ghostscript converts my pdf to cmyk but not really

Question

I run this command and the conversion is successful

    gs \                                                                                                                                      
       -o converted-to-cmky.pdf \
       -sDEVICE=pdfwrite \
       -sProcessColorModel=DeviceCMYK \
       -sColorConversionStrategy=CMYK \         
       -sColorConversionStrategyForImages=CMYK \
       ./original-srgb.pdf        

But then I run

identify -verbose ./converted-to-cmky.pdf

And it still reports 'Colorspace: sRGB'. Any idea of what could be causing this? Thank you.

Answer 1

Imagemagick identify is basically lying. It has no idea about individual objects in the PDF file. PDF can easily contain both CMYK and RGB objects, not to mention spot color plates etc., mixed all together.

Use either commercial Adobe Acrobat Pro preflight check to see the actual situation, or open the resulting PDF in Scribus and go to Edit-Colours and remove unused colours, to see if all colours in the PDF are actually CMYK or not. Probably they will be even though identify will think the PDF being RGB.