changing an image to rgb format

hi every body

I have an image stored in png format,its size is 256*256 but I need to have the image in size 256*256*3 which format should I use to store it? is there any way that I can do it in matlab?

Answer 1

[Matt Fig]

A png is already 3D. I have an image named IMG.png in my directory. Now look:

>> X = imread('IMG.png');
>> whos
   Name         Size                   Bytes  Class     Attributes

     X         2304x2857x3            19747584  uint8