generateQR() method data loss fix

Added regression parameterized test for Structure Append mode

final_qr_code clear outside generateQR() method

modules/objdetect/src/qrcode_encoder.cpp

@@ -332,14 +332,16 @@ void QRCodeEncoderImpl::generateQR(const std::string &input)
         }
         total_num = (uint8_t) struct_num - 1;
     }
-    int segment_len = (int) ceil((int) input.length() / struct_num);
 
-    for (int i = 0; i < struct_num; i++)
+    auto string_itr = input.begin();
+    for (int i = struct_num; i > 0; --i)
     {
         sequence_num = (uint8_t) i;
-        int segment_begin = i * segment_len;
-        int segemnt_end = min((i + 1) * segment_len, (int) input.length()) - 1;
-        std::string input_info = input.substr(segment_begin, segemnt_end - segment_begin + 1);
+        size_t segment_begin = string_itr - input.begin();
+        size_t segment_end = (input.end() - string_itr) / i;
+
+        std::string input_info = input.substr(segment_begin, segment_end);
+        string_itr += segment_end;
         int detected_version = versionAuto(input_info);
         CV_Assert(detected_version != -1);
         if (version_level == 0)
@@ -349,7 +351,6 @@ void QRCodeEncoderImpl::generateQR(const std::string &input)
 
         payload.clear();
         payload.reserve(MAX_PAYLOAD_LEN);
-        final_qrcodes.clear();
         format = vector<uint8_t> (15, 255);
         version_reserved = vector<uint8_t> (18, 255);
         version_size = (21 + (version_level - 1) * 4);
@@ -1234,6 +1235,7 @@ void QRCodeEncoderImpl::encode(const String& input, OutputArray output)
     generateQR(input);
     CV_Assert(!final_qrcodes.empty());
     output.assign(final_qrcodes[0]);
+    final_qrcodes.clear();
 }
 
 void QRCodeEncoderImpl::encodeStructuredAppend(const String& input, OutputArrayOfArrays output)
@@ -1250,6 +1252,7 @@ void QRCodeEncoderImpl::encodeStructuredAppend(const String& input, OutputArrayO
     {
         output.getMatRef(i) = final_qrcodes[i];
     }
+    final_qrcodes.clear();
 }
 
 Ptr<QRCodeEncoder> QRCodeEncoder::create(const QRCodeEncoder::Params& parameters)

modules/objdetect/test/test_qrcode_encode.cpp

@@ -450,6 +450,32 @@ TEST(Objdetect_QRCode_Encode_Decode_Structured_Append, DISABLED_regression)
 
 #endif // UPDATE_QRCODE_TEST_DATA
 
+CV_ENUM(EncodeModes, QRCodeEncoder::EncodeMode::MODE_NUMERIC,
+                     QRCodeEncoder::EncodeMode::MODE_ALPHANUMERIC,
+                     QRCodeEncoder::EncodeMode::MODE_BYTE)
+
+typedef ::testing::TestWithParam<EncodeModes> Objdetect_QRCode_Encode_Decode_Structured_Append_Parameterized;
+TEST_P(Objdetect_QRCode_Encode_Decode_Structured_Append_Parameterized, regression_22205)
+{
+    const std::string input_data = "the quick brown fox jumps over the lazy dog";
+
+    std::vector<cv::Mat> result_qrcodes;
+
+    cv::QRCodeEncoder::Params params;
+    int encode_mode = GetParam();
+    params.mode = static_cast<cv::QRCodeEncoder::EncodeMode>(encode_mode);
+
+    for(size_t struct_num = 2; struct_num < 5; ++struct_num)
+    {
+        params.structure_number = static_cast<int>(struct_num);
+        cv::Ptr<cv::QRCodeEncoder> encoder = cv::QRCodeEncoder::create(params);
+        encoder->encodeStructuredAppend(input_data, result_qrcodes);
+        EXPECT_EQ(result_qrcodes.size(), struct_num) << "The number of QR Codes requested is not equal"<<
+                                                    "to the one returned";
+    }
+}
+INSTANTIATE_TEST_CASE_P(/**/, Objdetect_QRCode_Encode_Decode_Structured_Append_Parameterized, EncodeModes::all());
+
 TEST(Objdetect_QRCode_Encode_Decode, regression_issue22029)
 {
     const cv::String msg = "OpenCV";