how to re-color some parts of a image ....

[saint_m]

hello everyone 

good day!

how to re-color some parts of a image 

which options do we have here

[rich2005]

(08-03-2025, 09:49 AM)saint_m Wrote: hello everyone 

good day!

how to re-color some parts of a image 

which options do we have here

You need to give details of the image.

Is it from an old monochrome photograph ? 
Is it a line drawing ?
Is it already colored, and you want to change some of the colours ?
..or..something else ?

[saint_m]

good day dear ritch

many thanks for the quick reply. - awesome. 

glad to hear from you

(08-03-2025, 09:49 AM)saint_m Wrote: hello everyone 

good day!

how to re-color some parts of a image 

which options do we have here

You need to give details of the image.

Is it from an old monochrome photograph ? 
Is it a line drawing ?
Is it already colored, and you want to change some of the colours ?
..or..something else ?

   




well - see an example what is meant - thie image shows a little visualized "network". - it consits of dots and links (connections or in other words - nodes)


what is aimed: 
 - this visualzid network should be visible on a background with a colorde color sheme. 
- therfore the here visible dots and lines (connections) should be re-colorized (to be visible on the gradient network) 

so we need to do several things

a. create a background with the color sheme (a gradient color-sheme)


see an example:; 

   
 
since this network should be shown up in white - (white dots and white lines) - all of the colors (in our little example-image) should be "re-colored" - to be finally visible as white 

b. working on the "network" . consisting of the dots and lines) exchange the colors everything that is black to wihte. (that will recolor the lines)

Look forard to hear from you

[rich2005]

(08-03-2025, 11:03 AM)saint_m Wrote: what is aimed: 
 - this visualzid network should be visible on a background with a colorde color sheme. 
- therfore the here visible dots and lines (connections) should be re-colorized (to be visible on the gradient network) 

so we need to do several things

a. create a background with the color sheme (a gradient color-sheme)

see an example:; 
 
since this network should be shown up in white - (white dots and white lines) - all of the colors (in our little example-image) should be "re-colored" - to be finally visible as white 

b. working on the "network" . consisting of the dots and lines) exchange the colors everything that is black to wihte. (that will recolor the lines)

Look forard to hear from you

You can try this:

   

(1) Layer -> Colors -> Color-to-Alpha  Leave default white for the white background but reduce Opacity THreshold to 0.7 - 0.8
(2) Colors -> Desaturate -> Mono Mixer with all channels to minimum -5.000 Gives a black image

   

(3) Colors -> Invert  for a white image.
(4) If you want more solid color - Duplicate layer, set the layer mode to  Grain Merge.

[saint_m]

hiello dear Rick2005

note: curently short of time - but iwll answer more thoughroughly later the day

many thanks for the quick answer -and for sharng your ideas and knowledge

awesome - just outstanding.: All looks so great

greetings

[saint_m]

again dear Rich2005


i am really happe to be part of this forum. Your ideas and your support are really great.   Now i am trying to recap and to undersrtannd each single step you made. Here my first try to work on the "soluion" here. 
 

see what i have understood in your example "


 hmmm - i think that i can use th Color to Alpha filter in GIMP

this "color To alpha " can be found in the "Color"-Menu.  

Well Rich2005 i have addes another example of and image here... 

see the example: 


   


what is aimed here: i  want to mount this image to a certain background - a background with a gradient color sheme. 

AFAIK ::  this should converts a selected color in my image to transparency. This filter - note it is located under the "Colors" menu and well i think it might be useful for removing a specific color: In my case i want to remove the green.

color of the dots - i want to make them all black.

well i think this should be possible, (( while preserving anti-aliasing and blending effects.))

Here's my first step:

well i think i could do this with the help of an alpha channel. ... but how !?

note: at the end the dottted netwok should be "mounted on a "gradient background". - and then the all the network (dots and lines ) should get white ....

i guess that we can do this step with the so called "inversion".

.but at the moment not all steps are clear to me! 

Sorry for all my noob-questions - i am trying to go ahead - but my steps are very verry small 

[rich2005]

(08-05-2025, 11:04 PM)saint_m Wrote: ......hmmm - i think that i can use th Color to Alpha filter in GIMP

this "color To alpha " can be found in the "Color"-Menu. 

Use Color-to-Alpha (C2A) to remove a single color background when possible. It keeps semi-transparency including the edge anti-aliasing. For your image, some color is also removed. Fixed to a certain amount using C2A opacity slider but this can also removes anti-aliasing. Up to the user to decide what is acceptable.

Quote:....i have addes another example of and image here... 
this should converts a selected color in my image to transparency. This filter - note it is located under the "Colors" menu and well i think it might be useful for removing a specific color: In my case i want to remove the green color of the dots - i want to make them all black.

well i think this should be possible, (( while preserving anti-aliasing and blending effects.))

An alternative way because the dots in the image are small and lose that important anti-aliasing. Using a trick to remove the color background and restore ant-aliasing.

about 2 minutes https://i.imgur.com/WJMJEh9.mp4

What it shows:
Check the alpha-channel Layer -> Transparency - OK it has one
The trick: Scale the layer up 200% Image -> Scale image Use Interpolation = NoHalo
Color Select the background and Edit -> Cut to delete it
Select -> Invert and click on a dot to select.
Fill the selection with color (black)
Select -> None
The trick: Scale the image down to 50% back to original size, the interpolation (NoHalo) adds anti-aliasing.

Save this image and add to your background File -> Open as Layers. Merge down as required.

[saint_m]

hello dear Rich2005

first of all: many many thanks for the quick reply and for your incredible help. This is really awesome - and i learn alot.

btw: the videoclip is very impressive - and shows many important steps.


especially the step: "select the color (of the background)" and "erase it!" - this is pretty important!

thank you



What it shows:

Quote:Check the alpha-channel Layer -> Transparency - OK it has one
The trick: Scale the layer up 200% Image -> Scale image Use Interpolation = NoHalo
Color Select the background and Edit -> Cut to delete it
Select -> Invert and click on a dot to select.
Fill the selection with color (black)
Select -> None
The trick: Scale the image down to 50% back to original size, the interpolation (NoHalo) adds anti-aliasing.

on a sidenote: btw: plz plz plz. keep this video clip alive:

https://imgur.com/WJMJEh9

i have had situations wehere some guys on the net produced helperclips (videoclips) that were very helpful - but they vanished one or two days after publishing date - what a pidy.




dear Rich 2005 thank you for all your continued help!! You are a Gimp-Hero!!



i also will have a closer look at the c2a things

Quote: Use Color-to-Alpha (C2A) to remove a single color background when possible. It keeps semi-transparency including the edge anti-aliasing. For your image, some color is also removed. Fixed to a certain amount using C2A opacity slider but this can also removes anti-aliasing. Up to the user to decide what is acceptable.

thanks for all - keep up your superb work here..

Greetings