vendor: OpenCV 5.0.0 snapshot at 755e50675d97db9b7d449d8bd6b09888646f6c6e

2026-08-22 00:11:13 +08:00
commit 12022378a3
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+/**
+ * @file read_write_attributes.cpp
+ * @author Fangjun Kuang <csukuangfj dot at gmail dot com>
+ * @date December 2017
+ *
+ * @brief It demonstrates how to read and write attributes inside the
+ * root group.
+ *
+ * Currently, only the following datatypes can be used as attributes:
+ *  - cv::String
+ *  - int
+ *  - double
+ *  - cv::InputArray (n-d continuous multichannel arrays)
+ *
+ * Although HDF supports associating attributes with both datasets and groups,
+ * only support for the root group is implemented by OpenCV at present.
+ */
+
+//! [tutorial]
+#include <iostream>
+
+#include <opencv2/core.hpp>
+#include <opencv2/hdf.hpp>
+
+using namespace cv;
+
+static void read_write_attributes()
+{
+    String filename = "attributes.h5";
+
+    //! [tutorial_open_file]
+    Ptr<hdf::HDF5> h5io = hdf::open(filename);
+    //! [tutorial_open_file]
+
+    //! [tutorial_write_mat]
+    String attr_mat_name = "array attribute";
+    Mat attr_mat;
+    attr_mat = (cv::Mat_<float>(2, 3) << 0, 1, 2, 3, 4, 5, 6);
+    if (!h5io->atexists(attr_mat_name))
+        h5io->atwrite(attr_mat, attr_mat_name);
+    //! [tutorial_write_mat]
+
+    //! [snippets_write_str]
+    String attr_str_name = "string attribute";
+    String attr_str = "Hello HDF5 from OpenCV!";
+    if (!h5io->atexists(attr_str_name))
+        h5io->atwrite(attr_str, attr_str_name);
+    //! [snippets_write_str]
+
+    String attr_int_name = "int attribute";
+    int attr_int = 123456;
+    if (!h5io->atexists(attr_int_name))
+        h5io->atwrite(attr_int, attr_int_name);
+
+    String attr_double_name = "double attribute";
+    double attr_double = 45678.123;
+    if (!h5io->atexists(attr_double_name))
+        h5io->atwrite(attr_double, attr_double_name);
+
+    // read attributes
+    Mat expected_attr_mat;
+    int expected_attr_int;
+    double expected_attr_double;
+
+    //! [snippets_read_str]
+    String expected_attr_str;
+    h5io->atread(&expected_attr_str, attr_str_name);
+    //! [snippets_read_str]
+
+    //! [tutorial_read_mat]
+    h5io->atread(expected_attr_mat, attr_mat_name);
+    //! [tutorial_read_mat]
+    h5io->atread(&expected_attr_int, attr_int_name);
+    h5io->atread(&expected_attr_double, attr_double_name);
+
+    // check results
+    CV_Assert(norm(attr_mat - expected_attr_mat) < 1e-10);
+    CV_Assert(attr_str.compare(expected_attr_str) == 0);
+    CV_Assert(attr_int == expected_attr_int);
+    CV_Assert(fabs(attr_double - expected_attr_double) < 1e-10);
+
+    //! [tutorial_close_file]
+    h5io->close();
+    //! [tutorial_close_file]
+}
+
+int main()
+{
+    read_write_attributes();
+
+    return 0;
+}
+//! [tutorial]