Color Separation?

[Frankwpb1970]

Not sure if this is the correct forum, I am trying to learn how to do color separation in GIMP.

If anyone is kinf enough to explain the process I would be greatly appreciative.

[rich2005]

Do you require a cmyk image file - a jpeg or a psd There is a plugin called Cyan which is useful. there is an example here: https://www.gimp-forum.net/Thread-gimp-2...8#pid30238

Gimp is a RBG editor and all editing is RGB.
You can separate a rgb image into its c-m-y-k equivalent layers using Colors -> Components -> Decompose and choose CMYK {or RGB if that is what you want) from the drop down list.
That gives you greyscale images which are the masks of the separated colors.

It is a big subject and you should start with general concepts such as https://www.lifewire.com/color-separation-1697622
As you see, it is mostly a PhotoShop subject.

Edit: Just looking at your other posts: Is this for screen printing ? Some software mentioned here https://silverbobbin.com/color-separatio...-printing/

I can think of ways in Gimp but how many colours are you considering? Each colour requires its own black & white mask.

[Frankwpb1970]

(07-14-2022, 04:39 PM)rich2005 Wrote: Do you require a cmyk image file - a jpeg or a psd  There is a plugin called Cyan which is useful. there is an example here: https://www.gimp-forum.net/Thread-gimp-2...8#pid30238

Gimp is a RBG editor and all editing is RGB.
You can separate a rgb image into its c-m-y-k equivalent layers using Colors -> Components -> Decompose and choose CMYK {or RGB if that is what you want) from the drop down list.
That gives you greyscale images which are the masks of the separated colors.

It is a big subject and you should start with general concepts such as https://www.lifewire.com/color-separation-1697622
As you see, it is mostly a PhotoShop subject.

Edit: Just looking at your other posts: Is this for screen printing ? Some software mentioned here https://silverbobbin.com/color-separatio...-printing/

I can think of ways in Gimp but how many colors are you considering? Each color requires its own black & white mask.

Thanks for the reply, I would like to know both RGB and CMYK techniques. 
Im interested in making tshirts and want to use photo images to print on the shirts so if Im not doing black or white ink, I want to be abl to separate the colors and multicolor print.

[Frankwpb1970]

(07-14-2022, 08:28 PM)Frankwpb1970 Wrote:

(07-14-2022, 04:39 PM)rich2005 Wrote: Do you require a cmyk image file - a jpeg or a psd  There is a plugin called Cyan which is useful. there is an example here: https://www.gimp-forum.net/Thread-gimp-2...8#pid30238

Gimp is a RBG editor and all editing is RGB.
You can separate a rgb image into its c-m-y-k equivalent layers using Colors -> Components -> Decompose and choose CMYK {or RGB if that is what you want) from the drop down list.
That gives you greyscale images which are the masks of the separated colors.

It is a big subject and you should start with general concepts such as https://www.lifewire.com/color-separation-1697622
As you see, it is mostly a PhotoShop subject.

Edit: Just looking at your other posts: Is this for screen printing ? Some software mentioned here https://silverbobbin.com/color-separatio...-printing/

I can think of ways in Gimp but how many colors are you considering? Each color requires its own black & white mask.

Thanks for the reply, I would like to know both RGB and CMYK techniques. 
Im interested in making tshirts and want to use photo images to print on the shirts so if Im not doing black or white ink, I want to be able to separate the colors and multicolor print.

yes this is for screen printing

[zodiakteez]

(07-14-2022, 08:28 PM)Frankwpb1970 Wrote:

(07-14-2022, 04:39 PM)rich2005 Wrote: Do you require a cmyk image file - a jpeg or a psd  There is a plugin called Cyan which is useful. there is an example here: https://www.gimp-forum.net/Thread-gimp-2...8#pid30238

Gimp is a RBG editor and all editing is RGB.
You can separate a rgb image into its c-m-y-k equivalent layers using Colors -> Components -> Decompose and choose CMYK {or RGB if that is what you want) from the drop down list.
That gives you greyscale images which are the masks of the separated colors.

