令存为C:\Documents and Settings\Administrator\桌面\1.jpg
>> I=imread('C:\Documents and Settings\Administrator\桌面\1.jpg');
J=I(:,:,1)<200;
II=I(:,:,1);II(J)=0;I(:,:,1)=II;
II=I(:,:,2);II(J)=0;I(:,:,2)=II;
II=I(:,:,3);II(J)=255;I(:,:,3)=II;
imshow(I)
>>