;;; image.el --- image API
-;; Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
+;; Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
;; Keywords: multimedia
;; This file is part of GNU Emacs.
(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))
+ '(("\\`/[\t\n\r ]*\\*.*XPM.\\*/" . xpm)
+ ("\\`P[1-6]" . pbm)
+ ("\\`GIF8" . gif)
+ ("\\`\211PNG\r\n" . png)
+ ("\\`[\t\n\r ]*#define" . xbm)
+ ("\\`\\(MM\0\\*\\|II\\*\0\\)" . tiff)
+ ("\\`[\t\n\r ]*%!PS" . postscript)
+ ("\\`\xff\xd8" . (image-jpeg-p . jpeg)))
"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.")
+be of image type IMAGE-TYPE if IMAGE-TYPE is a symbol. If not a symbol,
+IMAGE-TYPE must be a pair (PREDICATE . TYPE). PREDICATE is called
+with one argument, a string containing the image data. If PREDICATE returns
+a non-nil value, TYPE is the image's type ")
+
+
+(defun image-jpeg-p (data)
+ "Value is non-nil if DATA, a string, consists of JFIF image data."
+ (when (string-match "\\`\xff\xd8" data)
+ (catch 'jfif
+ (let ((len (length data)) (i 2))
+ (while (< i len)
+ (when (/= (aref data i) #xff)
+ (throw 'jfif nil))
+ (setq i (1+ i))
+ (when (>= (+ i 2) len)
+ (throw 'jfif nil))
+ (let ((nbytes (+ (lsh (aref data (+ i 1)) 8)
+ (aref data (+ i 2))))
+ (code (aref data i)))
+ (when (and (>= code #xe0) (<= code #xef))
+ ;; APP0 LEN1 LEN2 "JFIF\0"
+ (throw 'jfif
+ (string-match "JFIF" (substring data i (+ i nbytes)))))
+ (setq i (+ i 1 nbytes))))))))
;;;###autoload
(while (and types (null type))
(let ((regexp (car (car types)))
(image-type (cdr (car types))))
- (when (string-match regexp data)
+ (when (or (and (symbolp image-type)
+ (string-match regexp data))
+ (and (consp image-type)
+ (funcall (car image-type) data)
+ (setq image-type (cdr image-type))))
(setq type image-type))
(setq types (cdr types))))
type))