Invert colours in PDF files

Today I faced to following problem.

I wanted to print an ugly presentation which was stored in a PDF file. And I say ugly because the background was bright blue and the font of the text, yellow!

Printing this beauty in a printer will definitely empty all the ink in the first 10 pages. That’s why we have to invert the colours in order to consume less ink in printing.

After an hour of searching on the web I came out with empty hands! I have only managed to apply a Gray scale on the PDF using the convert command:

convert uglyPresentation.pdf -colorspace gray prettierPresentation.pdf

I am still having the same problem. The background instead of the ugly bright blue is ugly black/gray.

So I started reading the man page of the convert tool instead of searching on the web. Finally I came up with the -negate argument which replace each pixel with its complementary color.

convert prettierPresentation.pdf -negate beautifulPresentation.pdf

And we are set! Now I can print my presentation consuming less ink!

Conclusion: Read The F*** Manual

It is also well mentioned that you can invert or change the colorspace in other file types, like images.