Coloring one image with another

[JavaTyper]

Godday,
if you have two images of the same object (let's say scans, to evade some of the complexities of photography), where
image A has captured the colors correctly, but is otherwise undesirable (blurry, low-resolved or the likes) and
image B is adequate in detail but lacks color (greyscale).

Question:
Can i use image A to paint image B without degrading the latter,
and what is this task called in terms of digital imaging?

[Ofnuts]

Yes, if you can make the two images overlap, then you can put the color image in a layer above the grayscale image and set it to Color mode (Gimp 2.8) or LCH Color or HSL Color (Gimp 2.10).

This works because the perceived sharpness of an image is more related to the luminosity than to the color. This is precisely the "chroma sub-sampling" done in the JPEG format. In JPEG, your image is stored as 3 images, a grayscale image that has the definition of your source image, and two color channel images. These images can be kept at the full definition ("full chroma"), but can also be reduced ( half-width, half-height (chroma halved) or both (chroma quartered). Decoding is then the process above, using a low definition color image to color a high-definition greyscale image.

The chroma subsampling is very important in JPEG, just using the quartered chroma divides the final size by 2 (full chrorma is 1+1+1=3, quartered chroma is 1+.25+.25=1.5

[rich2005]

Another way:

The built-in Gimp tool is sample colorise Colors -> Map -> Sample Colorize see: https://docs.gimp.org/2.10/en/plug-in-sa...orize.html

might work like this: https://i.imgur.com/Fy7xdI5.mp4

All depends on the image(s) There is a Gimp plugin gimp_gmic_qt http://www.gmic.eu which has some transfer colour filters which can be effective, again, depends on images.

[JavaTyper]

(08-30-2020, 02:41 PM)Ofnuts Wrote: Yes, if you can[...]

Many thanks, this is exactly what i was looking for.

And thank you rich2005 for the alternative way.