tif, transparency and CMYK

[pieterG]

I'm new at IM but very impressed by what's possible.

What I cannot find is the following.... I've got a TIF-image picture with a transparent background in colorspace RGB
I want it in colorspace CMYK, with the transparency kept of course. It just doesn't work. It stays RGB.

Only if I take the original as a RGB JPG image, the background is white now, it converts to a CMYK TIF image,

Trying the following afterwards;

convert imageCMYK.tif -transparent white imageCMYKtransp.tif

It returned the image to the RGB colorspace again...

Anyone on how to convert my RGB tifs to CMYK tifs preserving the transparancy?

[magick]

ImageMagick supports CMYKA but some of the options require the RGB colorspace such as -draw. However, -transparent does not. Note you will need to specify the transparent color in CMYK. Instead of -transparent white use -transparent 'cmyk(?,?,?,?)' where ? is whatever 0-255 value is needed to specify white. If that fails, make sure you have a current release of ImageMagick and try again.

[pieterG]

I've tried again.

Even with the latest version (ImageMagick-6.4.7-10-Q16-windows-dll.exe, tried on XP pro and VISTA home premium) I've got no success.

All my steps in a row;

I have got a picture. imageRGB.tif the background is transparent, colorspace is RGB. I want the colorspace to be CMYK.

Code: Select all

convert imageRGB.tif -colorspace CMYK imageCMYK.tif 

does not work

Code: Select all

convert imageRGB.jpg -colorspace CMYK imageCMYK.tif 

does work but then I need to add the transparency afterwards as .jpg does not allow transparency. After that I tried

Code: Select all

convert imageCMYK.tif -transparent "cmyk(0,0,0,0)" imageCMYKwithTransparency.tif 

This does not work either. It just returns this message "convert: Too many color components: 5, max 4. `JPEGLib' @ tiff.c/TIFFErrors/324."

Why can't is convert a RGB tif straight to a CMYK tif? Is this a bug? Am I missing something?