(let* (;; FILEからExifを読み込む。
       (exif (or (my-exif-parse-file file)
                 (error "No Exif Data")))
       ;; 撮影日時を取得する。
       (time (or (my-exif-date-time-original exif)
                 (error "No Exif.DateTimeOriginal")))
       ;; 撮影位置を取得する。
       (latlng (or (my-exif-latlng exif) ;;From GPS Info
                   (my-location-latlng-at-time time)))) ;From GPX File
  latlng)

(require 'exif)
(exif-parse-file "~/tmp/20190826_163620.jpg"))

;; exif.elより
(defvar exif-tag-alist
  '((11 processing-software)
    (271 make)
    (272 model)
    (274 orientation)
    (282 x-resolution)
    (283 y-resolution)
    (296 resolution-unit)
    (305 software)
    (306 date-time)
    (315 artist))
  "Alist of tag values and their names.")

(defun my-exif-prop-find (exif tag)
  (seq-find (lambda (e) (equal (plist-get e :tag) tag)) exif))
(defun my-exif-parse-file (file)
  (cl-letf* (((symbol-function 'exif--parse-directory-old)
              (symbol-function 'exif--parse-directory))
             ((symbol-function 'exif--parse-directory)
              (lambda (le)
                (let ((exif (exif--parse-directory-old le)) ;;元の関数を呼び出す
                      (pointer-tags '(34665 34853))) ;;Exif IFD Pointer, GPS Info IFD Pointer
                  (dolist (tag pointer-tags)
                    (let* ((property (my-exif-prop-find exif tag))
                           (offset (plist-get property :value)))
                      (when (integerp offset)
                        (goto-char (1+ offset))
                        ;; :valueのオフセットから情報を読み取り、:pointeeとして追加する
                        (nconc property (list :pointee
                                              (exif--parse-directory le))))))
                  exif))))
    (exif-parse-file file)))

(my-exif-parse-file "~/tmp/20190826_163620.jpg")

(defun my-exif-prop-value (exif tag &optional key)
  (plist-get (my-exif-prop-find exif tag) (or key :value)))

(let* ((exif (my-exif-parse-file "~/tmp/20190826_163620.jpg"))
       (exif-ifd (my-exif-prop-value exif 34665 :pointee))
       (date-time-original (my-exif-prop-value exif-ifd 36867)))
  date-time-original)

(let* ((exif (my-exif-parse-file "~/tmp/20190826_163620.jpg"))
       (gps-ifd (my-exif-prop-value exif 34853 :pointee)))
  (list
    (my-exif-prop-value gps-ifd 1)
    (my-exif-prop-value gps-ifd 2)
    (my-exif-prop-value gps-ifd 3)
    (my-exif-prop-value gps-ifd 4)))

(defun exif--process-value (value type le)
  "Do type-based post-processing of the value."
  (cl-case type
    ;; Chop off trailing zero byte.
    ('ascii (substring value 0 (1- (length value))))
    ('rational (with-temp-buffer
                 (set-buffer-multibyte nil)
                 (insert value)
                 (goto-char (point-min))
                 ;; ここから
                 (let* ((num-values (/ (length value) 8))
                        (nums (cl-loop repeat num-values
                                       collect (cons (exif--read-number 4 le)
                                                     (exif--read-number 4 le)))))
                   (if (= num-values 1)
                       (car nums)
                     nums))
                 ;; ここまで修正
                 ))
    (otherwise value)))

(let* ((exif (my-exif-parse-file "~/tmp/20190826_163620.jpg"))
       (gps-ifd (my-exif-prop-value exif 34853 :pointee)))
  (list
    (my-exif-prop-value gps-ifd 1)
    (my-exif-prop-value gps-ifd 2)
    (my-exif-prop-value gps-ifd 3)
    (my-exif-prop-value gps-ifd 4)))

(defun my-exif-3rationals-to-float (v neg)
  (let ((value (+
                (/ (caar v) (* 1.0 (cdar v)))
                (/ (caadr v) (* 60.0 (cdadr v)))
                (/ (caaddr v) (* 3600.0 (cdaddr v))))))
    (if neg (- value) value)))

