added QrCodeBot example

This example shows how to program a Telegram Bot that can generate QrCode images from text and extract text from QrCode Images.

README.md

@@ -27,6 +27,7 @@ see [examples](examples/) for more:
 |:--------------------------------------------|:-------------------------------------------------------------------------------------------------------------------------------------------------------|:------------------------------------------------------------------------------:|
 | [WeatherBot](examples/WeatherBot)           | This example shows how to program a Telegram Bot that displays the weather information of a city using the [weather api](https://www.weatherapi.com/). |   <img src="examples/WeatherBot/img/preview.jpg" alt="preview" width="200">    |
 | [EarthquakeBot](examples/EarthquakeBot)     | This example shows how to program a Telegram Bot that will alert you if there is a recent earthquake somewhere in the world.                           |  <img src="examples/EarthquakeBot/img/alerts.jpg" alt="preview" width="200">   |
+| [QrCodeBot](examples/QrCodeBot) | This example shows how to program a Telegram Bot that can generate QrCode images from text and extract text from QrCode Images.                        |    <img src="examples/QrCodeBot/img/encode.jpg" alt="preview" width="200">     |
 | [UrlShortenerBot](examples/UrlShortenerBot) | This example shows how to program Telegram Bot for shortening URLs.                                                                                    | <img src="examples/UrlShortenerBot/img/preview.jpg" alt="preview" width="200"> |
 | [Buttons](examples/Buttons)                 | This example shows how to program a basic Telegram Bot that uses inline keyboard buttons to interact with users.                                       |     <img src="examples/Buttons/img/preview.jpg" alt="preview" width="200">     |
 

examples/QrCodeBot/CMakeLists.txt

@@ -0,0 +1,30 @@
+cmake_minimum_required(VERSION 3.10)
+project(qrcode_bot)
+
+set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+include(FetchContent)
+FetchContent_Declare(tgbotxx
+        GIT_REPOSITORY "https://github.com/baderouaich/tgbotxx"
+        GIT_TAG main
+        )
+FetchContent_MakeAvailable(tgbotxx)
+
+# Qr Code Processing Library
+FetchContent_Declare(ZXing
+        GIT_REPOSITORY "https://github.com/zxing-cpp/zxing-cpp"
+        GIT_TAG master
+        )
+FetchContent_MakeAvailable(ZXing)
+
+# Stb libs for image read/write
+FetchContent_Declare(stb
+        GIT_REPOSITORY https://github.com/nothings/stb.git
+        GIT_TAG master
+)
+FetchContent_MakeAvailable(stb)
+
+add_executable(${PROJECT_NAME} main.cpp)
+target_link_libraries(${PROJECT_NAME} PUBLIC tgbotxx ZXing)
+target_include_directories(${PROJECT_NAME} PUBLIC ${stb_SOURCE_DIR})

examples/QrCodeBot/README.md

@@ -0,0 +1,22 @@
+## QR Code Bot
+This example shows how to program a Telegram Bot that can generate QrCode images from text and extract text from QrCode Images.
+
+### Run
+```bash
+mkdir build && cd build
+cmake .. -DCMAKE_BUILD_TYPE=Release
+make -j8
+./qrcode_bot YOUR_BOT_TOKEN
+```
+
+### How to create a new Bot and obtain its private token ?
+1. Open the Telegram mobile app and search BotFather
+2. Send BotFather a command /newbot
+3. Follow instructions to create a new Bot
+4. After you finish the instructions, you will receive a Bot Token, make sure you keep it secured.
+
+### Encode (Text to QRCode Image)
+<img src="img/encode.jpg" alt="Encode" width="300"/>
+
+### Decode (QRCode Image to Text)
+<img src="img/decode.jpg" alt="Decode" width="300"/>

