DocViewMode で画像がバッファのサイズにフィットするように拡張

皆様， DocViewMode 使ってますか?
Emacs で PDF やら PS ファイルが見れちゃう便利 Elisp ですね．
Emacs 23 なら普通に \C-x\C-f (find-file) で開くだけで起動しちゃいます．

レポート作成を WYSIWYG-TeX.el (使ってね!!!) でしている時とかにもの凄くお世話になるモードなんですが，残念ながらページに画像をフィットさせる機能がありません．．．

なければ作ればいいじゃん!

ってなことで作ってみました．
名づけて Fit-to-page extension for DocViewMode !! いえい!!!

次期バージョンアップの際の提案として，勝手に EmacsWiki に書いたり作者様にメールをお送りしたりしましたが，ここでもコードと使い方を掲載しておきます．

以下のコードを .emacs に追加

;;; Fit-to-page extension for DocView-mode
(require 'doc-view)

(defconst doc-view-tmp-png-path "/tmp/doc-view-tmp.png")
(defconst doc-view-tmp-pdf/ps-path "/tmp/doc-view-tmp-img")

(defun doc-view-get-dpi ()
  "Returns resolution of your display in Dpi.
If you don't use X Window System, this function asks you Dpi."
  (let ((resolution-info (shell-command-to-string
                          "xdpyinfo |grep 'resolution'")))
    (if (string-match "\\([0-9]+\\)x" resolution-info)
        (string-to-number (match-string 1 resolution-info))
      (read-number "Input your display resolution (Dpi): "))))

(defun doc-view-pdf/ps-size-in-px (pdf/ps-path)
  "Returns (width . height) of PDF/PS file with 'pdf/ps-path`"
  (call-process "gs" nil nil t
                "-dSAFER" "-dNOPAUSE" "-sDEVICE=png16m" "-dTextAlphaBits=4"
                "-dBATCH" "-dGraphicsAlphaBits=4" "-dQUIET"
                "-dFirstPage=1" "-dLastPage=1" (concat "-sOutputFile=" doc-view-tmp-png-path)
                pdf/ps-path)
  (cons (string-to-number
         (shell-command-to-string
          (concat "echo -n `identify -format \"%w\" " doc-view-tmp-png-path "`")))
        (string-to-number
         (shell-command-to-string
          (concat "echo -n `identify -format \"%h\" " doc-view-tmp-png-path "`")))))

(defun doc-view-window-size-in-px ()
  "Returns current window size in pixel like (width . height) ."
  (cons (* (window-width) (frame-char-width))
        (* (window-height) (frame-char-height))))

(defun doc-view-px-to-natural (px dpi)
  "Convert pixel to \"Natural size\", which is about the same size with one printed on paper.
Emacs displays images with \"Natural size\", so this conversion is necessary."
  (* px 1.3871979865e-2 dpi))

(defun doc-view-percentage-to-fit (pdf/ps-path dpi)
  "Returns percentage you can set to fit image onto a window.
For example, (88 . 74) means if you set 88 to 'doc-view-resolution',
the width of the image fits the window."
  (let* ((pdf/ps-size (doc-view-pdf/ps-size-in-px pdf/ps-path))
         (pdf/ps-width (car pdf/ps-size))
         (pdf/ps-height (cdr pdf/ps-size))
         (window-size (doc-view-window-size-in-px))
         (window-width (car window-size))
         (window-height (cdr window-size)))
    (cons (* 100.0 (/ window-width (doc-view-px-to-natural (float pdf/ps-width) dpi)))
          (* 100.0 (/ window-height (doc-view-px-to-natural (float pdf/ps-height) dpi))))))

(defun doc-view-change-size (size)
  "Changes the size of the image viewed in DocViewMode into 'size'."
  (set (make-local-variable 'doc-view-resolution) size)
  (doc-view-reconvert-doc))

(defun doc-view-fit-height ()
  "Makes the height of image fit with window."
  (interactive)
  (doc-view-change-size
   (round (cdr (doc-view-percentage-to-fit (buffer-file-name) (doc-view-get-dpi))))))
(defun doc-view-fit-width ()
  "Makes the height of image fit with window."
  (interactive)
  (doc-view-change-size
   (round (car (doc-view-percentage-to-fit (buffer-file-name) (doc-view-get-dpi))))))
(defun doc-view-fit-page ()
  "Makes image fit with window."
  (interactive)
  (let ((percentage (doc-view-percentage-to-fit (buffer-file-name) (doc-view-get-dpi))))
    (doc-view-change-size (round (min (car percentage)
                             (cdr percentage))))))


;; キーマップはお好きにカスタマイズしてください．
(add-hook 'doc-view-mode-hook
          '(lambda ()
             (local-set-key "f" 'doc-view-fit-page)
             (local-set-key "w" 'doc-view-fit-width)
             (local-set-key "h" 'doc-view-fit-height)))