Add SVG support

README.org

@@ -21,9 +21,10 @@
   qrencode RET=.
 
   QR Codes are rendered as Unicode text, but there is an option to
-  export them as bitmap (NetPBM format) by pressing =e= in the QR Code
-  buffer.  There are also some public elisp library functions to
-  generate QR Codes for use in other elisp code.
+  export them as bitmap (NetPBM format) or vector graphics (SVG) by
+  pressing =e= in the QR Code buffer.  There are also some public
+  elisp library functions to generate QR Codes for use in other elisp
+  code.
 
   Currently two NetPBM formats are supported: P1 and P4.  The latter
   is much smaller and the exporter much faster, so highly recommended.
@@ -32,6 +33,10 @@
   format can be changed.  In the next major version release P1 support
   is likely to get dropped in favour of P4.
 
+  SVG export is available if =svg.el= (Emacs 26.1 or newer) is
+  available.  This can be selected by customizing
+  =qrencode-export-format= to ='svg=.
+
 *** Converting different bitmaps
 
   This package only supports exporting to NetPBM format due to the
@@ -60,7 +65,7 @@
 
    [[file:https://github.com/ruediger/qrencode-el/actions/workflows/test.yml/badge.svg]]
 
-  The code is written in pure Emacs Lisp on GNU Emacs 27.  It should
+  The code is written in pure Emacs Lisp on GNU Emacs 31.  It should
   be backwards compatible to GNU Emacs 25.1 and potentially even
   earlier with =seq= and =cl-lib= compat libraries.
 

qrencode-tests.el

@@ -536,6 +536,13 @@ The expected word for version 7 is the literal from section 7.10 of the
 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
 ")))
 
+(ert-deftest qrencode-svg-path-test ()
+  "Test SVG path."
+  (skip-unless (featurep 'svg))
+  (should (string= (qrencode--svg-path [[0 0] [0 0]] 0) ""))
+  (should (string= (qrencode--svg-path [[1 1] [1 1]] 0) "M0 0h2v1h-2zM0 1h2v1h-2z"))
+  (should (string= (qrencode--svg-path [[0 0 1] [0 1 1] [0 0 0]] 0) "M2 0h1v1h-1zM1 1h2v1h-2z")))
+
 (defun qrencode-tests--get-file (filename)
   "Helper function returning contents of FILENAME."
   (with-temp-buffer
@@ -553,7 +560,8 @@ The expected word for version 7 is the literal from section 7.10 of the
     (should (not (null qrencode--raw-qr)))
     (let ((tmpfile-p1 (make-temp-file "qr-p1" nil ".pbm"))
           (tmpfile-p4 (make-temp-file "qr-p4" nil ".pbm"))
-          p1 p4)
+          (tmpfile-svg (make-temp-file "qr-svg" nil ".svg"))
+          p1 p4 svg)
       (unwind-protect
           (progn
             (let ((qrencode-export-format 'p1))
@@ -564,18 +572,26 @@ The expected word for version 7 is the literal from section 7.10 of the
               (qrencode-export-buffer-to-file tmpfile-p4))
             (setq p4 (qrencode-tests--get-file tmpfile-p4))
             (should (string-prefix-p "P4\n" p4))
+            (when (featurep 'svg)
+              (let ((qrencode-export-format 'svg))
+                (qrencode-export-buffer-to-file tmpfile-svg))
+              (setq svg (qrencode-tests--get-file tmpfile-svg))
+              (should (string-prefix-p "<svg " svg)))
             ;; TODO: test sizes.
             ;; TODO: test pixel equivalence between P1 and P4.
             )
         (delete-file tmpfile-p1)
-        (delete-file tmpfile-p4)))))
+        (delete-file tmpfile-p4)
+        (delete-file tmpfile-svg)))))
 
 (ert-deftest qrencode-zbarimg-test ()
   "Test decoding generated QRCodes using the zbarimg program."
   (let ((zbarimg (executable-find "zbarimg")))
     (skip-unless zbarimg)
     (let ((tmpfile-p1 (make-temp-file "qr-p1" nil ".pbm"))
-          (tmpfile-p4 (make-temp-file "qr-p4" nil ".pbm")))
+          (tmpfile-p4 (make-temp-file "qr-p4" nil ".pbm"))
+          (tmpfile-svg (make-temp-file "qr-svg" nil ".svg"))
+          qr)
       (unwind-protect
           (cl-loop for input across
                    ["hello"
@@ -588,14 +604,19 @@ The expected word for version 7 is the literal from section 7.10 of the
                     ;; raw UTF-8 characters
                     "😸🚗愛"
                     ]
-                   do (qrencode--write-as-netpbm-p4 tmpfile-p4 (qrencode input nil nil 'return-raw))
+                   do (setq qr (qrencode input nil nil 'return-raw))
+                   do (qrencode--write-as-netpbm-p4 tmpfile-p4 qr)
                    do (with-temp-file tmpfile-p1
-                        (insert (qrencode-format-as-netpbm (qrencode input nil nil 'return-raw))))
-                   do (dolist (tmpfile (list tmpfile-p1 tmpfile-p4))
-                        (should (string= (shell-command-to-string (format "%s -q '%s'" zbarimg tmpfile))
-                                         (format "QR-Code:%s\n" input)))))
+                        (insert (qrencode-format-as-netpbm qr)))
+                   do (when (featurep 'svg)
+                        (qrencode--write-as-svg tmpfile-svg qr))
+                   do (dolist (tmpfile (list tmpfile-p1 tmpfile-p4 (when (featurep 'svg) tmpfile-svg)))
+                        (when tmpfile
+                         (should (string= (shell-command-to-string (format "%s -q '%s'" zbarimg tmpfile))
+                                          (format "QR-Code:%s\n" input))))))
         (delete-file tmpfile-p1)
-        (delete-file tmpfile-p4)))))
+        (delete-file tmpfile-p4)
+        (delete-file tmpfile-svg)))))
 
