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;;; image.el --- image API

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;; Copyright (C) 1998, 1999 Free Software Foundation, Inc.
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;; Keywords: multimedia
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;; 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
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(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
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be determined."
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  (let ((types image-type-regexps)
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	type)
    (while (and types (null type))
      (let ((regexp (car (car types)))
	    (image-type (cdr (car types))))
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	(when (string-match regexp data)
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	  (setq type image-type))
	(setq types (cdr types))))
    type))


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;;;###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)))


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;;;###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
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(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.
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Optional TYPE is a symbol describing the image type.  If TYPE is omitted
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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.
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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."
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  (unless (stringp file-or-data)
    (error "Invalid image file name or data `%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"))
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  (unless (symbolp type)
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    (error "Invalid image type `%s'" type))
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  (when (image-type-available-p type)
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    (append (list 'image :type type (if data-p :data :file) file-or-data)
	    props)))
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;;;###autoload
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(defun put-image (image pos string &optional area)
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  "Put image IMAGE in front of POS in the current buffer.
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IMAGE must be an image created with `create-image' or `defimage'.
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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.
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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'
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means display it in the right marginal area."
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  (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))
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    (setq string (copy-sequence string))
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    (let ((overlay (make-overlay pos pos buffer))
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	  (prop (if (null area) image (list (list 'margin area) image))))
      (put-text-property 0 (length string) 'display prop string)
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      (overlay-put overlay 'put-image t)
      (overlay-put overlay 'before-string string))))
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;;;###autoload
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(defun insert-image (image string &optional area)
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  "Insert IMAGE into current buffer at point.
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IMAGE is displayed by inserting STRING into the current buffer
with a `display' property whose value is the image.
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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'
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means display it in the right marginal area."
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  (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))
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  (when area
    (setq image (list (list 'margin area) image)))
  (let ((start (point)))
    (insert string)
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    ;; Copy `image' so that inserting it twice in a row (adjacently)
    ;; displays two copies of the image.
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    (add-text-properties start (point)
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			 (list 'display (copy-sequence image)
			       'intangible (list t) ; something unique
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			       'rear-nonsticky (list 'display)))))
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;;;###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)
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	  (delete-overlay overlay)))
      (setq overlays (cdr overlays)))))
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;;;###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
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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.
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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))
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	     (data (plist-get spec :data))
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	     (file (plist-get spec :file)))
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	(when (image-type-available-p type)
	  (cond ((stringp file)
		 (setq file (expand-file-name file data-directory))
		 (when (file-readable-p file)
		   (setq image (cons 'image (plist-put spec :file file)))))
		((stringp data)
		 (setq image (cons 'image spec)))))
	(setq specs (cdr specs))))
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    `(defvar ,symbol ',image ,doc)))


(provide 'image)

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;;; image.el ends here