[argyllcms] Re: Fwd: Simple how-to on camera profiling

  • From: "Guy K. Kloss" <g.kloss@xxxxxxxxxxxx>
  • To: "argyllcms@xxxxxxxxxxxxx" <argyllcms@xxxxxxxxxxxxx>
  • Date: Sat, 20 Mar 2010 10:32:36 +1300

On Sat, 20 Mar 2010 06:20:55 Ben Goren wrote:
> On 2010 Mar 19, at 9:45 AM, Karljohan Lundin Palmerius wrote:
> > May I ask how you do to find the coordinates of the fiducial points?
> Actually, I cheat. I open the file in Photoshop and crop it so only the
> target is included. I might rotate it in Photoshop as well.

Well, that  doesn't fully work. As soon as you've got some perspective 
distortions in it that approach will fail. That was also the reason why Graeme 
has introduced the "fourth fiducial point" to be able to overlay a the mesh in 
these perspective cases.

For finding the coordinates ... yes, that's a bit troublesome. In the past 
I've used different approaches. Initially by reading the coordinates after 
opening the image in Gimp (I bet PhotoShop will be just as usable, but for a 
lot higher price). Then I've just mis-used a little Python application (usint 
the ctypes-opencv bindings) that I have once written for another project. With 
it I could easily record rectangular regions of interest (ROIs) for an 
application that I've built for industrial quality control. It would 
additionally spit out the coordinates on the terminal, from where then I have 
copy/pasted them into a shell or Python script for mass application of scanin. 
Unfortunately the camera lacked in resolution, so tolerances of a few pixels 
mattered, and often I had to hand tune the *exact* position of the fiducial 
points after visually inspecting the debug output TIFF that scanin produced.



Guy K. Kloss
Institute of Information and Mathematical Sciences
Te Kura Pūtaiao o Mōhiohio me Pāngarau
Massey University, Albany (North Shore City, Auckland)
473 State Highway 17, Gate 1, Mailroom, Quad B Building
voice: +64 9 414-0800 ext. 9266   fax: +64 9 441-8181
G.Kloss@xxxxxxxxxxxx http://www.massey.ac.nz/~gkloss

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