (1/3)×w from the boundary.
//Making the created color palette look more natural
Step 5:	//Ending
exit with H as the desired color palette.