From 8798b229852669a021b268c13555469219ad007c Mon Sep 17 00:00:00 2001
From: Tim Vaughan <tgvaughan@gmail.com>
Date: Tue, 21 May 2019 10:03:21 +0200
Subject: [PATCH] Add start and stop chars to sixel strings, skip unknown
 chars.

---
 sixel.el | 41 +++++++++++++++++++++++------------------
 1 file changed, 23 insertions(+), 18 deletions(-)

diff --git a/sixel.el b/sixel.el
index 6626e1d..81fa32e 100644
--- a/sixel.el
+++ b/sixel.el
@@ -14,15 +14,15 @@
 ;;; Code:
 
 (defvar test-string
-  (concat "q"
+  (concat "Pq"
           "#0;2;0;0;0#1;2;100;100;0#2;2;0;100;0"
           "#1~~@@vv@@~~@@~~$"
           "#2??}}GG}}??}}??-"
-          "#1!14@"))
+          "#1!14@\\"))
 
 (defun sixel-get-params (string)
   "Retrieve the sixel parameters."
-  (car (split-string string "q")))
+  (car (split-string (substring string 2) "q")))
 
 (defun sixel-get-data (string)
   "Retrieve data string."
@@ -57,6 +57,7 @@ Returns a sixel image object."
           finished)
       (while  (not finished)
         (cond
+         ;; Define colour:
          ((looking-at "#\\([0-9]+\\);\\([0-9]+\\);\\([0-9]+\\);\\([0-9]+\\);\\([0-9]+\\)")
           (let ((tag (format "%02x" (string-to-number (match-string 1))))
                 (mode (match-string 2))
@@ -64,19 +65,19 @@ Returns a sixel image object."
                 (g (string-to-number (match-string 4)))
                 (b (string-to-number (match-string 5))))
             (push (list tag r g b) colour-map)))
-
+         ;; Set current colour:
          ((looking-at "#\\([0-9]+\\)")
           (let ((tag (format "%02x" (string-to-number (match-string 1)))))
             (setq current-colour tag)))
-
+         ;; Carriage return:
          ((looking-at "\\$")
           (setq idx-out 0))
-
+         ;; New line:
          ((looking-at "-")
           (push (reverse this-row) rows)
           (setq this-row nil)
           (setq idx-out 0))
-
+         ;; RLE sixel char sequence:
          ((looking-at "!\\([0-9]+\\)\\([?-~]\\)")
           (let ((repeat-count (string-to-number (match-string 1)))
                 (char (elt (match-string 2) 0)))
@@ -84,15 +85,17 @@ Returns a sixel image object."
               (setq this-row
                     (sixel-tag-sixel-in-row this-row idx-out char current-colour))
               (setq idx-out (1+ idx-out)))))
-
-         ((looking-at "\\([?-~]\\)")
+         ;; Sixel char:
+         ((looking-at "\\([?-~]\\)") ; Sixel char
           (let ((char (elt (match-string 1) 0)))
             (setq this-row
                   (sixel-tag-sixel-in-row this-row idx-out char current-colour))
             (setq idx-out (1+ idx-out))))
-
-         (t (setq finished t)))
-
+         ;; Termination sequence:
+         ((looking-at "\\\\")
+          (setq finished t))
+         ;; Skip other char:
+         ((looking-at "[[:ascii:]]")))
         (goto-char (match-end 0)))
       (push (reverse this-row) rows)
       (cons colour-map
@@ -172,11 +175,13 @@ of SIXEL-IMAGE."
   (let* ((param-string (sixel-get-params string))
          (data-string (sixel-get-data string))
          (sixel-image (sixel-process-data data-string)))
-    (concat
-     "/* XPM */"
-     "static char * pixmap[] = {"
-     (sixel-image-to-xpm-values sixel-image) ",\n"
-     (sixel-image-to-xpm-colours sixel-image) ",\n"
-     (sixel-image-to-xpm-pixels sixel-image) "};")))
+    (if (string-prefix-p "P" string)
+        (concat
+         "/* XPM */"
+         "static char * pixmap[] = {"
+         (sixel-image-to-xpm-values sixel-image) ",\n"
+         (sixel-image-to-xpm-colours sixel-image) ",\n"
+         (sixel-image-to-xpm-pixels sixel-image) "};")
+      (error "Incorrecly formatted sixel string."))))
 
 ;; sixel.el ends here
-- 
2.20.1