(let* ((exif (my-exif-parse-file "~/tmp/20190826_163620.jpg"))
       (gps (my-exif-prop-value exif 34853 :pointee)))
  (format "%.6f,%.6f"
          (my-exif-3rationals-to-float (my-exif-prop-value gps 2)
                                       (string= (my-exif-prop-value gps 1) "S"))
          (my-exif-3rationals-to-float (my-exif-prop-value gps 4)
                                       (string= (my-exif-prop-value gps 1) "W"))))

(require 'exif)

(defun my-exif-prop-find (exif tag)
  (seq-find (lambda (e) (equal (plist-get e :tag) tag)) exif))

(defun my-exif-prop-value (exif tag &optional key)
  (plist-get (my-exif-prop-find exif tag) (or key :value)))

(defun my-exif-3rationals-to-float (v neg)
  (let ((value (+
                (/ (caar v) (* 1.0 (cdar v)))
                (/ (caadr v) (* 60.0 (cdadr v)))
                (/ (caaddr v) (* 3600.0 (cdaddr v))))))
    (if neg (- value) value)))

;;

(defun my-exif-parse-file (file)
  (cl-letf (((symbol-function 'exif--parse-jpeg)
             #'my-exif--find-app1-exif-in-jpeg) ;; [BugFix] Support APP1 segments that are not Exif (Such as XMP)
            ((symbol-function 'exif--parse-exif-chunk)
             #'my-exif--parse-exif-chunk))
    (exif-parse-file file)))

(defun my-exif--find-app1-exif-in-jpeg ()
  (unless (= (exif--read-number-be 2) #xffd8) ; SOI (start of image)
    (signal 'exif-error "Not a valid JPEG file"))
  (cl-loop for segment = (exif--read-number-be 2)
           for size = (exif--read-number-be 2)
           ;; Stop parsing when we get to SOS (start of stream);
           ;; this is when the image itself starts, and there will
           ;; be no more chunks of interest after that.
           while (not (= segment #xffda)) ;;FFDA=SOS
           do (if (and (= segment #xffe1) ;;FFE1=APP1
                       (equal (save-excursion (exif--read-chunk 6))
                              (string ?E ?x ?i ?f ?\0 ?\0)))
                  ;; Return APP1 Exif
                  ;; (Matched to return value of exif--parse-jpeg)
                  (cl-return (list
                              (cons segment (exif--read-chunk (- size 2)))))
                ;; Skip segment
                (forward-char (- size 2)))))

(defun my-exif--parse-exif-chunk (data)
  (with-temp-buffer
    (set-buffer-multibyte nil)
    (insert data)
    (goto-char (point-min))
    ;; The Exif data is in the APP1 JPEG chunk and starts with
    ;; "Exif\0\0".
    (unless (equal (exif--read-chunk 6) (string ?E ?x ?i ?f ?\0 ?\0))
      (signal 'exif-error "Not a valid Exif chunk"))
    (delete-region (point-min) (point))
    (let* ((endian-marker (exif--read-chunk 2))
           (le (cond
                ;; "Motorola" is big-endian.
                ((equal endian-marker "MM")
                 nil)
                ;; "Intel" is little-endian.
                ((equal endian-marker "II")
                 t)
                (t
                 (signal 'exif-error
                         (format "Invalid endian-ness %s" endian-marker))))))
      ;; Another magical number.
      (unless (= (exif--read-number 2 le) #x002a)
        (signal 'exif-error "Invalid TIFF header length"))
      (let ((offset (exif--read-number 4 le))) ;; <==== [BugFix] 2 => 4 ====
        ;; Jump to where the IFD (directory) starts and parse it.
        (when (> (1+ offset) (point-max))
          (signal 'exif-error "Invalid IFD (directory) offset"))
        (goto-char (1+ offset))
        (my-exif--parse-directory le)))))

(defun my-exif--parse-directory (le)
  (let ((dir
         (cl-loop repeat (exif--read-number 2 le)
                  collect (my-exif--read-value le))))
    (let ((next (exif--read-number 4 le)))
      (if (> next 0)
          ;; There's more than one directory; if so, jump to it and
          ;; keep parsing.
          (progn
            (when (> (1+ next) (point-max))
              (signal 'exif-error "Invalid IFD (directory) next-offset"))
            (goto-char (1+ next))
            (nconc dir (my-exif--parse-directory le)))
        ;; We've reached the end of the directories.
        dir))))

