Checking if a PDF is in CMYK color space under Linux

Photo credits: Alexander Grey:

Typical instructions to check if a PDF file is in the CMYK color space, require Adobe Acrobat to be installed. The Adobe suite isn’t available under Linux, and more importantly, it’s not Free Software. At first glance, it seems hard to figure out if a document is in the CMYK-color space.

Why CMYK is relevant

CMYK stands for “Cyan-Magenta-Yellow-blacK (Key)” and represents the four basic ink colors that are used for full color printing. While print (on paper or materials) is done by spitting ink on materials, your screen is creating colors using light rays. Here, the colors are red, green and blue (hence RGB). Because this is a completely different way of creating colors, there is no 1-on-1 translation possible between “standard RGB” to “standard CMYK”. The most important reason is because both displays and printers (and materials) influence how colors appear in a big way.

So if you want to reliably know what something will look like, you’ll have to tell the printer exactly how much ink of every color to spit on the paper. Typical print stores will supply you with a print profile to adhere to (basically telling the computer what RGB colors would look like when printed).

Bottom line: the printing company will need to receive a CMYK-based file for print.

Use Scribus

Scribus is a desktop publishing application that allows you to use different color spaces. It also perfectly opens PDF documents.

When opening a PDF file, you can choose the “Colors and Fills” item in the Edit menu:

After selecting that option, the dialog menu appears, showing an overview of the colors. You can recognize CMYK-colors through their 4 squares CMYK icon. RGB-colors appear with a red, green and blue striped icon. Using the “Edit” button, you can even convert and RGB color to CMYK (based on the color profiles configured in the settings).

Other options?

I’m still looking for easy command-line ways to determine the color space of a document. Please place your suggestions in the comments.






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