Print image to cups-pdf without rescaling

Question

If I print a png file to a cups-pdf printer, using lp, the pic is adjusted to the page size (i'm assuming), even though fitplot is false.

lp ~/Pictures/tux-db.png

Here is output of lpoptions:

copies=1 device-uri=cups-pdf:/ finishings=3 fitplot=false job-hold-until=no-hold job-priority=50 job-sheets=none,none marker-change-time=0 mirror=false number-up=1 orientation-requested=3 ppd-timestamp=* printer-commands=AutoConfigure,Clean,PrintSelfTestPage printer-info=PDF printer-is-accepting-jobs=true printer-is-colormanaged=true printer-make-and-model='Generic CUPS-PDF Printer' printer-state=3 printer-state-change-time=1464004024 printer-state-reasons=none printer-type=8450124 printer-uri-supported=ipp://localhost:631/printers/PDF scaling=100

The generated pdf is here.

If I open the png file with Image Viewer, and print it, I get a correct size pdf (small picture), so the printer is capable of printing the correct size. Pdf file here.

What is the right option to use?

Using ubuntu 14.04.

Just to clear, the final goal is to use cups API in my own sw, with the correct option, so I can print images without rescaling (to avoid resizing small images to large sizes).

Answer 1

It turns out that the answer is the scaling parameter. I thought the parameter was relative to the image, but turns out it is relative to the page.

So setting scaling=0 will print the image on its native size. It is possible to also manipulate it using the ppi (pixel per inch), and the natural-scaling parameter. More info here.