I've exported a white-and-transparent, non antialiased PNG image from Inkscape (development version).
Then I opened it with Krita 3.3.2 - so far, so good.

Then I converted it to CMYK color space with a specific icc profile (ISO Coated v2 300% (ECI)).

Then I tried to save as tiff image, but the option to preserve transparency is greyed out.

Link to screenshot: http://i.imgur.com/HwX10Oo.png

When I save, then open the tiff in Krita, I get a black-and-white image.

Then I can try the same again - selecting the black by color, deleting the selection, saving, and get the same result (I thought it could have to do with some property of the original png's transparency).

Can someone please explain how this is supposed to work?

I need a CMYK tiff image with transparency for my printer, who is supposed to print white color on a dark T-shirt.

I can share the png, but the tiff file is just too large with its 1200 dpi (1 GB).

Additional: When I try to convert an RGB tiff file that has been exported by gimp to CMYK in Krita, this seems to never end and at some point blocks mouse usage and display - I can't even get a console to open to stop it. Had to do a hard reset...

This is on Linux Mint 18.3.

The original source of your .png image doesn't matter because if krita shows transparency then the image has transparency.

I have the krita 4.1.1 Linux appimage and I can convert from RGB with transparency to CMYK with transparency and then Save As a .tif file with transparency as follows:

When the options sub-window for saving as .tif comes up, the 'Store alpha channel' tick box is greyed out, but if you tick the 'Flatten the image' box then the alpha channel box becomes active. Then it saves with transparency as shown by opening the .tif file in krita and in other image applications.

I've no idea why 'Flatten the image' should work on a single layer image but different image file formats and transparency is a complicated area.

I'd suggest that you download the 4.1.1 Linux appimage and use that instead of your current 3.3.2 version.

As a matter of interest, why are you using 1200 dpi for printing on a T-shirt? The material of a T-shirt would not be capable of holding that resolution of printed ink and a 300 dpi resolution would be more than adequate. (It may be that your printing company does that as standard, so fair enough.)

"Additional: When I try to convert an RGB tiff file that has been exported by gimp to CMYK in Krita ..."

I just did this with no problems using GIMP 2.8 and krita 4.1.1. However, I used one of the built-in CMYK colour profiles. I believe you're using an imported colour profile so you might want to try a built-in profile to see if that has any effect (even though it shouldn't).

Thank you, @ahabgreybeard. I didn't try again with the older Krita version (as you can see - or maybe not, as it's in German - the flatten image option was selected in my screenshot, but the other option was still greyed out), and used the AppImage file, as suggested.

This one showed a couple of other (minor) bugs, but the conversion seems to have worked well.

(e.g. when selecting a color profile by adding it from an outside directory, the newly selected profile is added to the dropdown list, but it's not selected; and the mouse cursor vanishing inside the Krita window, but being available on other parts of the monitor, as soon as Krita is busy doing calculations.)

I agree, 1200 dpi is overkill They want 'at least 600dpi', and I always veer to the safe side. I'd have preferred giving them a vector file, but they claim that 'pdf does not support transparency' and last year, seemed to be unable to handle svg or eps... or even RGB tiff files that had a transparent background for me in gimp So this year, I'm trying with Krita and a real CMYK tiff. Let's see what they'll produce...

I'll do the test after I post this, just in case I need to reboot.

Update: in 4.1.1, it worked without freezing (and it generally seems about twice as fast dealing with these large images)

Thanks again! I'll send it to the online printer tomorrow, and I hope I'll hear back from them soon... Better first make a test shirt, there's still some time.

Thanks again, it worked:



In case the image isn't visible:
https://twitter.com/kielux/status/1033701154000125953