帮我解读一下这个图像处理的matlab程序中的几个地方

Question

%文件读取
clear;
clc;

file_name = input('请输入图像文件路径：','s');
I_rgb = imread(file_name); %读取文件数据
%figure();
%imshow(I_rgb); %显示原图
%title('原始图像'); %将彩色图像从RGB转化到lab彩色空间
C = makecform('srgb2lab'); %设置转换格式
I_lab = applycform(I_rgb, C); %进行K-mean聚类将图像分割成3个区域
ab = double(I_lab(:,:,2:3)); %取出lab空间的a分量和b分量
nrows = size(ab,1);
ncols = size(ab,2);
ab = reshape(ab,nrows*ncols,2);
nColors = 3; %分割的区域个数为3
[cluster_idx cluster_center] = kmeans(ab,nColors,'distance','sqEuclidean','Replicates',3); %重复聚类3次
pixel_labels = reshape(cluster_idx,nrows,ncols);
%figure();
%imshow(pixel_labels,[]), title('聚类结果'); %显示分割后的各个区域
segmented_images = cell(1,3);
rgb_label = repmat(pixel_labels,[1 1 3]);
for k = 1:nColors
color = I_rgb;
color(rgb_label ~= k) = 0;
segmented_images{k} = color;
end
figure(),imshow(segmented_images{1}), title('分割结果——区域1');
figure(),imshow(segmented_images{2}), title('分割结果——区域2');
figure(),imshow(segmented_images{3}), title('分割结果——区域3');

就是下面这几句

ab = double(I_lab(:,:,2:3)); %取出lab空间的a分量和b分量
nrows = size(ab,1);
ncols = size(ab,2);
ab = reshape(ab,nrows*ncols,2);
nColors = 3; %分割的区域个数为3
[cluster_idx cluster_center] = kmeans(ab,nColors,'distance','sqEuclidean','Replicates',3); %重复聚类3次
pixel_labels = reshape(cluster_idx,nrows,ncols);

Answer 1

ab = double(I_lab(:,:,2:3)); %把I_lab(:,:,2:3）转变为double类型数据
nrows = size(ab,1); %得到ab的行的长度
ncols = size(ab,2); %得到ab的列的长度
ab = reshape(ab,nrows*ncols,2); %改变矩阵的列数和行数，但是数据总个数不变
nColors = 3; %分割的区域个数为3
[cluster_idx cluster_center] = kmeans(ab,nColors,'distance','sqEuclidean','Replicates',3); %重复聚类3次
pixel_labels = reshape(cluster_idx,nrows,ncols);%改变矩阵的列数和行数

我很认真在回答，采纳咩