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;;; el-exiftool.el --- Elisp wrapper around ExifTool -*- lexical-binding: t -*-
;; Elisp wrapper around ExifTool
;; Copyright (C) 2017 by Arun I
;;
;; Author: Arun I <arunisaac@systemreboot.net>
;; Version: 0.1
;; Keywords: data
;; Homepage: https://git.systemreboot.net/el-exiftool
;; Package-Requires: ((emacs "25"))
;; This file is part of el-exiftool.
;; el-exiftool is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;; el-exiftool is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with el-exiftool. If not, see <http://www.gnu.org/licenses/>.
;;; Commentary:
;;
;; el-exiftool is an elisp wrapper around ExifTool. ExifTool supports
;; reading and writing metadata in various formats including EXIF, XMP
;; and IPTC.
;;
;; There is a significant overhead in loading ExifTool for every
;; command to be exected. So, el-exiftool starts an ExifTool process
;; in the -stay_open mode, and passes all commands to it. For more
;; about ExifTool's -stay_open mode, see
;; http://www.sno.phy.queensu.ca/~phil/exiftool/#performance
;;; Code:
(require 'cl-macs)
(require 'subr-x)
(require 'tq)
(defun el-exiftool--tq-sync-query (tq question regexp)
"Add a transaction to transaction queue TQ, block and read response.
See `tq-enqueue' for details of arguments QUESTION and REGEXP."
(let ((response))
(tq-enqueue tq question regexp nil
(lambda (_ answer) (setq response answer)))
(while (not response)
(accept-process-output))
response))
(defun el-exiftool-run ()
"Start an exiftool process if one is not already running.
If an exiftool process is already running, delete it, and create
a new one. Return the process object of the newly created
process."
(when-let (exiftool (get-process "exiftool"))
(delete-process exiftool))
(start-process "exiftool" "exiftool" "exiftool" "-stay_open" "True" "-@" "-"))
(let ((tq (tq-create (el-exiftool-run))))
(defun el-exiftool-command (&rest args)
"Execute a command in the currently running exiftool process.
ARGS are arguments of the command to be run, as provided to the
exiftool command line application."
(string-trim
(let ((suffix "{ready}\n"))
(string-remove-suffix
suffix (el-exiftool--tq-sync-query
tq (concat (string-join args "\n")
"\n-execute\n")
suffix))))))
(defun el-exiftool-read (file &rest tags)
"Read TAGS from FILE, return an alist mapping TAGS to values.
If a tag is not found, return an empty string \"\" as the
value. If no TAGS are specified, read all tags from FILE.
\(fn FILE TAG...)"
(mapcar
(lambda (line)
(cl-destructuring-bind
(tag value) (split-string line ": ")
(let ((value (if (equal value "-") "" value)))
(cons tag value))))
(split-string
(apply 'el-exiftool-command
"-s" "-s" "-f"
(append
(mapcar (apply-partially 'format "-%s") tags)
(list file)))
"\n+")))
(defun el-exiftool-copy (source destination &rest tags)
"Copy TAGS from SOURCE file to DESTINATION file.
If no TAGS are specified, copy all tags from SOURCE."
(apply 'el-exiftool-command
"-overwrite_original"
"-tagsFromFile" source
(append
(mapcar (apply-partially 'format "-%s") tags)
(list "-all:all" destination)))
(message "Tags from %s copied to %s" source destination)
destination)
(defun el-exiftool-write (file &rest tag-value-alist)
"Write tags to FILE.
The metadata to be written is specified as (TAG . VALUE)
pairs. Specifying the empty string \"\" for VALUE deletes that
TAG.
\(fn FILE (TAG . VALUE)...)"
(apply 'el-exiftool-command
"-m" "-overwrite_original"
(append
(mapcar
(cl-function
(lambda ((tag . value))
(format "-%s=%s" tag value)))
tag-value-alist)
(list file))))
(provide 'el-exiftool)
;;; el-exiftool.el ends here
|