Are there others steps after this to make the CMYK separations ready for printing?( I did this and it was difficult to tell if the colors are actually separated...attachment

Edit: Just looking at your other posts: Is this for screen printing ? Some software mentioned here https://silverbobbin.com/color-separation-software-for-screen-printing/

What is your opinion of Ink Seps compared to GIMP?

Thank You for your help.

[rich2005]

I do not think screenprinting is the correct process for photographs. The CMYK greyscale separations are used with a different process, offset printing. where the colours combine. 

This is an example using CMYK, to get skin tones, half toned, and an additional technique with the layers at different angles. Look at the bottom image.  This is using metal plates, not masks, for the  offset printing. 

   

Maybe you can get that with traditional screenprinting. The half toning is very fine.  All you can do is try.  If your wrestler photo is a failure, think of other ways to enhance the image. Lots on the internet when you search. This one https://www.youtube.com/watch?v=L0NZBiUWAE4 correctly points out you are stuck with 3 or 4 colours so use them but as a design.

I advise a more screenprinting specific forum. You might already have tried. Some links here:  https://blog.feedspot.com/screen_printing_forums/

[rich2005]

Cobbled this together, It might work, all depends on materials.

https://youtu.be/T0ZiSgcojIA about 6 minutes. You could try a single layer on paper to see if the resolution of the dots holds.

Never going to be wonderful. If you print on a coloured material you need an extra layer first to provide a white base.

[zodiakteez]

(07-17-2022, 02:49 PM)rich2005 Wrote: Cobbled this together, It might work, all depends on materials.

https://youtu.be/T0ZiSgcojIA  about 6 minutes. You could try a single  layer on paper to see if the resolution of the dots holds.

Never going to be wonderful. If you print on a coloured material you need an extra layer first to provide a white base.

Thank you very much for the tutorial, sorry for late reply I have some health issues I deal with and I have been down for the last few days.

I followed your tutorial however I believe I missed something I will attach an image it seems I didn't set the transparency or something, are you able to see my mistake in the image?

I cant express enough how grateful I am for you taking the time to help me with this.

[rich2005]

Not a tutorial just a possibility: For the screenprint masks; step-by-step it is

Colors > Components > Decompose (to CMYK) That gives a new greyscale image so..
Image > Mode > RGB
For each layer in turn

•     Colors > Invert
  
•     Filters > Distorts > Newsprint (with settings as video varying the angle)
  
•     Colors > Threshold
  

   
For the fake "What it might look like printed"
Take the above (black figure on white) and for each layer

•    Colors > Color-to-alpha default is white.
  
•    Alpha lock on (the right icon top of the layers dock)
  
•    Fill with the appropriate color Cyan - Magenta - Yellow
  

Make a new canvas and overlay those same as you would with a physical screenprint.

If you are going to screenprint on colored cloth then you need an extra mask for a white base.

I do not think screenprinting is the method for photographs, Make your photo into some sort of abstract design. Think Andy Warhol paintings or Obama Hope poster.

[Frankwpb1970]

(07-19-2022, 03:23 PM)rich2005 Wrote: Not a tutorial just a possibility: For the screenprint masks; step-by-step it is

Colors > Components > Decompose (to CMYK) That gives a new greyscale image so..
Image > Mode > RGB
For each layer in turn

•     Colors > Invert
  
•     Filters > Distorts > Newsprint (with settings as video varying the angle)
  
•     Colors > Threshold
  

   
For the fake "What it might look like printed"
Take the above (black figure on white) and for each layer

•    Colors > Color-to-alpha default is white.
  
•    Alpha lock on (the right icon top of the layers dock)
  
•    Fill with the appropriate color Cyan - Magenta - Yellow
  

Make a new canvas and overlay those same as you would with a physical screenprint.

If you are going to screenprint on colored cloth then you need an extra mask for a white base.

I do not think screenprinting is the method for photographs, Make your photo into some sort of abstract design. Think Andy Warhol paintings or Obama Hope poster.

might converting the photo image into a cartoon like image be what you are suggesting?

Im at work I will follow those steps I understand you said its a possibility, its very much what I was trying to achieve so I again am thankful for your help.
Should transparency be on at any point?