(defvar my-exif-pointer-tags '(34665 ;;Exif IFD Pointer
                               34853)) ;;GPS Info IFD Pointer

(defun my-exif--read-value (le)
  ;; [Add] Support multiple components
  ;; [BugFix] Reading small value length < 4 and big-endian
  (let* ((tag (exif--read-number 2 le))
         (format (exif--read-number 2 le))
         (field-format (my-exif--field-format format))
         (type (car field-format))
         (bytes/component (cdr field-format))
         (num-components (exif--read-number 4 le))
         (num-bytes (* num-components bytes/component))
         (components
          (save-excursion
            (when (> num-bytes 4)
              ;; If the length of the data is
              ;; more than 4 bytes, then it's
              ;; actually stored after this
              ;; directory, and the value
              ;; here is just the offset to
              ;; use to find the data.
              (let ((offset (exif--read-number 4 le)))
                (when (> (+ (1+ offset) num-bytes)
                         (point-max))
                  (signal 'exif-error
                          "Premature end of file"))
                (goto-char (1+ offset))))

            (pcase type
              ;;@todo support signed
              ;;@todo support float and double
              ((or 'byte 'short 'long
                   's-byte 's-short 's-long)
               (cl-loop repeat num-components
                        collect (exif--read-number bytes/component le)))
              ((or 'rational 's-rational)
               (cl-loop repeat num-components
                        collect (cons
                                 (exif--read-number 4 le)
                                 (exif--read-number 4 le))))
              ('ascii
               (buffer-substring (point) (+ (point) num-bytes -1)));;Chop off trailing zero byte.
              ('undefined
               (buffer-substring (point) (+ (point) num-bytes)))
              (_
               nil))))
         (value (cond
                 ((eq type 'ascii)
                  components)
                 ((eq type 'undefined)
                  components)
                 ((= num-components 1)
                  (car components))
                 (t
                  components)))
         (pointee (when (and (memq tag my-exif-pointer-tags)
                             (integerp value))
                    (save-excursion
                      (goto-char (1+ value))
                      (my-exif--parse-directory le)))))
    ;; Skip Value (4 bytes)
    (goto-char (+ (point) 4))

    (nconc
     (list
      :tag tag
      :tag-name (cadr (assq tag my-exif-tag-alist))
      :format format
      :format-type (car field-format)
      :value value)
     (when pointee
       (list :pointee pointee)))))

(defun my-exif--field-format (number)
  (cl-case number
    (1 (cons 'byte 1))
    (2 (cons 'ascii 1))
    (3 (cons 'short 2))
    (4 (cons 'long 4))
    (5 (cons 'rational 8))
    (6 (cons 's-byte 1))
    (7 (cons 'undefined 1))
    (8 (cons 's-short 2))
    (9 (cons 's-long 4))
    (10 (cons 's-rational 8))
    (11 (cons 'float 4))
    (12 (cons 'double 8))
    (otherwise (cons 'unknown 1))))

(defvar my-exif-tag-alist
  '((11 processing-software)
    (256 image-width)
    (257 image-length)
    (258 bits-per-sample)
    (259 compression)
    (262 photometric-interpretation)
    (270 image-description)
    (271 make)
    (272 model)
    (273 strip-offsets)
    (274 orientation)
    (277 samples-per-pixel)
    (282 x-resolution)
    (283 y-resolution)
    (296 resolution-unit)
    (305 software)
    (306 date-time)
    (315 artist)
    (513 jpeg-interchange-format)
    (514 jpeg-interchange-format-length)
    (531 ycbcr-positioning)
    (33434 exposure-time)
    (33437 f-number)
    (34665 exif-ifd-pointer)
    (34850 exposure-program)
    (34853 gps-info-ifd-pointer)
    (34855 iso-speed-ratings)
    (36864 exif-version)
    (36867 date-time-original)
    (36868 date-time-digitized)
    (37121 components-configuration)
    (37377 shutter-speed-value)
    (37378 aperture-value)
    (37379 brightness-value)
    (37380 exposure-bias-value)
    (37381 max-aperture-value)
    (37382 subject-distance)
    (37383 metering-mode)
    (37384 light-source)
    (37385 flash)
    (37386 focal-length)
    (37520 sub-sec-time)
    (37521 sub-sec-time-original)
    (37522 sub-sec-time-digitized)
    (40960 flashpix-version)
    (40961 color-space)
    (40962 pixel-x-dimension)
    (40963 pixel-y-dimension)
    (40964 related-sound-file)
    (40965 interoperability-tag)
    (41495 sensing-method)
    (41729 scene-type)
    (41985 custom-rendered)
    (41986 exposure-mode)
    (41987 white-balance)
    (41988 digital-zoom-ratio)
    (41989 focal-length-in-35mm-film)
    (41990 scene-capture-type)
    (41991 gain-control)
    (41992 contrast)
    (41993 saturation)
    (41994 sharpness)
    (41995 device-setting-description)
    (41996 subject-distance-range))
  "Alist of tag values and their names.")

