make gray to color

HELLO, How can i make gray pixels to color pixels among gray scale's pixels? you can see my goal in: http://i39.tinypic.com/20rwlr7.png

I have two image(both gray) and i want to see one(color) in other(gray).

Thanks in advance

Answer 1

[Image Analyst]

Have you tried just assigning non-zero pixels to the other image

nonZeroPixels = image1 > 0;
image2(nonZeroPixels) = image1(nonZeroPixels);

If that's not what you want, then explain better.

Answer 2

[Walter Roberson]

Put the two images in the same position, with the color image on top, and in the color image set the AlphaData to 1 where the color should be used and set it to 0 where the image underneath should be used.

Note: this will require using the OpenGL renderer.