merchant

Merchant backend to process payments, run by merchants
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taler-merchant-httpd_qr.c (3152B)

      1 /*
      2   This file is part of TALER
      3   Copyright (C) 2020 Taler Systems SA
      4 
      5   TALER is free software; you can redistribute it and/or modify it under the
      6   terms of the GNU General Public License as published by the Free Software
      7   Foundation; either version 3, or (at your option) any later version.
      8 
      9   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
     10   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
     11   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
     12 
     13   You should have received a copy of the GNU General Public License along with
     14   TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
     15 */
     16 /**
     17  * @file taler-merchant-httpd_qr.c
     18  * @brief logic to create QR codes in HTML
     19  * @author Christian Grothoff
     20  */
     21 #include "platform.h"
     22 #include <gnunet/gnunet_util_lib.h>
     23 #include <qrencode.h>
     24 #include <taler-merchant-httpd_qr.h>
     25 
     26 /**
     27  * Create the HTML for a QR code for a URI.
     28  *
     29  * @param uri input string to encode
     30  * @return NULL on error, encoded URI otherwise
     31  */
     32 char *
     33 TMH_create_qrcode (const char *uri)
     34 {
     35   QRinput *qri;
     36   QRcode *qrc;
     37   struct GNUNET_Buffer buf = { 0 };
     38 
     39   qri = QRinput_new2 (0,
     40                       QR_ECLEVEL_M);
     41   if (NULL == qri)
     42   {
     43     GNUNET_log_strerror (GNUNET_ERROR_TYPE_WARNING,
     44                          "QRinput_new2");
     45     return NULL;
     46   }
     47   /* first try encoding as uppercase-only alpha-numerical
     48      QR code (much smaller encoding); if that fails, also
     49      try using binary encoding */
     50   if ( (0 !=
     51         QRinput_append (qri,
     52                         QR_MODE_AN,
     53                         strlen (uri),
     54                         (unsigned char *) uri)) &&
     55        (0 !=
     56         QRinput_append (qri,
     57                         QR_MODE_8,
     58                         strlen (uri),
     59                         (unsigned char *) uri)) )
     60   {
     61     GNUNET_log_strerror (GNUNET_ERROR_TYPE_WARNING,
     62                          "QRinput_append");
     63     QRinput_free (qri);
     64     return NULL;
     65   }
     66   qrc = QRcode_encodeInput (qri);
     67   if (NULL == qrc)
     68   {
     69     GNUNET_log_strerror (GNUNET_ERROR_TYPE_WARNING,
     70                          "QRcode_encodeInput");
     71     QRinput_free (qri);
     72     return NULL;
     73   }
     74   QRinput_free (qri);
     75   GNUNET_buffer_write_fstr (&buf,
     76                             "<svg width='100mm' height='100mm' viewBox='0 0 %u %u' "
     77                             "version='1.1' xmlns='http://www.w3.org/2000/svg' "
     78                             "style='shape-rendering: crispedges;'>\n",
     79                             qrc->width,
     80                             qrc->width);
     81   for (unsigned int y = 0; y<(unsigned int) qrc->width; y++)
     82   {
     83     for (unsigned int x = 0; x<(unsigned int) qrc->width; x++)
     84     {
     85       unsigned int off = x + y * (unsigned int) qrc->width;
     86       if (0 == (qrc->data[off] & 1))
     87         continue;
     88       GNUNET_buffer_write_fstr (&buf,
     89                                 " <rect x=%u y=%u width=1 height=1 />\n",
     90                                 x,
     91                                 y);
     92     }
     93   }
     94   GNUNET_buffer_write_str (&buf,
     95                            "</svg>");
     96   QRcode_free (qrc);
     97   return GNUNET_buffer_reap_str (&buf);
     98 }