;;

(defun my-exif-encode-date-time (exif-date-time-str)
  (when exif-date-time-str
    (encode-time
     (nconc
      (nreverse
       (mapcar #'string-to-number
               (split-string exif-date-time-str "[ :]")))
      (list nil nil nil)))))

(defun my-exif-date-time-original (exif)
  (when-let ((exif-ifd (my-exif-prop-value exif 34665 :pointee))
             (date-time-original (my-exif-prop-value exif-ifd 36867)))
    (my-exif-encode-date-time date-time-original)))

(defun my-exif-latlng (exif)
  (when-let ((gps (my-exif-prop-value exif 34853 :pointee))
             (lat-ref (my-exif-prop-value gps 1))
             (lat (my-exif-prop-value gps 2))
             (lng-ref (my-exif-prop-value gps 3))
             (lng (my-exif-prop-value gps 4)))
    (cons
     (my-exif-3rationals-to-float lat
                                  (string= lat-ref "S"))
     (my-exif-3rationals-to-float lng
                                  (string= lng-ref "W")))))

(let ((exif (my-exif-parse-file "~/tmp/20190826_163620.jpg")))
  (list
   (format-time-string "%Y-%m-%d %H:%M:%S" (my-exif-date-time-original exif))
   (my-exif-latlng exif)))

(require 'widget)

;; ダブルクリック、トリプルクリックに対応した `widget-button-click' の代わりです。
(defun my-widget-button-click (event)
  (interactive "e")
  ;; Add double and triple click support to widget-button-release-event-p
  (cl-letf (((symbol-function 'widget-button-release-event-p)
             'my-widget-button-release-event-p))
    (widget-button-click event)))

;; ダブルクリック、トリプルクリックに対応した `my-widget-button-release-event-p' の代わりです。
(defun my-widget-button-release-event-p (event)
  (and (eventp event)
       (memq (event-basic-type event) '(mouse-1 mouse-2 mouse-3))
       (or (and (or (memq 'double (event-modifiers event)) ;;double click
                    (memq 'triple (event-modifiers event))) ;;triple click
                (null (memq 'down (event-modifiers event))))
           (memq 'click (event-modifiers event))
           (memq 'drag (event-modifiers event)))))

(defvar my-push-button-map
  (let ((km (make-sparse-keymap)))
    (define-key km [drag-mouse-1] 'ignore)
    (define-key km [double-down-mouse-1] 'my-widget-button-click)
    (define-key km [triple-down-mouse-1] 'my-widget-button-click)
    km))


(defvar-local my-number-widget nil)
(defun my-increase (delta)
  (widget-value-set
   my-number-widget
   (+ (widget-value my-number-widget) delta)))
(defun my-inc (&rest _) (my-increase 1))
(defun my-dec (&rest _) (my-increase -1))

(defun my-counter ()
  (interactive)
  (pop-to-buffer "*my counter*")
  (kill-all-local-variables)
  (let ((inhibit-read-only t))
    (erase-buffer))
  (remove-overlays)
  (setq-local my-number-widget
              (widget-create 'number
                             :size 10
                             :value 0))
  (widget-insert " ")
  (widget-create 'push-button
                 :notify 'my-dec
                 :keymap my-push-button-map ;;support double and triple down
                 "Decrement")
  (widget-insert " ")
  (widget-create 'push-button
                 :notify 'my-inc
                 :keymap my-push-button-map ;;support double and triple down
                 "Increment")
  (widget-insert "\n")
  (use-local-map widget-keymap)
  (widget-setup)
  (widget-forward 1))