# Is there a way to overcome For loops for fast processing?

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Muhammad Farhan Mughal on 9 Sep 2019
Commented: darova on 10 Sep 2019
I have written a following MATLAB code to detect skin color pixels from the RGB image. The output is as expected but being pixel by pixel algorithm, my program is taking too long, expecially for high quality images. Is there a way to take out the for loops for fast processing? Thank you.
[s1,s2,s3] = size(I);
skin_img1 = zeros(s1,s2,s3);
maxR = max(max(R));
minR = min(min(R));
maxG = max(max(G))
minG = min(min(G));
maxB = max(max(B));
minB = min(min(B));
for i = 1:s1
for j = 1:s2
if R(i,j)>90/255
if ( G(i,j)>40/255 && B(i,j)>20/255 && abs(R(i,j)-G(i,j))>15/255 && R(i,j)> G(i,j) && R(i,j) > B(i,j)...
&& (max([R(i,j),G(i,j),B(i,j)])- min([R(i,j),G(i,j),B(i,j)]) >15/255));
% (maxR - minR)>15/255 && (maxG - minG)>15/255 && (maxB - minB)>15/255 )
skin_img1(i,j,:) = I (i,j,:);
end
% else
% if( R(i,j)> G(i,j) && R(i,j) > B(i,j) && R(i,j) - G(i,j)> 5/255 && (abs(G(i,j)-B(i,j))>5/255))
% Skin_Image(i,j,:) = I (i,j,:);
% end
end
end
end

KALYAN ACHARJYA on 9 Sep 2019
Attach sample image, so that we can try on it? Skin color?
Muhammad Farhan Mughal on 10 Sep 2019
One of the figure from internet is

Muhammad Farhan Mughal on 10 Sep 2019
Following MATLAB code significantly reduced the computatonal cost of the questioned code
R = I(:,:,1);
G = I(:,:,2);
B = I(:,:,3);
R = double(R);
G = double(G);
B = double(B);
R = R/255;
G = G/255;
B = B/255;
[s1,s2,s3] = size(I);
skin_img1 = zeros(s1,s2,s3);
index1 = zeros(size(R));
R1 = R(:) ; G1 = R(:); B1 = B(:);
mat_I = [R1,G1,B1]';
index = R >90/255 & G > 40/255 & B>20/255 & abs(R-G)>15/255 & R> G & R > B &...
reshape((max(mat_I)- min(mat_I)) >15/255, [s1,s2]);
index = uint8(index);
skin_img = repmat(index,[1,1,3]).*I;

darova on 10 Sep 2019
Can i use your code for my study research?
Not for commercial purposes
Muhammad Farhan Mughal on 10 Sep 2019
Yes, you can I also wrote that code for research purposes.
darova on 10 Sep 2019

darova on 9 Sep 2019
See attached script
clc, clear
subplot(1,2,1)
imshow(A)
RGB = [40 120 40]; % color you want
e = 40; % color shift / deviation
B = pix_in(A,RGB,e);
B = B + 255.*uint8(~B); % choosing white background
subplot(1,2,2)
imshow(B)