Is it possible to have black and white and color image on same window by using opencv?

fraxel's answer has solved the problem with old cv interface. I would like to show it using cv2 interface, just to understand how this easy in new cv2 module. (May be it would be helpful for future visitors). Below is the code:

import cv2
import numpy as np

im = cv2.imread('kick.jpg')
img = cv2.imread('kick.jpg',0)

# Convert grayscale image to 3-channel image,so that they can be stacked together    
imgc = cv2.cvtColor(img,cv2.COLOR_GRAY2BGR)
both = np.hstack((im,imgc))

cv2.imshow('imgc',both)
cv2.waitKey(0)
cv2.destroyAllWindows()

And below is the output I got:

Yes it is, here is an example, expaination in the comments:

import cv
#open color and b/w images
im = cv.LoadImageM('1_tree_small.jpg')
im2 = cv.LoadImageM('1_tree_small.jpg',cv.CV_LOAD_IMAGE_GRAYSCALE)
#set up our output and b/w in rgb space arrays:
bw = cv.CreateImage((im.width,im.height), cv.IPL_DEPTH_8U, 3)
new = cv.CreateImage((im.width*2,im.height), cv.IPL_DEPTH_8U, 3)
#create a b/w image in rgb space
cv.Merge(im2, im2, im2, None, bw)
#set up and add the color image to the left half of our output image
cv.SetImageROI(new, (0,0,im.width,im.height))
cv.Add(new, im, new)
#set up and add the b/w image to the right half of output image
cv.SetImageROI(new, (im.width,0,im.width,im.height))
cv.Add(new, bw, new)
cv.ResetImageROI(new)
cv.ShowImage('double', new)
cv.SaveImage('double.jpg', new)
cv.WaitKey(0)

Its in python, but easy to convert to whatever..

Small improvement to the code with modern writing

concatenate

instead of

hstack

that is discontinued (stack can also be used)

import cv2
import numpy as np

im = cv2.imread('kick.jpg')
img = cv2.imread('kick.jpg',0)

# Convert grayscale image to 3-channel image,so that they can be stacked together    
imgc = cv2.cvtColor(img,cv2.COLOR_GRAY2BGR)
both = np.concatenate((im,imgc), axis=1)   #1 : horz, 0 : Vert. 

cv2.imshow('imgc',both)
cv2.waitKey(0)
cv2.destroyAllWindows()