JPG to RGB image?

I'm using a method that requires an rgb image as input. I tried

 [cdata,map] = imread('face.jpg' ) 
 cdata = ind2rgb( cdata, map );

to get that rgb image in cdata. However, map is always empty, no matter what image I try (jpg, tif, or bmp), resulting in the error "Index exceeds matrix dimensions." cdata is an mxnx3 matrix, I expected it to be just an mxn matrix?

I have no idea how to get my rgb image. Any help would be greatly appreciated!

Answer 1

[David Young]

JPEG images are read directly as rgb - so there's no map. So you don't need the call to ind2rgb (or the second result from imread). The reason the third dimension of cdata is 3 is that it is already rgb.

Answer 2

[Tessa]

I was afraid so. That probably means the method I'm trying to use is corrupt. It includes this line:

if (not (ismatrix(im)) || not (ndims (im) == 3))
      error ('Argument 1 (im) must be a RGB image')
end

Now, how I understand it, ismatrix(im) includes

if (not(ndims (im) == 2))
  ret = 0;
end

This means that my original error check will return an error in all cases right? Because ismatrix will return false on all rgb images?

[David Young]

The expression

(not (ismatrix(im)) || not (ndims (im) == 3))

is true for all values of im. It doesn't matter what im is, the function will always throw an error.

I guess you should probably just omit the first part of the test, so you have

if not(ndims(im) == 3)