update README

1 files changed, 47 insertions, 19 deletions

diff --git a/README b/README
index 7a332fc..388f482 100644
--- a/README
+++ b/README
@@ -8,9 +8,6 @@ It uses a database containing names and GPS data. With the given viewpoint
 (the point from which the picture was taken) and two known mountains
 on the picture, gipfel can compute all parameters needed to compute the
 positions of other mountains on the picture.
-Additionally, gipfel can try to guess these parameter if only one mountain
-is known on the picture. In this case, a few other peaks need to be marked,
-but it is not necassary to know their names.
 gipfel can also be used to play around with the parameters manually. But be
 warned: It is pretty difficult to find the right parameters for a given
 picture manually.
@@ -49,23 +46,16 @@ parameters. These are:
 - View direction
 - Nick angle
 - Tilt angle
-- Scale 
+- Focal Length
 - Visibility
 
-Play around with these parameters, until you see the names of one or two 
+Play around with these parameters, until you see the names of 
 mountains, which you already recognize on the picture.
-Now click on the small cross at the left of the name to mark it and drag
-them to the position of the mountain on the picture.
-The marked mountains should have a red flag.
-If you have positioned two mountains, you can now click on the "comp" button
-in the control window. 
-If you have only marked one mountain, you need to mark other peaks on the 
-picture using the green flags which you find at the center of the picture.
-Make sure, that the one marked mountain has a red flag containing a "1" if 
-it has a "2" in its flag, just keep clicking on it until it changes to a "1".
-Then click on the "guess" button. If the result is disapointing, try to adjust
-the visibility parameter as only visible mountains are taken into account
-during the "guess"-process.
+Now middle-click on the small cross at the left of the name to mark it.
+It should turn red. Now you can drag it with the left mouse button pressed
+to the position of the mountain on the picture.
+If you have positioned at least two mountains, you can now click on
+the "comp" button in the control window. 
 
 You may also want to have a look at the screen video at
 http://www.ecademix.com/JohannesHofmann/gipfel.avi
@@ -153,6 +143,8 @@ Use the multiple TIFF option for blending the result with enblend
 (http://enblend.sourceforge.net/).
 The width and height of the result images can be adjusted with the
 -w and -h options.
+You can use the -b switch to enable bilinear interpolation, which 
+gives better results but is a bit slower.
 
 The nice thing about stitching is that gipfel uses the same code that
 it already had for positioning mountains on the pictures.
@@ -167,6 +159,40 @@ If you want to open a stitched image in gipfel to locate the mountains
 on it, don't forget to choose Panoramic Projection!
 
 
+Exif Data
+=========
+
+gipfel tries to get useful information from the exif data of the
+input image. It uses the "Focal Length in 35mm Film" and the 
+"GPS Longitude", "GPS Latitude", and "GPS Height" parameters, if they
+exist.
+
+
+Lens Distortion
+===============
+
+Typical lenses especially wide-angle lenses diverge from the optimal
+rectilinear projection.
+gipfel can now partly correct the resulting errors.
+To this end gipfel uses a standard distortion model with two parameters 
+(k0 and k1). Depending on these values, the distance d of an image point
+from the center is modified by (k0 * d + k1 * d ^ 2).
+
+If you mark and position more than 3 mountains on an image, gipfel
+tries to correct lens distortion. You can see that the flags turn
+green in this case.
+Once you have reasonable values for k0 and k1 for a special camera and
+focal length you can save the distortion profile (Distortion/Save Profile).
+Whenever you now open an image taken with this camera model and focal
+length, gipfel will use this distortion profile.
+The distortion profiles are stored in the 
+$HOME/.fltk/Johannes.HofmannATgmx.de/gipfel directory and can also be
+edited manually.
+Independent of the distortion profiles one can also modify the
+distortion parameters per image.
+Distortion correction is also used when stitching panorama images.
+
+
 Troubleshooting
 ===============
 
@@ -177,8 +203,8 @@ you can build up your own datafile.
 
 - gipfel only works with full normal unmodified pictures taken with a 
 non-distorting standard objektive. If you have a panorama picture, you
-might want to try the experimental "Panoramic Projection" support (see
-"Options" menu).
+might want to try the "Panoramic Projection" support which 
+imlements a cylindrical projection (see "Projection" menu).
 
 - I have no idea, whether gipfel works correctly on pictures taken on
 the southern hemisphere, but I would appreciate any feedback about it.
@@ -202,6 +228,8 @@ Also have look at their other site http://www.alpen-panoramen.de/ !
 Thanks to George J. Gesslein II for his great program mathomatic
 (http://www.mathomatic.com/) which helped a lot to handle and simplify large
 Expressions.
+In newer versions I use maxima (http://maxima.sourceforge.net/) for
+symbolic computation and code generation.
 I also want to thank my brother Martin Hofmann for his suggestions and the
 discussions.