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I am looking to print an image with a white layer behind the color image. The image is of a face with the background in transparent. When it get's printed, it goes on a dark wall and therefore I wish to lay down white prior to the color layer. Apparently this can be done in Photoshop using a spot channel. When I google 'spot channel GIMP' I get info on channels but nothing specific. I am a rookie with GIMP, but really want to give it a chance. Any help would be appreciated. All exports have todate been Tiff files and the transparency begins printing in black, with no white layer behind. In the image below, the white wall area of the wall is the transparent region.
Again, the idea is The Wall Printer lays down an area = to the facial region in white and prints the actual facial image in color over top the white, because it's going onto a dark wall color. This can be done with PS, i'm just trying to prove it can happen with GIMP as well. Any help would be greatly appreciated.enter image description here

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  • Have you checked with the printer if it's actually possible to print white? This is not just a digital issue, but also a physical one.
    – Wolff
    Mar 26, 2021 at 17:07
  • I don't believe GIMP supports CMYK, at least not natively. You sort of need CMYK support for spot colors. But that doesn't necessarily mean you can't simply create an underlying shape and print it first, then print the rest of the piece. It doesn't have to be white.. it can be any color on screen.. merely tell the print provider to use white ink (see Wolff's comment though).
    – Scott
    Mar 26, 2021 at 18:04
  • The printer does print white, yes. I'll try to create a copy of the user video for photoshop if I can and provide a link.
    – Faron Fowler
    Mar 29, 2021 at 1:44
  • You make a good point Scott, but the entire idea is to let the printer do the work all in one shot, rather than performing two print processes and having to accurately line up the the secondary application to overlay the 1st one.
    – Faron Fowler
    Mar 29, 2021 at 1:46
  • It might have to be that I acquire a license for PS in order to print images in this manner.
    – Faron Fowler
    Mar 29, 2021 at 2:19

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GIMP has no spot colour channel support, nor does it support CMYK images used for print separations. To be honest, GIMP is not ideal for print work. Also note that CMYK printing doesn't involve the use of white Ink. So you'd need to check that requirement with your print supplier to find out what's possible. It would have to be created in such a way that a white separation can be done, assuming your printer is capable of printing it.

It might be possible to improvise a bit however.

You could fill a selection white under your transparent image layer, and duplicate that layer invert it, and merge it with a white layer under that to give you a usable white separation which your printer will need.

Here's an example

enter image description here

As for the CMYK problem, you could open the GIMP XCF file in Krita (which is also free and open source) and convert it to CMYK, since Krita does support CMYK. Then assuming your printer has Photoshop, you could export it as a PSD (Photoshop Document). The layers will be preserved, and your printer will have access to the white separation layer.

Another possibility would be to export the finished GIMP work as a PSD (Photoshop Document) directly. Again, if your printer has Photoshop they could easily convert it to CMYK for you. It only takes a second.

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  • I did create the white layer, but did not create the white separation layer (inverted) as you are demonstrating above. I'm going to give that a go and attempt to use Krita as you suggested to convert to CMYK. We are using Maintop software to print the file to a .prn file before printing, as long as Krita can preserve the layers exporting to a file that Maintop recognizes (usually we use a tif, jpg), in theory it could work. Will update. Thanks for the tip Billy.
    – Faron Fowler
    Mar 29, 2021 at 13:55
  • Well, I tried your suggestion Billy. Unfortunately I get a dialogue box in Krita that says: "Could not open file: [path][name].xcf" "This XCF file is too new; Krita cannot support XCF files written by GIMP 2.9 or newer.:
    – Faron Fowler
    Mar 29, 2021 at 14:33
  • @FaronFowler Then instead try the second method. Export as PSD directly from GIMP. Krita can also open PSDs. Layers should be preserved. Then you could convert to CMYK in Krita. I've no idea what Maintop is. But Krita does support CMYK TIFFs, although I'm not sure if it supports TIFFs with layers. You could perhaps output a separate TIFF for the white layer, and a CMYK TIFF for the coloured image.
    – Billy Kerr
    Mar 29, 2021 at 15:30
  • update: I downloaded an older version of GIMP to my laptop 2.8.22 and reworked the image as per the layering discussed.. The xcf does open in Krita. I exported 3 images from Krita after converting the image to CYMK non flattened.. .a tif, a jpg, and a psd.
    – Faron Fowler
    Mar 29, 2021 at 18:35
  • Upon loading those images in Maintop and printing to the .prn file, I am finding that the tiff files generate an error. The psd and jpg file do print... The jpg printed with full transparency on the outside as expected and the image centered looks good as well. The initial test was very small however and not on the darkest backdrop so I am having trouble deciphering whether or not the white layer is being printed. I will test again on a darker surface...likely black... to see if I can realize the same image in the same manner on a darker backing (i should see the white layer more clearly).
    – Faron Fowler
    Mar 29, 2021 at 18:36

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