From 8910ad89a31d63e822079b060e4e2903c455fa75 Mon Sep 17 00:00:00 2001
From: "Kevin M. Rosenberg" <kevin@rosenberg.net>
Date: Tue, 10 May 2005 20:26:00 +0000
Subject: [PATCH] r10526: improve print-magnification with crop function

---
 dof.lisp     | 21 +++++++++++++++------
 fov.lisp     | 11 +++++++++++
 package.lisp |  1 +
 3 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/dof.lisp b/dof.lisp
index 11f158c..8dfdf14 100644
--- a/dof.lisp
+++ b/dof.lisp
@@ -19,17 +19,26 @@
 
 (in-package #:photo)
 
+(defun sort-size (size)
+  "Returns a cons pair with the smaller size first."
+  (if (>= (car size) (cdr size))
+      (cons (cdr size) (car size))
+      (cons (car size) (cdr size))))
+  
+(defun print-magnification (imager-size print-size)
+  "Returns the magnification required between an imager and print sizes
+while taking crop into consideration."
+  (setf imager-size (sort-size imager-size))
+  (setf print-size (sort-size print-size))
+  (float (max (/ (car print-size) (car imager-size))
+	      (/ (cdr print-size) (cdr print-size)))))
+
 (defun coc (imager-size &key (lpm 5) (minimum-distance 250) 
                    (viewing-distance 250)
                    (print-size (output-dimensions :8x10in)))
   "Returns circle of confusion in mm and print magnification for a format. 
 Default resolving power is 5 lpm at 25cm."
-
-  (let* ((imager-max (max (car imager-size) (cdr imager-size)))
-	 (imager-min (min (car imager-size) (cdr imager-size)))
-	 (print-max (max (car print-size) (cdr print-size)))
-	 (print-min (min (car print-size) (cdr print-size)))
-	 (magnification (max (/ print-max imager-max) (/ print-min imager-min)))
+  (let* ((magnification (print-magnification imager-size print-size))
 	 (resolution-factor (/ (* magnification lpm minimum-distance) viewing-distance))
 	 (coc (/ 1.0d0 resolution-factor)))
     (values coc magnification)))
diff --git a/fov.lisp b/fov.lisp
index 211820a..6fec649 100644
--- a/fov.lisp
+++ b/fov.lisp
@@ -208,3 +208,14 @@ Returns: focal-length object-distance image-distance magnification bellows-facto
   "Returns the bellows factor, the ratio of effective aperature to actual aperture."
   (1+ (magnification :focal-length focal-length :object-distance object-distance)))
 
+(defun extension-tube (focal-length &key original-object-distance new-object-distance original-image-distance
+					 new-object-distnace original-magnification new-magification
+					 extension-length (units :feet))
+  "Computes the parameters for using extension tubes.
+Requires: 1. original-object-distance, original-image-distance, or original-magnification
+          2. new-object-distance, new-image-distance, new-magnification, or extension-length
+Returns: original-object-distance, original-image-distance, original-magnification,
+         new-object-distance, new-image-distance, new-magnification, extension-length."
+  )
+
+
diff --git a/package.lisp b/package.lisp
index 5b28e2d..ffdf7e7 100644
--- a/package.lisp
+++ b/package.lisp
@@ -42,6 +42,7 @@
    #:close-up
    
    ;; dof.lisp
+   #:print-magnification
    #:coc
    #:coc-format
    #:coc-pixels
-- 
2.34.1