;;;; -*- 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 M. Rosenberg
;;;;
;;;; cl-photo users are granted the rights to distribute and use this software
;;;; as governed by the terms of the GNU General Public License v2
;;;; (http://www.gnu.org/licenses/gpl.html)
;;;;
;;;; *************************************************************************

(in-package #:photo)

(defun aov-one-dim (focal-length frame-size 
                                 &key (projection :rectilinear)
                                 (magnification 0))
  "Returns the angle of view in one dimension. Default is infinity which
has an magnification of 0."
  (ecase projection
    (:rectilinear
     (radians->degrees (* 2 (atan (/ frame-size 2 focal-length
                                     (1+ magnification))))))
    (: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 aov (focal-length frame-width frame-height
                         &key (projection :rectilinear)
                         (magnification 0))
  "Returns the angle of field of view for a focal length and frame size. 
Default is infinity (magnification 0)"
  (values
   (aov-one-dim focal-length frame-width :projection projection :magnification magnification)
   (aov-one-dim focal-length frame-height :projection projection :magnification magnification)
   (aov-one-dim focal-length (diagonal frame-width frame-height)
                :projection projection :magnification magnification)))

(defun image-distance (focal-length object-distance)
  "Returns the image distance for a focused object at distance using the Gaussian 
Lens Equation."
  (if (= focal-length object-distance)
      0
    (float (/ 1 (- (/ 1 focal-length) (/ 1 object-distance))))))

(defun fov (focal-length frame-width frame-height object-distance
                         &key (projection :rectilinear))
  "Returns the field of view and image magnificaion ratio at a given distance."
  (let* ((image-distance (image-distance focal-length object-distance))
         (magnification (/ image-distance object-distance)))
    (multiple-value-bind (aov-width aov-height aov-diagonal)
        (aov focal-length frame-width frame-height :projection projection
             :magnification magnification)
      (let* ((d-width (* 2 object-distance (tan (degrees->radians (/ aov-width 2)))))
             (d-height (* 2 object-distance (tan (degrees->radians (/ aov-height 2)))))
             (d-diagonal (* 2 object-distance (tan (degrees->radians (/ aov-diagonal 2))))))
        (values d-width d-height d-diagonal magnification)))))

(defun aov-format (focal-length format &key (projection :rectilinear))
  "Returns the angle of field of view for a focal length and frame size at infinity"
  (let ((dim (imager-dimensions format))) 
    (aov focal-length (car dim) (cdr dim) :projection projection)))

(defun magnification (focal-length distance)
  "Returns the image magnification: the ratio of image size to objecct size."
  (float (/ focal-length (- distance focal-length))))

(defun bellows-factor (focal-length distance)
  "Returns the bellows factor, the ratio of effective aperature to actual aperture."
  (1+ (magnification focal-length distance)))