matlab批量转化img到gray

path = 'D:\宝贝儿数据集\COIL-3D\coil-100\';
save_path = 'D:\宝贝儿数据集\COIL-3D\coil-100-gray\';
file=dir([path,'*.png']);

for i=1:length(file)
    I=imread([path,file(i).name]);
    I=rgb2gray(I);
    imshow(I);
    imwrite(I,[save_path,file(i).name]);
end