Help with Lensfun (as a dev)

CarVac · August 18, 2019, 10:03pm

How do you, uh, actually use lensfun?

I’m having a hard time figuring out what information I need to give, what functionality it provides and what I need to code up myself…

ggbutcher · August 18, 2019, 11:57pm

Here’s my routine in rawproc:

github.com

butcherg/rawproc/blob/master/src/PicProcessorLensCorrection.cpp#L450

    
      
          			const lfCamera ** cameras = ldb->FindCamerasExt(NULL, camspec.c_str());
          			if (cameras) {
          				cam = cameras[0];
          				success = true;
          			}
          			else {
          				wxMessageBox(wxString::Format(_("Error: Cannot find a camera matching %s in database."), camspec.c_str()));
          				success = false;
          			}
          			lf_free (cameras);
          
          
			const lfLens *lens = NULL;
          			const lfLens **lenses = NULL;
          			if (success) {
          				// try to find a matching lens in the database
          				lenses = ldb->FindLenses (cam, NULL, lensspec.c_str());
          				if (lenses) {
          					lens = lenses [0];
          					success = true;
          				}
          				else {

The actual lensfun “fun” starts at 530, and is to the old API, 0.3.2 IIRC. You can do each modification separately, or the lfModifier allows one to combine chromatic abberation and distortion in one pass.

I had to code up GetR(float x, float y), GetG(float x, float y), and GetB(float x, float y) methods for my image library; there is an expectation of an interpolation to get the correct pixel, and I just got the nearest neighbor to start. I’ll do a better interpolation in rawproc2…

Thanatomanic · August 19, 2019, 5:39am

Have you seen the docs? I always thought they contain everything you need afaik, including sample code
https://lensfun.github.io/manual/v0.3.2/