Compose CMYK from separated layers after editing in Krita

Using Krita 2.9, Linux or Windows 8:

I open a flat RGB image in Krita and change its color space to CMYK using SWOP profile. Then I separate the image into its C, M, Y, and K components. At this point, I have 5 layers, including the original un-separated CMYK image.

I edit one of the layers. So far, so good.

Now, I wish to re-compose the image. Instead of separated layers, I want the image to be unified, in a way that incorporates the edits I made to one of the separated layers.

I cannot find how to re-compose the layers in Krita. Can this be done? It does not matter if I first delete the original layer, or not.

Note that the original image is not updated to reflect any change to a component layer. And, exporting to various formats (PDF, TIF, JPG) merely reduces everything to the topmost visible layer.

By comparison: The infamous separate+ plugin for GIMP will not only separate to CMYK layers, it will re-compose them with edits in effect.

EDIT: I discovered that GraphicsMagick can help me (outside of Krita). It can separate the CMYK image into its four channels as separate greyscale images. I can edit the separated images as greyscale, then re-assemble them to a single CMYK image, again using GraphicsMagick. The procedure is described on their website.

Answer

At request of @gburning, I answer it myself:

Once I have the CMYK image, I finish it outside of Krita. I use GraphicsMagick (maybe ImageMagick would work too). The code is on the GraphicsMagick web site:

http://www.graphicsmagick.org/FAQ.html#how-can-i-extract-and-combine-cmyk-channels-in-a-cmyk-image

Works great. The reason I use it: I wish to ensure that a portion of the image (barcode), which should be pure black, really is pure K rather than rich black with some CMY. So I separate the image into 4 grayscale images that can be edited separately in any program, since they are free of color. Wash away any undesired CMY, then re-assemble to CMYK.

Attribution
Source : Link , Question Author : RobtA , Answer Author : RobtA

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