解释一下以下这段Matlab程序的意思
如题，解释一下这段程序的意思，最好一句一句解释，是关于手写数字识别的
function Bool = TrainsFea(num,para)
N = 30;
f = imread(strcat(num2str(num),'.bmp'));
plate = (f(:,:,1) == 255) & (f(:,:,2) == 0) & (f(:,:,3) == 0) ;
f = rgb2gray(f);
f(plate == 1) = 255;
% imshow(f);
startPoints = [];
for t = 1:N
startPoints = [startPoints;[1+floor((t-1)/10)*144, 1+mod(t-1,10)*96]];
end
ims = {};
for t = 1: N
ims = [ims, f(startPoints(t,1):startPoints(t,1)+143, startPoints(t,2):startPoints(t,2)+95)];
end
if nargin == 2
figure;
for t = 1:N
subplot(N/10,10,t);
image(ims{t});
axis off;
end
end
Feature = [];
for t = 1:N
Feature = [Feature;HandWritings(ims{t})];
end
clear f ims plate startPoints t para num
if ~exist('pattern.mat')
disp('Initiated ');
pattern.feature = Feature;
pattern.patternNum = N;
clear Feature
save pattern;
elseif exist('pattern.mat')
disp('Exist ');
load('pattern.mat');
pattern2.feature = Feature;
pattern2.patternNum = N;
pattern = [pattern, pattern2];
clear pattern2 Feature
save pattern;
end
Bool = true;
