== name ==

EXIF info

== category ==

Digital Photography

== author ==

Kevin Layer (mailto(layer@franz.com)), based on Matthias Wandel's
href(jhead,http://www.sentex.net/~mwandel/jhead).  Based on, in the
sense that reading italic(jhead) was easier than reading the
href(EXIF specs,http://www.exif.org/specifications.html).

== author-image ==

== short-description ==

A Lisp program to read href(EXIF,http://www.exif.org) (Exchangeable
Image File Format) 2.2 information from files produced by digital
still cameras.

== long-description ==

When a digital camera stores a photographic image onto removable media
it stores along with the image data some meta data such as exposure,
ISO rating, whether or not the flash was used, the image width and
length, and the date on which the image was created.  It is useful to
be able to read this meta data.  For example, it allows the easy
creation of a program to rename digital camera files to file names
containing the date the photo was originally taken.

The files produced by digital cameras are usually EXIF format files.

The utility presented here allows a Common Lisp program to extract the
meta data about a photograph from an EXIF format file.

== examples ==

The function italic(parse-exif-data) returns a structure containing
all the meta information about the image file:

  cl-user(10): (describe
		(parse-exif-data
                 "c:/pictures/_TMP/20041128-1515-1200-S1IS.JPG"))
  #<exif-info @ #x2072d512> is a structure of type exif-info.
  It has these slots:
   file               "c:/pictures/_TMP/20041128-1515-1200-S1IS.JPG"
   make               "Canon"
   model              "Canon PowerShot S1 IS"
   date               "2004:11:28 15:15:12"
   comment            ""
   exposure           0.00125
   f-number           4.5
   iso-rating         nil
   exposure-bias-value  0.0
   subject-distance   nil
   flash              t
   focal-length       48.578
   image-width        2048
   image-length       1536
  cl-user(11): 

== instructions ==

All the below symbols are defined in the italic(util.exif) package.

italic(parse-exif-data) takes a single argument, a file name, and
returns a structure, the slots of which can be accessed with the
following accessors:

* make-exif-info
* exif-info-file
* exif-info-make
* exif-info-model
* exif-info-date
* exif-info-comment
* exif-info-exposure
* exif-info-f-number
* exif-info-iso-rating
* exif-info-exposure-bias-value
* exif-info-subject-distance
* exif-info-flash
* exif-info-focal-length
* exif-info-image-width
* exif-info-image-length

== tutorial ==

Getting started:

  cl-user(12): :cf exifinfo
  ;;; Compiling file exifinfo.cl
  ;;; Writing fasl file exifinfo.fasl
  ;;; Fasl write complete
  cl-user(14): :ld exifinfo
  ; Fast loading c:\src\exif-utils\exifinfo.fasl
  cl-user(15): (use-package :util.exif)
  t
  cl-user(16): 

Now, you're ready to do some real work:

  cl-user(16): (setq exif
		 (parse-exif-data
		  "c:/pictures/_TMP/20041128-1515-1200-S1IS.JPG"))
  #S(exif-info :file "c:/pictures/_TMP/20041128-1515-1200-S1IS.JPG"
	       :make "Canon"
	       :model "Canon PowerShot S1 IS"
	       :date "2004:11:28 15:15:12"
	       :comment ...)
  cl-user(17): (exif-info-make exif)
  "Canon"
  cl-user(18): (exif-info-model exif)
  "Canon PowerShot S1 IS"
  cl-user(19): (exif-info-date exif)
  "2004:11:28 15:15:12"
  cl-user(20): 

== home-url ==

== doc-url ==

http://www.exif.org

== license ==

The code referenced here is in the public domain.

== book ==

== references ==

href(http://www.exif.org,http://www.exif.org) contains information
about the EXIF file format.

href(ISO/IEC 10918-1:1994,http://www.iso.ch/iso/en/CatalogueDetailPage.CatalogueDetail?CSNUMBER=18902&ICS1=35)
document.

href(jhead,http://www.sentex.net/~mwandel/jhead), which the author of
this utility used to understand EXIF.

== source-fooball ==

href(exifinfo.cl,/source/exifinfo.cl)

== release-date ==

1/5/2005

== release-version ==

1.6

== status ==

Stable.

I have tried reading the files from a variety of cameras, but that's
no guarantee that it will work on all EXIF files.

== history ==

* December 31, 2000: initial version

* December 26, 2002: fix problem dealing with Photoshop 7 written
images.

* May 17, 2004: fix traveral of directories, being able to read Thumbs
Plus manipulated files.

== acl-dependencies ==

None.

== other-dependencies ==

None.

== platform ==

Should work on ACL version 6.0 or later.

== ad ==