 (provide 'qrencode-tests)
 ;;; qrencode-tests.el ends here

qrencode.el

@@ -4,7 +4,7 @@
 
 ;; Author: Rüdiger Sonderfeld <ruediger@c-plusplus.net>
 ;; Keywords: qrcode comm
-;; Version: 1.5
+;; Version: 1.6-beta1
 ;; Package-Requires: ((emacs "25.1"))
 ;; Package: qrencode
 ;; URL: https://github.com/ruediger/qrencode-el
@@ -44,6 +44,9 @@
 (require 'seq)
 (require 'thingatpt)
 
+;; svg.el is only available in Emacs 26.1 and newer.
+(require 'svg nil 'noerror)
+
 ;;; Error correction
 ;; Reed solomon ECC implementation based on https://research.swtch.com/field
 
@@ -1043,6 +1046,61 @@ Optionally specify PIXEL-SIZE (default is 3)."
      (dotimes (_ quiet-zone-size)
        (dotimes (_ bsize) (insert 0))))))
 
+;; Declare SVG functions in case svg.el is not available.
+(declare-function svg-create "svg" (width height &rest args))
+(declare-function svg-rectangle "svg" (svg x y width height &rest args))
+(declare-function svg-node "svg" (svg tag &rest args))
+(declare-function svg-print "svg" (dom))
+
+(defun qrencode--svg-path (qr quiet-zone-size)
+  "Return svg path for QR with QUIET-ZONE-SIZE."
+  (with-temp-buffer
+    (let ((size (length qr)))
+      (dotimes (r size)
+        (let ((c 0))
+          (while (< c size)
+            (if (= (qrencode--aaref qr c r) 1)
+                (let ((start c))
+                  ;; We only bother scanning one row at a time and turning
+                  ;; series of 1's into a rectangle.
+                  (while (and (< c size) (= (qrencode--aaref qr c r) 1))
+                    (setq c (1+ c)))
+                  (let ((block-len (- c start)))
+                    (insert
+                     ;; `Mx y` move to x,y absolute
+                     ;; `hx` draw x horizontal relative
+                     ;; `v1` draw 1 vertical relative
+                     ;; `z` close
+                     (format "M%d %dh%dv1h-%dz"
+                             (+ start quiet-zone-size)
+                             (+ r quiet-zone-size)
+                             block-len
+                             block-len))))
+              (setq c (1+ c)))))))
+    (buffer-string)))
+
+(defun qrencode-as-svg (qr &optional pixel-size inverse)
+  "Return an svg object of QR code.
+See documentation of svg.el for how to use the object.
+Optional argument PIXEL-SIZE (default is 3) and INVERSE to flip white/dark mode."
+  (let* ((size (length qr))
+         (quiet-zone-size 4)
+         (pixel-size (or pixel-size 3))
+         (size-wqz (+ quiet-zone-size size quiet-zone-size))
+         (width-height (* size-wqz pixel-size))
+         (background-colour (if inverse "#000" "#fff"))
+         (fill-colour (if inverse "#fff" "#000"))
+         (svgimg (svg-create width-height width-height :viewBox (format "0 0 %d %d" size-wqz size-wqz))))
+    (svg-rectangle svgimg 0 0 size-wqz size-wqz :fill background-colour)  ;; background
+    (svg-node svgimg 'path :d (qrencode--svg-path qr quiet-zone-size) :fill fill-colour)
+    svgimg))
+
+(defun qrencode--write-as-svg (filename qr &optional pixel-size)
+  "Write QR as svg to FILENAME."
+  (with-temp-file filename
+    (svg-print (qrencode-as-svg qr pixel-size))
+    (insert "\n")))
+
 (defgroup qrencode nil
   "QREncode: Encoder for QR Codes."
   :link '(url-link "https://github.com/ruediger/qrencode-el")
@@ -1073,9 +1131,10 @@ bitmap format."
 P1 is the current default.  But P4 export is much faster and produces
 smaller (binary) files.  In the next major release the default will
 change to P4 and P1 support will be removed."
-  :type '(choice
+  :type `(choice
           (const :tag "NetPBM text (P1)" p1)
-          (const :tag "NetPBM binary (P4)" p4))
+          (const :tag "NetPBM binary (P4)" p4)
+          ,@(when (featurep 'svg) '((const :tag "SVG" svg))))
   :package-version '(qrencode . "1.5-beta4")
   :group 'qrencode)
 
@@ -1094,6 +1153,8 @@ change to P4 and P1 support will be removed."
       (error "No raw QRCode data found")
     (let ((qr qrencode--raw-qr))       ; save ref to buffer local var.
       (pcase qrencode-export-format
+        ((and 'svg (guard (featurep 'svg)))
+         (qrencode--write-as-svg filename qr qrencode-export-pixel-size))
         ('p4
          (qrencode--write-as-netpbm-p4 filename qr qrencode-export-pixel-size))
         ((or 'p1 'nil)