In GIMP, how do I use an image as a color reference to colorize a black-and-white photo?

Question

Let's say I have created a layer on a black-and-white image with a layer mask to colorize some parts (for example skin). I am able to change this with Colorize and change to any color.

But how do I use another image of color of skin (as reference)? Is there a way to select a portion of skin on the color image and apply it to my layer with a mask that I painted so that my masked layer looks just like the skin color of the color image (the reference image)?

I am trying to follow this tutorial, but instead of colorize I want to select a colored image (or portion of colored image) as a color reference. That way it's more realistic.

Or does there exist a GIMP plug-in that will allow me to change dark grey values to take on darker tones of a selected area of colored image and brighter grey values to take on tones brighter tones of a selected area of a colored image?

I wanted to try colorizing a black-and-white photo after seeing this post.

Answer 1

I think I found a way to do this in GIMP version 2.8.6. Here are the steps:

1) I have created a layer (copy of black and white image with a mask that selects only the skin) like below.

2) I then have another image (colored image of skin):

3) I then use the free-hand select tool to select a portion of skin (of the colored image) which includes some skin highlights, mid-tones, and shadows of skin.

4) I then go back to my black and white images (select the layer with skin) and then select menu item "Colors" -> "Map" -> "Sample Colorize"..., and this window appears

5) I then select the "Sample: drop down" and select the colored image of skin that had my free-hand selection of different shades of skin, then select "Destination: drop down" and select my skin layer. I then clicked on "Get Sample Colors", played around with other controls a bit to see what they do, but I wasn't too sure of what they do, the default seems to be fine. Then click on "Apply" (this applies to the actual layer) so if you have this window in the way, drag and move it to the side to see your layer showing what apply does. Click "Close" when done. I ended up with the below.

I left the mode of the layer as "Normal"; it looked good to me. You can try setting Mode of layer to "Color" or others to see if it gives different results.

I have to say this is the best skin colorize I have done. It's way better than selecting a single color like "Colorize".

Here's an image that I colorize using a sample of gold:

Here's another that I colorized from a black-and-white photo of Abraham Lincoln:

Here's another Audrey Hepburn one colorized from a black and white photo.

If you colorize some black and white photos, please share by commenting below. I'd love to see them :)