Need help with adding color to a black and white jpg of Io

[alegator]

This is the situation:
I have two cylindrical maps of Io, one is a low resolution color image, the other one is a high resolution one. I resized the high resolution one to the size of the lowres one, but before using it in Celestia I would like to colorize it. To this effect I thought about importing the color (channels?) of the lowres pic into the hires one. Is this possible? If so, what are the step by step instructions to do so with Photoshop?
Thnaks.

[jim]

Ok , a short description:

Open both maps in Photoshop, resize (enlarge) the lowres color map to size of the large one. Now change the picture mode for both maps to LAB-Color. Copy the a and b channels from the color map in the a and b channels of the high resolution map (CTRL+A->CTRL+C->CTRL+V, Channer per Channel). Finely, change the color mode back to RGB and save the file.

I think this should work. I can't give a step by step instruktion please check Photoshop-Help.

[alegator]

Jim,
Thanks for your info. I was able to:
1) Open both maps in Photoshop
2) resize (enlarge) the lowres color map to size of the large one
3) change the picture mode for both maps to LAB-Color

After this step Photoshop 7 will display for each image 4 channels:
- Lab
- Lightness
- Channel a
- Channel b
(channels a and b are empty (all gray) in the black and white pic)
After this point I didn't know how to copy the a and b channels of the color pic into the black and white hires one. I tried "Duplicating" the channels from the color pic into the black and white, but when going back to RGB mode I don't get any color pic.
Any idea?
Thanks again.

[alegator]

Ok, I think I finally got it. Instead of duplicating the channels from the color pic into the black and white what I did was create a third new pic (empty) and duplicate channels a and b from the color pic and the Lightness channel from the black and white and color shows up even in Lab mode, I anyways turned it into RGB mode and saved it as a jpg.
I included this 8192x4096 color pic of Io in Celestia and it displays beautifully.
Thanks.