emacs/lisp/image.el

;;; image.el --- image API

;; Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
;; Keywords: multimedia

;; This file is part of GNU Emacs.

;; GNU Emacs 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 2, or (at your option)
;; any later version.

;; GNU Emacs 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 GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Commentary:

;;; Code:

(defconst image-type-regexps
  '(("^/\\*.*XPM.\\*/" . xpm)
    ("^P[1-6]" . pbm)
    ("^GIF8" . gif)
    ("JFIF" . jpeg)
    ("^\211PNG\r\n" . png)
    ("^#define" . xbm)
    ("^\\(MM\0\\*\\)\\|\\(II\\*\0\\)" . tiff)
    ("^%!PS" . ghostscript))
  "Alist of (REGEXP . IMAGE-TYPE) pairs used to auto-detect image types.
When the first bytes of an image file match REGEXP, it is assumed to
be of image type IMAGE-TYPE.")


;;;###autoload
(defun image-type-from-data (data)
  "Determine the image type from image data DATA.
Value is a symbol specifying the image type or nil if type cannot
be determined."
  (let ((types image-type-regexps)
	type)
    (while (and types (null type))
      (let ((regexp (car (car types)))
	    (image-type (cdr (car types))))
	(when (string-match regexp data)
	  (setq type image-type))
	(setq types (cdr types))))
    type))


;;;###autoload
(defun image-type-from-file-header (file)
  "Determine the type of image file FILE from its first few bytes.
Value is a symbol specifying the image type, or nil if type cannot
be determined."
  (unless (file-name-directory file)
    (setq file (expand-file-name file data-directory)))
  (setq file (expand-file-name file))
  (let ((header (with-temp-buffer
		  (insert-file-contents-literally file nil 0 256)
		  (buffer-string))))
    (image-type-from-data header)))


;;;###autoload
(defun image-type-available-p (type)
  "Value is non-nil if image type TYPE is available.
Image types are symbols like `xbm' or `jpeg'."
  (not (null (memq type image-types))))


;;;###autoload
(defun create-image (file-or-data &optional type data-p &rest props)
  "Create an image.
FILE-OR-DATA is an image file name or image data.
Optional TYPE is a symbol describing the image type.  If TYPE is omitted
or nil, try to determine the image type from its first few bytes
of image data.  If that doesn't work, and FILE-OR-DATA is a file name,
use its file extension.as image type.
Optional DATA-P non-nil means FILE-OR-DATA is a string containing image data.
Optional PROPS are additional image attributes to assign to the image,
like, e.g. `:heuristic-mask t'.
Value is the image created, or nil if images of type TYPE are not supported."
  (when (and (not data-p) (not (stringp file-or-data)))
    (error "Invalid image file name `%s'" file-or-data))
  (cond ((null data-p)
	 ;; FILE-OR-DATA is a file name.
	 (unless (or type
		     (setq type (image-type-from-file-header file-or-data)))
	   (let ((extension (file-name-extension file-or-data)))
	     (unless extension
	       (error "Cannot determine image type"))
	     (setq type (intern extension)))))
	(t
	 ;; FILE-OR-DATA contains image data.
	 (unless type
	   (setq type (image-type-from-data file-or-data)))))
  (unless type
    (error "Cannot determine image type"))
  (unless (symbolp type)
    (error "Invalid image type `%s'" type))
  (when (image-type-available-p type)
    (append (list 'image :type type (if data-p :data :file) file-or-data)
	    props)))


;;;###autoload
(defun put-image (image pos string &optional area)
  "Put image IMAGE in front of POS in the current buffer.
IMAGE must be an image created with `create-image' or `defimage'.
IMAGE is displayed by putting an overlay into the current buffer with a
`before-string' STRING that has a `display' property whose value is the
image.
POS may be an integer or marker.
AREA is where to display the image.  AREA nil or omitted means
display it in the text area, a value of `left-margin' means
display it in the left marginal area, a value of `right-margin'
means display it in the right marginal area."
  (let ((buffer (current-buffer)))
    (unless (eq (car image) 'image)
      (error "Not an image: %s" image))
    (unless (or (null area) (memq area '(left-margin right-margin)))
      (error "Invalid area %s" area))
    (setq string (copy-sequence string))
    (let ((overlay (make-overlay pos pos buffer))
	  (prop (if (null area) image (list (list 'margin area) image))))
      (put-text-property 0 (length string) 'display prop string)
      (overlay-put overlay 'put-image t)
      (overlay-put overlay 'before-string string))))


;;;###autoload
(defun insert-image (image string &optional area)
  "Insert IMAGE into current buffer at point.
IMAGE is displayed by inserting STRING into the current buffer
with a `display' property whose value is the image.
AREA is where to display the image.  AREA nil or omitted means
display it in the text area, a value of `left-margin' means
display it in the left marginal area, a value of `right-margin'
means display it in the right marginal area."
  (unless (eq (car image) 'image)
    (error "Not an image: %s" image))
  (unless (or (null area) (memq area '(left-margin right-margin)))
    (error "Invalid area %s" area))
  (when area
    (setq image (list (list 'margin area) image)))
  (let ((start (point)))
    (insert string)
    ;; Copy `image' so that inserting it twice in a row (adjacently)
    ;; displays two copies of the image.
    (add-text-properties start (point)
			 (list 'display (copy-sequence image)
			       'intangible (list t) ; something unique
			       'rear-nonsticky (list 'display)))))


;;;###autoload
(defun remove-images (start end &optional buffer)
  "Remove images between START and END in BUFFER.
Remove only images that were put in BUFFER with calls to `put-image'.
BUFFER nil or omitted means use the current buffer."
  (unless buffer
    (setq buffer (current-buffer)))
  (let ((overlays (overlays-in start end)))
    (while overlays
      (let ((overlay (car overlays)))
	(when (overlay-get overlay 'put-image)
	  (delete-overlay overlay)))
      (setq overlays (cdr overlays)))))


;;;###autoload
(defmacro defimage (symbol specs &optional doc)
  "Define SYMBOL as an image.

SPECS is a list of image specifications.  DOC is an optional
documentation string.

Each image specification in SPECS is a property list.  The contents of
a specification are image type dependent.  All specifications must at
least contain the properties `:type TYPE' and either `:file FILE' or
`:data DATA', where TYPE is a symbol specifying the image type,
e.g. `xbm', FILE is the file to load the image from, and DATA is a
string containing the actual image data.  The first image
specification whose TYPE is supported, and FILE exists, is used to
define SYMBOL.

Example:

   (defimage test-image ((:type xpm :file \"~/test1.xpm\")
                         (:type xbm :file \"~/test1.xbm\")))"
  (let (image)
    (while (and specs (null image))
      (let* ((spec (car specs))
	     (type (plist-get spec :type))
	     (data (plist-get spec :data))
	     (file (plist-get spec :file))
	     found)
	(when (image-type-available-p type)
	  (cond ((stringp file)
		 (let ((path load-path))
		   (while (and (not found) path)
		     (let ((try-file (expand-file-name file (car path))))
		       (when (file-readable-p try-file)
			 (setq found try-file)))
		     (setq path (cdr path)))
		   (unless found
		     (setq found (expand-file-name file data-directory)))
		   (setq image (cons 'image (plist-put spec :file found)))))
		((not (null data))
		 (setq image (cons 'image spec)))))
	(setq specs (cdr specs))))
    `(defvar ,symbol ',image ,doc)))


(provide 'image)

;;; image.el ends here