imregister without converting to gray scale?!

I wonder if there is away to perform image registration without converting the image to gray scale first? I mean without (rgb2gray). Because I'm getting error "The value of 'MovingImage' is invalid. All dimensions of the moving image should be greater than 4." when I use imregister without converting to gray scale. Is there anything I might loose when I register two images after converting them to gray? My apology for asking many questions, but I'm new to Matlab world :) I appreciate your assistance. Regads, Yasser

Answer 1

[Image Analyst]

The images must be 2-D grayscale images or 3-D volumetric images according to the help. To do a color image you'd have to convert it to gray scale and get the transform, then split up the RGB image into separate color channels, and then use the transform on the individual color channels and then put them back together as an RGB image with cat(3,r,g,b).

[Yasser ALGhamdi]

Greetings, "split up the RGB image into separate color channels, and then use the transform on the individual color channels and then put them back together as an RGB image with cat(3,r,g,b)." Can you share with me any example how to do that, it seems a very good approach though a bit complicated! I mean splitting+transform+combining back... Thanks in advance!