MATLAB imread（）无法读取旧图像？

Question

So I ran into a weird problem with the MATLAB imread() function where it can't read old images (in this case, a bmp from 2002). Basically when I pass the image as an argument to imread(), it recognises the image as a grayscale even though it is clearly RGB.

Image is part of a standard test set available to download from here . I am using the 'boy.bmp' image.

% In Downloads folder    
I_dl = imread('boy.bmp');
whos %to show current variables

OUTPUT:

Name                    Size                 Bytes  Class     Attributes
I_dl                  512x768               393216  uint8               

The image size is actually around 390KB so it's not that only one channel is getting loaded into the workspace somehow. Looks like it has to do with some older encoding system.

I ran an imshow() to check the image and this was the result.

TEMPORARY WORK-AROUND: I imported the image into GIMP, saved it as an xcf (GIMP's native format) and then exported it as a bmp. Then I did the imread() and then whos . It works.

Name                    Size                 Bytes  Class     Attributes
I                     512x768x3            1179648  uint8               

The file size expanded to 1.2MB too. Strange.

Any one else faced the same issue?

Regards.

Answer 1

boy.bmp contains the indexed image . You should load and use the colormap matrix:

[I_dl,cmap] = imread('boy.bmp');
imshow(I_dl,cmap);