JPEG to CMYK conversion issue?

Discussions on NConvert - the command line tool for image conversion and manipulation

Moderators: XnTriq, xnview

Post Reply
zazarb
Posts: 2
Joined: Thu Apr 16, 2015 6:46 am

JPEG to CMYK conversion issue?

Post by zazarb » Thu Apr 16, 2015 7:17 am

Hello,

Sorry if the question is obvious but I am new to CMYK conversion.

I have just tried to use NConvert to convert RGB Jpeg files to CMYK jpeg files, with a 300 dpi resolution (the original images have a 72dpi resolution):
nconvert -o output_file -out jpeg -dpi 300 -cmyk_space *.*

This command fails because my resulting jpeg images have a 72 resolution dpi (i.e. the resolution is not set to 300 dpi during the conversion)

When I do the exact same thing, but I convert the RGB Jpeg files to CMYK tiff or pdf files instead, everything works well (i.e. my result images have a 300 dpi resolution)
nconvert -o output_file -out tiff -dpi 300 -cmyk_space *.*

I have been trying to understand why it works with pdf/tiff format but not Jpeg format, can somebody explain this to me?

Thanks for your help

zazarb
Posts: 2
Joined: Thu Apr 16, 2015 6:46 am

Re: JPEG to CMYK conversion issue?

Post by zazarb » Thu Apr 16, 2015 11:27 am

[update] Actually the conversion to JPEG => CMYK pdf with 300 DPI also fails. I only succeed in gettying CMYK color space + 300 dpi by converting to TIFF
Thanks

User avatar
xnview
Author of XnView
Posts: 31891
Joined: Mon Oct 13, 2003 7:31 am
Location: France
Contact:

Re: JPEG to CMYK conversion issue?

Post by xnview » Thu Apr 16, 2015 2:26 pm

-dpi is only used for pdf, if you want to resize your picture use

Code: Select all

-resize
Pierre.

Koniec12
Posts: 3
Joined: Tue Jun 02, 2015 11:16 am

Re: JPEG to CMYK conversion issue?

Post by Koniec12 » Tue Jun 02, 2015 11:29 am

DPI is used generally for graphics not only pdf

Post Reply