examples/QrCodeBot/main.cpp

@@ -0,0 +1,149 @@
+#include <csignal> // std::signal
+#include <string>
+#include <tgbotxx/tgbotxx.hpp> // tgbotxx
+using namespace tgbotxx;
+
+#include <BarcodeFormat.h>
+#include <BitMatrix.h>
+#include <CharacterSet.h>
+#include <GTIN.h>
+#include <MultiFormatWriter.h>
+#include <ReadBarcode.h>
+
+#define STB_IMAGE_IMPLEMENTATION
+#include <stb_image.h>
+#define STB_IMAGE_WRITE_IMPLEMENTATION
+#include <stb_image_write.h>
+
+class QrCodeBot : public Bot {
+  public:
+    QrCodeBot(const std::string& token) : Bot(token) {}
+
+  private:
+    void onStart() override {
+      // Drop pending updates
+      api()->deleteWebhook(true);
+
+      // Register my commands
+      Ptr<BotCommand> startCmd(new BotCommand());
+      startCmd->command = "/start";
+      startCmd->description = "Start interacting with the bot";
+      api()->setMyCommands({startCmd});
+
+      std::cout << "Bot " << api()->getMe()->username << " Started\n";
+    }
+
+    void onStop() override {
+      std::cout << "\nStopping Bot. Please wait...\n";
+    }
+
+    void onNonCommandMessage(const Ptr<Message>& message) override try {
+      if (not message->photo.empty()) { // Did user send a photo ?
+        // Convert QrCode image to text
+        api()->sendChatAction(message->chat->id, "typing");
+        std::string qrCodeText = extractTextFromQrCodeImage(message->photo);
+        api()->sendMessage(message->chat->id, qrCodeText);
+      } else if (not message->text.empty()) { // Did user send a text ?
+        // Convert text to QrCode image
+        api()->sendChatAction(message->chat->id, "upload_photo");
+        cpr::File qrCodePhoto = convertTextToQrCodeImage(message->text);
+        api()->sendPhoto(message->chat->id, qrCodePhoto);
+      }
+    } catch (const std::exception& e) {
+      std::cerr << e.what() << std::endl;
+      api()->sendMessage(message->chat->id, "Internal error");
+    }
+
+    void onCommand(const Ptr<Message>& message) override {
+      if (message->text == "/start") {
+        api()->sendMessage(message->chat->id, "Welcome to QrCodeBot! Please send a text to generate a QrCode Image, or send a QrCode Image to extract text from it.");
+      }
+    }
+
+  protected:
+    /// Extracts UTF-8 text from a QR Code Image
+    /// @param photos multiple resolution photo sizes from Message
+    /// @returns Extracted UTF-8 text from the QR Code image
+    std::string extractTextFromQrCodeImage(const std::vector<Ptr<PhotoSize>>& photos) {
+      // Get the highest resolution image (Telegram provides 4 resolutions of photo sent by user)
+      const Ptr<PhotoSize>& photo = *std::max_element(photos.begin(), photos.end(), [](const Ptr<PhotoSize>& A, const Ptr<PhotoSize>& B) {
+        return A->height < B->height && A->width < B->width;
+      });
+
+      // Download photo from Telegram servers
+      Ptr<File> file = api()->getFile(photo->fileId);
+      std::string bytes = api()->downloadFile(file->filePath, [](long total, long downloaded) -> bool {
+        std::cout << "Downloading photo " << downloaded << '/' << total << " bytes     \r" << std::flush;
+        return true;
+      });
+      std::cout << std::endl;
+
+      // Save downloaded photo to ./photos/input/PHOTO.jpg
+      fs::path photosDir = "photos/input";
+      if (!fs::exists(photosDir)) fs::create_directory(photosDir);
+      fs::path photoPath = photosDir / fs::path(file->filePath).filename();
+      std::ofstream ofs{photoPath, std::ios::binary};
+      ofs.write(bytes.data(), bytes.size());
+      ofs.close();
+      bytes.clear();
+
+      // Load back image using stbi image
+      int width{}, height{}, channels{};
+      std::unique_ptr<stbi_uc, void (*)(void *)> buffer(stbi_load(photoPath.string().c_str(), &width, &height, &channels, 3), stbi_image_free);
+      if (!buffer) {
+        throw Exception("Failed to read image: " + photoPath.string());
+      }
+
+      // Decode qr code image
+      ZXing::DecodeHints hints{};
+      hints.setTextMode(ZXing::TextMode::HRI); // Human Readable Interpretation
+      hints.setEanAddOnSymbol(ZXing::EanAddOnSymbol::Read);
+      hints.setTryHarder(true);
+      ZXing::ImageView image{buffer.get(), width, height, ZXing::ImageFormat::RGB};
+      auto result = ZXing::ReadBarcode(image, hints);
+      if (result.isValid()) {
+        return result.text();
+      }
+      return ZXing::ToString(result.error());
+    }
+
+    /// Converts @text to a QR Code image
+    /// @param text UTF-8 Text to convert
+    /// @returns cpr::File filename of the generated image
+    cpr::File convertTextToQrCodeImage(const std::string& text) {
+      ZXing::MultiFormatWriter writer(ZXing::BarcodeFormat::QRCode);
+      writer.setMargin(-1);
+      writer.setEncoding(ZXing::CharacterSet::UTF8);
+      ZXing::BitMatrix matrix = writer.encode(text, 128, 128);
+      ZXing::Matrix<std::uint8_t> bitmap = ZXing::ToMatrix<std::uint8_t>(matrix);
+
+      fs::path photosDir = "photos/output";
+      if (!fs::exists(photosDir)) fs::create_directories(photosDir);
+      fs::path photoPath = photosDir / (std::to_string(std::time(nullptr)) + ".jpg");
+      // int success = stbi_write_png(filePath.c_str(), bitmap.width(), bitmap.height(), 1, bitmap.data(), 0);
+      int success = stbi_write_jpg(photoPath.c_str(), bitmap.width(), bitmap.height(), 1, bitmap.data(), 0);
+      if (!success) {
+        throw Exception("Failed to write image: " + photoPath.string());
+      }
+      return cpr::File(photoPath.string());
+    }
+};
+
+
+int main(int argc, const char *argv[]) {
+  if (argc < 2) {
+    std::cerr << "Usage:\nqrcode_bot \"BOT_TOKEN\"\n";
+    return EXIT_FAILURE;
+  }
+  static std::unique_ptr<QrCodeBot> BOT;
+  std::signal(SIGINT, [](int) { // Graceful Bot exit on CTRL+C
+    if (BOT) {
+      BOT->stop();
+    }
+    std::exit(EXIT_SUCCESS);
+  });
+
+  BOT = std::make_unique<QrCodeBot>(argv[1]);
+  BOT->start();
+  return EXIT_SUCCESS;
+}