There is a problem with the HPLIP printing system (drivers or filters), causing printed colours to be wrong. Apologies for double-posting this, but it does not belong in the hardware section any longer (http://www.pclinuxos.com/forum/index.php/topic,87414.0.html
I've done some testing and summarise the results below in the hope that it may help investigation into this bug.
My printer is an HP C6380 All-In-One
I removed/deleted it completely, rebooted and started again:
Re-installed the printer using the CUPS web interface, choosing the driver hpcups 18.104.22.168. No foomatic driver option given, even though foomatic is installed on my system (other printers had both hpcups and foomatic driver choices available)
Printed the CUPS test page. The black/white gradient was broken, having a red line in the middle (link to scanned copy
Ran PrinterDrake (PCC > Hardware > Set up the printer(s)...)
Printed the PrinterDrake Standard and Photo test pages. On the standard page the colour wheel again had broken black/white gradients, but the colour gradients were fine (link to scanned copy
Strangely, the photo test page appeared to be completely OK (link to scanned copy
However, my initial problem of photos printed from Picasa remains; all the pictures look slightly like negatives which, by the look of it, seems to be related to the broken black/white gradient problem (link to scanned copy
). Just for info, the turquoise colour of the outfits is correct, it's the black highlights/lowlights/backgrounds that are screwed up.
Exactly the same problems/symptoms appear if I install the printer using PrinterDrake or hp-setup/HP Device Manager.
More proof (if any were needed) that the problem is black/grayscale-related:
On the colour charts linked below, where the colour wheel fades to white in the middle, there is very little problem, but where it fades to black, it seems to cross a boundary at about 70% black where it is printed as bright red and then the gradient starts at white again.
The more black in the picture, the greater the problem.
(Source colour wheel - sorry for the poor quality screenshot
) and (Printed colour wheel
Looking at some other stuff online, I'm guessing the problem may be to do with filters (/usr/lib/cups/filter/hpcups ??) rather than the driver itself?
I really hope someone is able to investigate this bug, as it is a real shame that I cannot print photos at the moment.