MATLAB批量处理图像：真彩转黑白

clc;
clear all;
maindir = 'F:\skype';
subdir =  dir( maindir );   % 先确定子文件夹
for i = 1 : length( subdir ) 
    if( isequal( subdir( i ).name, '.' ) || ...    
            isequal( subdir( i ).name, '..' ) || ...      
            ~subdir( i ).isdir )   % 如果不是目录跳过       
        continue;    
    end
     
    subdirpath = fullfile( maindir, subdir( i ).name, '*.jpg' );
    images = dir( subdirpath );   % 在这个子文件夹下找后缀为jpg的文件
     
    for j = 1 : length( images ) % 遍历每张图片

        imagepath = fullfile( maindir, subdir( i ).name, images( j ).name  );
        rgb = imread( imagepath );   % 这里进行你的读取操作
        R=rgb(:,:,1); %red  
        G=rgb(:,:,2); %green  
        B=rgb(:,:,3); %blue  
        [x,y,z]=size(rgb);  
     for t =1:x
         for l =1:y  
          if( (R(t,l) == 0) && (G(t,l) == 0) && (B(t,l) == 0) )  
            R(t,l) = 255;  
            G(t,l) = 255;  
            B(t,l) = 255; 
          else 
            R(t,l) = 0;