;;;; -*- Mode: LISP; Syntax: ANSI-Common-Lisp; Base: 10; Package: photo -*-
;;;; *************************************************************************
;;;; FILE IDENTIFICATION
;;;;
;;;; Name:          fov.lisp
;;;; Purpose:       Field of view functions for cl-photo
;;;; Programmer:    Kevin M. Rosenberg
;;;; Date Started:  April 2005
;;;;
;;;; $Id$
;;;;
;;;; This file, part of cl-photo, is Copyright (c) 2005 by Kevin Rosenberg.
;;;; Rights of modification and redistribution are in the LICENSE file.
;;;;
;;;; *************************************************************************

(in-package #:photo)

(defun fov-one-dim (focal-length frame-size 
                                 &key (projection :rectilinear))
  (ecase projection
    (:rectilinear
     (radians->degrees (* 2 (atan (/ frame-size 2 focal-length)))))
    (:equisolid 
     (radians->degrees (* 4 (asin (/ frame-size 4 focal-length)))))
    (:equidistance 
     (radians->degrees (/ (* 2 frame-size) focal-length)))
    (:orthogonal
     (radians->degrees (* 2 (asin (/ frame-size 2 focal-length)))))
    (:stereographic
     (radians->degrees (* 4 (atan (/ frame-size 4 focal-length)))))
    ))
    
  
(defun fov (focal-length frame-width frame-height
                         &key (projection :rectilinear))
  "Returns the angle of field of view for a focal length and frame size at infinity"
  (values
   (fov-one-dim focal-length frame-width :projection projection)
   (fov-one-dim focal-length frame-height :projection projection)
   (fov-one-dim focal-length (diagonal frame-width frame-height)
                :projection projection)))

(defun fov-format (focal-length format &key (projection :rectilinear))
  "Returns the angle of field of view for a focal length and frame size at infinity"
  (ecase format
    (:aps-c
     (fov focal-length 22.7 15.1 :projection projection))
    (:aps
     (fov focal-length 24 18 :projection projection))
    (:35mm
     (fov focal-length 36 24 :projection projection))
    (:4.5x6
     (fov focal-length 45 60 :projection projection))
    (:6x6
     (fov focal-length 60 60 :projection projection))
    (:6x7
     (fov focal-length 60 70 :projection projection))
    (:6x9
     (fov focal-length 60 90 :projection projection))
    (:4x5
     (fov focal-length (* 4 +inches->mm+) (* 5 +inches->mm+)
          :projection projection))
    (:8x10
     (fov focal-length (* 8 +inches->mm+) (* 10 +inches->mm+)
          :projection projection))
    ))