r10526: improve print-magnification with crop function

[cl-photo.git] / dof.lisp

diff --git a/dof.lisp b/dof.lisp
index 11f158c77457b591d43f94e75abd89e6a70eb4f7..8dfdf1478ac32981d9472a92fc1bb7d1d6e70e33 100644 (file)
--- 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)))