We've got a HP Color LaserJet 2605dn printer, and are using the official hplip drivers on our Linux machines.
Unfortunately, full-size images always got printed too dark.
After playing around with imagemagick's convert to increase brightness of the images before printing, I finally found a way to adjust the brightness via the gamma value inside the CUPS printer settings:
- Open the printer management window. Right-click the printer, click "Properties".
- Select "Job options" and expand "More" below "Image options". Adjust the gamma value. For us, 1250 gave us much nicer results compared to the standard setting of 1000.
