vendor: OpenCV 5.0.0 snapshot at 755e50675d97db9b7d449d8bd6b09888646f6c6e

modules/hdf/samples/create_groups.cpp

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+/**
+ * @file create_groups.cpp
+ * @author Fangjun Kuang <csukuangfj dot at gmail dot com>
+ * @date December 2017
+ *
+ * @brief It demonstrates how to create HDF5 groups and subgroups.
+ *
+ * Basic steps:
+ *  1. Use hdf::open to create a HDF5 file
+ *  2. Use HDF5::hlexists to check if a group exists or not
+ *  3. Use HDF5::grcreate to create a group by specifying its name
+ *  4. Use hdf::close to close a HDF5 file after modifying it
+ *
+ */
+
+//! [tutorial]
+#include <iostream>
+
+#include <opencv2/core.hpp>
+#include <opencv2/hdf.hpp>
+
+using namespace cv;
+
+int main()
+{
+    //! [create_group]
+
+    //! [tutorial_create_file]
+    Ptr<hdf::HDF5> h5io = hdf::open("mytest.h5");
+    //! [tutorial_create_file]
+
+    //! [tutorial_create_group]
+    // "/" means the root group, which is always present
+    if (!h5io->hlexists("/Group1"))
+       h5io->grcreate("/Group1");
+    else
+       std::cout << "/Group1 has already been created, skip it.\n";
+    //! [tutorial_create_group]
+
+    //! [tutorial_create_subgroup]
+    // Note that Group1 has been created above, otherwise exception will occur
+    if (!h5io->hlexists("/Group1/SubGroup1"))
+       h5io->grcreate("/Group1/SubGroup1");
+    else
+       std::cout << "/Group1/SubGroup1 has already been created, skip it.\n";
+    //! [tutorial_create_subgroup]
+
+    //! [tutorial_close_file]
+    h5io->close();
+    //! [tutorial_close_file]
+
+    //! [create_group]
+
+    return 0;
+}
+//! [tutorial]

modules/hdf/samples/create_read_write_datasets.cpp

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+/**
+ * @file create_read_write_datasets.cpp
+ * @author Fangjun Kuang <csukuangfj dot at gmail dot com>
+ * @date December 2017
+ *
+ * @brief It demonstrates how to create a dataset,  how
+ * to write a cv::Mat to the dataset and how to
+ * read a cv::Mat from it.
+ *
+ */
+
+//! [tutorial]
+#include <iostream>
+
+#include <opencv2/core.hpp>
+#include <opencv2/hdf.hpp>
+
+using namespace cv;
+
+static void write_root_group_single_channel()
+{
+    String filename = "root_group_single_channel.h5";
+    String dataset_name = "/single"; // Note that it is a child of the root group /
+
+    // prepare data
+    Mat data;
+    data = (cv::Mat_<float>(2, 3) << 0, 1, 2, 3, 4, 5, 6);
+
+    //! [tutorial_open_file]
+    Ptr<hdf::HDF5> h5io = hdf::open(filename);
+    //! [tutorial_open_file]
+
+    //! [tutorial_write_root_single_channel]
+    // write data to the given dataset
+    // the dataset "/single" is created automatically, since it is a child of the root
+    h5io->dswrite(data, dataset_name);
+    //! [tutorial_write_root_single_channel]
+
+    //! [tutorial_read_dataset]
+    Mat expected;
+    h5io->dsread(expected, dataset_name);
+    //! [tutorial_read_dataset]
+
+    //! [tutorial_check_result]
+    double diff = norm(data - expected);
+    CV_Assert(abs(diff) < 1e-10);
+    //! [tutorial_check_result]
+
+    h5io->close();
+}
+
+static void write_single_channel()
+{
+    String filename = "single_channel.h5";
+    String parent_name = "/data";
+    String dataset_name = parent_name + "/single";
+
+    // prepare data
+    Mat data;
+    data = (cv::Mat_<float>(2, 3) << 0, 1, 2, 3, 4, 5);
+
+    Ptr<hdf::HDF5> h5io = hdf::open(filename);
+
+    //! [tutorial_create_dataset]
+    // first we need to create the parent group
+    if (!h5io->hlexists(parent_name)) h5io->grcreate(parent_name);
+
+    // create the dataset if it not exists
+    if (!h5io->hlexists(dataset_name)) h5io->dscreate(data.rows, data.cols, data.type(), dataset_name);
+    //! [tutorial_create_dataset]
+
+    // the following is the same with the above function write_root_group_single_channel()
+
+    h5io->dswrite(data, dataset_name);
+
+    Mat expected;
+    h5io->dsread(expected, dataset_name);
+
+    double diff = norm(data - expected);
+    CV_Assert(abs(diff) < 1e-10);
+
+    h5io->close();
+}
+
+/*
+ * creating, reading and writing multiple-channel matrices
+ * are the same with single channel matrices
+ */
+static void write_multiple_channels()
+{
+    String filename = "two_channels.h5";
+    String parent_name = "/data";
+    String dataset_name = parent_name + "/two_channels";
+
+    // prepare data
+    Mat data(2, 3, CV_32SC2);
+    for (size_t i = 0; i < data.total()*data.channels(); i++)
+        ((int*) data.data)[i] = (int)i;
+
+    Ptr<hdf::HDF5> h5io = hdf::open(filename);
+
+    // first we need to create the parent group
+    if (!h5io->hlexists(parent_name)) h5io->grcreate(parent_name);
+
+    // create the dataset if it not exists
+    if (!h5io->hlexists(dataset_name)) h5io->dscreate(data.rows, data.cols, data.type(), dataset_name);
+
+    // the following is the same with the above function write_root_group_single_channel()
+
+    h5io->dswrite(data, dataset_name);
+
+    Mat expected;
+    h5io->dsread(expected, dataset_name);
+
+    double diff = norm(data - expected);
+    CV_Assert(abs(diff) < 1e-10);
+
+    h5io->close();
+}
+
+int main()
+{
+    write_root_group_single_channel();
+
+    write_single_channel();
+
+    write_multiple_channels();
+
+    return 0;
+}
+//! [tutorial]

modules/hdf/samples/read_write_attributes.cpp

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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]