On Mon, Apr 15 2013, Andreas Schwab wrote:
> David Edmondson <dme@dme.org> writes:
>
>> That's good to know, thanks. I was surprised that I couldn't quickly
>> find a non-w3m function to do the URL decoding already in emacs. It's
>> easy to write a new one, of course, but did I miss an existing function?
>
> (url-unhex-string "%2b%2d%3d") => "+-="

Thank you. Here is an improved patch.

diff --git a/lisp/shr.el b/lisp/shr.el
index 5df5297..eaf83e2 100644
--- a/lisp/shr.el
+++ b/lisp/shr.el
@@ -593,6 +593,16 @@ size, and full-buffer size."
 		      (put-text-property start (point) type value))))))))))
     (kill-buffer image-buffer)))
 
+(defun shr-image-from-data (data)
+  "Return an image from the data: URI content DATA."
+  (when (string-match "\\(\\([^/;,]+\\(/[^;,]+\\)?\\)\\(;[^;,]+\\)*\\)?,\\(.*\\)"
+		      data)
+    (let ((param (match-string 4 data))
+	  (payload (url-unhex-string (match-string 5 data))))
+      (when (string-match "^.*\\(;[ \t]*base64\\)$" param)
+	(setq payload (base64-decode-string payload)))
+      payload)))
+
 (defun shr-put-image (data alt &optional flags)
   "Put image DATA with a string ALT.  Return image."
   (if (display-graphic-p)
@@ -983,6 +993,12 @@ ones, in case fg and bg are nil."
 	  ;; Ignore zero-sized or single-pixel images.
 	  )
 	 ((and (not shr-inhibit-images)
+	       (string-match "\\`data:" url))
+	  (let ((image (shr-image-from-data (substring url (match-end 0)))))
+	    (if image
+		(funcall shr-put-image-function image alt)
+	      (insert alt))))
+	 ((and (not shr-inhibit-images)
 	       (string-match "\\`cid:" url))
 	  (let ((url (substring url (match-end 0)))
 		image)