function [ top, bottom, middle, len ] = classify_by_vertical_white_belt( img )

% 垂直搜索图片中的白段, 记录具体信息.

% top: 白段的上分位点数组, bottom: 下分位点数组,

% middle: 各白段纵坐标中点, len: 各白段长度.

% 此处显示详细说明

[h, w] = size(img);

start = 0;

idx = 1;

top = zeros(1);

bottom = zeros(1);

middle = zeros(1);

len = zeros(1);

for i = 1 : h

if all(img(i, :) == 1) && (start == 0)

t_top = i;

start = start + 1;

end

if any(img(i, :) == 0) && (start > 0)

t_bottom = i;

if t_bottom - t_top > 6 && t_bottom - t_top < 22

bottom(idx) = t_bottom;

top(idx) = t_top;

middle(idx) = round((bottom(idx) + top(idx)) / 2);

len(idx) = bottom(idx) - top(idx);

idx = idx + 1;

end

start = 0;

end

end

end