How can I subtract data of an Image keeping the original image and not just a canal?

I need to subtract data of a whole RGB image. Imsubtract works only for a canal. Or, is there a function that can use merging the canals after the subtraction?.

Answer 1

[Angela Blanco]

I found the comand Icat= cat(3, I, I, I); very easy. Thanks

Answer 2

[Image Analyst]

You can just subtract them directly. If they are uint8, cast to single so that you don't clip negative values.

diffImage = single(rgbImage1) - single(rgbImage2);