taler-merchant-httpd_qr.c (3237B)
1 /* 2 This file is part of TALER 3 Copyright (C) 2020-2026 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 src/backend/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_H); 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='100%%' height='100%%' viewBox='0 0 %u %u' " 77 "version='1.1' xmlns='http://www.w3.org/2000/svg' " 78 "aria-hidden='true' focusable='false' " 79 "style='shape-rendering: crispedges;'>\n", 80 qrc->width, 81 qrc->width); 82 for (unsigned int y = 0; y<(unsigned int) qrc->width; y++) 83 { 84 for (unsigned int x = 0; x<(unsigned int) qrc->width; x++) 85 { 86 unsigned int off = x + y * (unsigned int) qrc->width; 87 if (0 == (qrc->data[off] & 1)) 88 continue; 89 GNUNET_buffer_write_fstr (&buf, 90 " <rect x=%u y=%u width=1 height=1 />\n", 91 x, 92 y); 93 } 94 } 95 GNUNET_buffer_write_str (&buf, 96 "</svg>"); 97 QRcode_free (qrc); 98 return GNUNET_buffer_reap_str (&buf); 99 }