Converting grayscale image to color

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Converting grayscale image to color - bwestoz - 02-04-2025

Win 10/GIMP 2.10.38

Converting grayscale image to color.

I am trying to work out a way to convert a grayscale image to color.

If I open a grayscale image and convert to RGB with Image>Mode RGB, the image does not behave like other RGB color images.

For example if I then choose Colors>Color Balance and move the sliders the image color does not change where as with other RGB images the image color changes if I do this.

I've tried simply creating a new (RGB) image and copying and pasting the grayscale image to the new image. If the new image has a white background this works but if I create a new image with a transparent background it doesn't. Why is this?

I notice that if I create an image with a white background the color channels seem as expected, ie Red Green and Blue but if I create an RGB image with a transparent background the color channels don't seem to have any color. Why is this?

Is there a way I can convert a grayscale image to RGB color so I can use the sliders in Image>Color Balance to change the color of an image but maintain a transparent background?

Thanks

RE: Converting grayscale image to color - Ofnuts - 02-04-2025

(02-04-2025, 12:29 AM)bwestoz Wrote: Win 10/GIMP 2.10.38

Converting grayscale image to color.

I am trying to work out a way to convert a grayscale image to color.

If I open a grayscale image and convert to RGB with Image>Mode RGB, the image does not behave like other RGB color images.

It should. Is the initial image grayscale in Gimp (title bar says "Grayscale" somewhere)? After Image > Mode > RGB the image should be converted to RGB mode (again, this should show in the title bar)

(02-04-2025, 12:29 AM)bwestoz Wrote: For example if I then choose Colors>Color Balance and move the sliders the image color does not change where as with other RGB images the image color changes if I do this.

I've tried simply creating a new (RGB) image and copying and pasting the grayscale image to the new image. If the new image has a white background this works but if I create a new image with a transparent background it doesn't. Why is this?

I notice that if I create an image with a white background the color channels seem as expected, ie Red Green and Blue but if I create an RGB image with a transparent background the color channels don't seem to have any color. Why is this?

In the Channels list the RGB color channels always appear as grayscale thumbnails of the channel so can you post a screenshot?

(02-04-2025, 12:29 AM)bwestoz Wrote: Is there a way I can convert a grayscale image to RGB color so I can use the sliders in Image>Color Balance to change the color of an image but maintain a transparent background?

Thanks

Image > Mode > RGB should do it. Can you attach the grayscale image here?

RE: Converting grayscale image to color - H.Seldon - 02-04-2025

If you want to apply color to a greyscale image, you might start with Colors > Desaturate > Sepia first.

RE: Converting grayscale image to color - bwestoz - 02-04-2025

(02-04-2025, 01:32 AM)Ofnuts Wrote:
(02-04-2025, 12:29 AM)bwestoz Wrote: Win 10/GIMP 2.10.38

Converting grayscale image to color.

I am trying to work out a way to convert a grayscale image to color.

If I open a grayscale image and convert to RGB with Image>Mode RGB, the image does not behave like other RGB color images.

It should. Is the initial image grayscale in Gimp (title bar says "Grayscale" somewhere)? After Image > Mode > RGB the image should be converted to RGB mode (again, this should show in the title bar)

(02-04-2025, 12:29 AM)bwestoz Wrote: For example if I then choose Colors>Color Balance and move the sliders the image color does not change where as with other RGB images the image color changes if I do this.

I've tried simply creating a new (RGB) image and copying and pasting the grayscale image to the new image. If the new image has a white background this works but if I create a new image with a transparent background it doesn't. Why is this?

I notice that if I create an image with a white background the color channels seem as expected, ie Red Green and Blue but if I create an RGB image with a transparent background the color channels don't seem to have any color. Why is this?

In the Channels list the RGB color channels always appear as grayscale thumbnails of the channel so can you post a screenshot?

(02-04-2025, 12:29 AM)bwestoz Wrote: Is there a way I can convert a grayscale image to RGB color so I can use the sliders in Image>Color Balance to change the color of an image but maintain a transparent background?

Thanks

Image > Mode > RGB should do it. Can you attach the grayscale image here?

Thanks for your reply. I've attached the image.

RE: Converting grayscale image to color - rich2005 - 02-04-2025

Nice frame. With images like that use the alpha-lock top right of the layers dock.

Put the image into RGB mode Image -> Mode -> RGB then enable the alpha lock. Up to you what you do then, bucket fill, all sorts. Remember to turn alpha-lock off when finished.

[attachment=13053]

50 second example: https://i.imgur.com/6x9Xe3T.mp4

EDIT: A couple of notes, Copy / Paste or Open as Layer the greyscale over a RGB image and the whole thing takes on RGB. The same is true in reverse a RGB image dropped in a greyscale image and the whole is GS.
You can add the frame over a RGB image (Image -> Open as Layers), size it up (if required) and then apply the alpha lock / recolour to the frame layer.

RE: Converting grayscale image to color - bwestoz - 02-06-2025

Hi Thanks for your reply and suggestions.

I tried;

1 Changing to RGB / locking the alpha layer

and

2 Creating a new image and importing that file as a layer.

and

3 Simply pasting into an RGB image.

I still cannot change the color of the frame with Colors>Color Balance and the sliders (Cyan, Magenta, Yellow).

It works if I paste it onto a white background but not if I put it on a transparent layer.

I don't know why. You seem to be able to do it.

I'm at a loss

Thanks anyway

RE: Converting grayscale image to color - rich2005 - 02-06-2025

Why fixated on using Color Balance ? You are trying to balance Black which has no color. Really that tool is meant for photographs.

You can use that tool if you pre-fill with some other color, I used a cyan-ish here.

[attachment=13070]

Better if you use some other tool, colorize is a safe choice.

RE: Converting grayscale image to color - bwestoz - 02-07-2025

Yes, Colorize seems to work once I got the hang of it.

Thank you

These grayscale images are ones I've downloaded from

https://publicdomainvectors.org/

by the way.

Thanks again Smile