Merge pull request #1500 from csukuangfj:hdf-attributes-support
Alexander Alekhin
7 years ago
commit
31bd7d986a
12 changed files with 654 additions and 40 deletions
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/**
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* @file read_write_attributes.cpp |
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* @author Fangjun Kuang <csukuangfj dot at gmail dot com> |
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* @date December 2017 |
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* |
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* @brief It demonstrates how to read and write attributes inside the |
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* root group. |
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* |
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* Currently, only the following datatypes can be used as attributes: |
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* - cv::String |
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* - int |
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* - double |
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* - cv::InputArray (n-d continuous multichannel arrays) |
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* |
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* Although HDF supports associating attributes with both datasets and groups, |
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* only support for the root group is implemented by OpenCV at present. |
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*/ |
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//! [tutorial]
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#include <iostream> |
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#include <opencv2/core.hpp> |
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#include <opencv2/hdf.hpp> |
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using namespace cv; |
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static void read_write_attributes() |
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{ |
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String filename = "attributes.h5"; |
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//! [tutorial_open_file]
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Ptr<hdf::HDF5> h5io = hdf::open(filename); |
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//! [tutorial_open_file]
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//! [tutorial_write_mat]
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String attr_mat_name = "array attribute"; |
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Mat attr_mat; |
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attr_mat = (cv::Mat_<float>(2, 3) << 0, 1, 2, 3, 4, 5, 6); |
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if (!h5io->atexists(attr_mat_name)) |
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h5io->atwrite(attr_mat, attr_mat_name); |
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//! [tutorial_write_mat]
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//! [snippets_write_str]
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String attr_str_name = "string attribute"; |
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String attr_str = "Hello HDF5 from OpenCV!"; |
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if (!h5io->atexists(attr_str_name)) |
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h5io->atwrite(attr_str, attr_str_name); |
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//! [snippets_write_str]
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String attr_int_name = "int attribute"; |
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int attr_int = 123456; |
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if (!h5io->atexists(attr_int_name)) |
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h5io->atwrite(attr_int, attr_int_name); |
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String attr_double_name = "double attribute"; |
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double attr_double = 45678.123; |
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if (!h5io->atexists(attr_double_name)) |
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h5io->atwrite(attr_double, attr_double_name); |
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// read attributes
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Mat expected_attr_mat; |
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int expected_attr_int; |
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double expected_attr_double; |
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//! [snippets_read_str]
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String expected_attr_str; |
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h5io->atread(&expected_attr_str, attr_str_name); |
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//! [snippets_read_str]
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//! [tutorial_read_mat]
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h5io->atread(expected_attr_mat, attr_mat_name); |
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//! [tutorial_read_mat]
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h5io->atread(&expected_attr_int, attr_int_name); |
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h5io->atread(&expected_attr_double, attr_double_name); |
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// check results
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CV_Assert(norm(attr_mat - expected_attr_mat) < 1e-10); |
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CV_Assert(attr_str.compare(expected_attr_str) == 0); |
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CV_Assert(attr_int == expected_attr_int); |
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CV_Assert(fabs(attr_double - expected_attr_double) < 1e-10); |
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//! [tutorial_close_file]
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h5io->close(); |
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//! [tutorial_close_file]
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} |
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int main() |
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{ |
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read_write_attributes(); |
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return 0; |
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} |
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//! [tutorial]
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Reading and Writing Attributes{#tutorial_hdf_read_write_attributes} |
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=============================== |
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Goal |
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---- |
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This tutorial shows you: |
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- How to write attributes? |
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- How to read attributes? |
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@note Although attributes can be associated with groups and datasets, only attributes |
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with the root group are implemented in OpenCV. Supported attribute types are |
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`int`, `double`, `cv::String` and `cv::InputArray` (only for continuous arrays). |
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Source Code |
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---- |
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The following code demonstrates reading and writing attributes |
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inside the root group with data types `cv::Mat`, `cv::String`, `int` |
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and `double`. |
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You can download the code from [here][1] or find it in the file |
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`modules/hdf/samples/read_write_attributes.cpp` of the opencv_contrib source code library. |
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@snippet samples/read_write_attributes.cpp tutorial |
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Explanation |
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---- |
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The first step is to open the HDF5 file: |
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@snippet samples/read_write_attributes.cpp tutorial_open_file |
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Then we use cv::hdf::HDF5::atwrite() to write attributes by specifying its value and name: |
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@snippet samples/read_write_attributes.cpp tutorial_write_mat |
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@warning Before writing an attribute, we have to make sure that |
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the attribute does not exist using cv::hdf::HDF5::atexists(). |
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To read an attribute, we use cv::hdf::HDF5::atread() by specifying the attribute name |
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@snippet samples/read_write_attributes.cpp tutorial_read_mat |
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In the end, we have to close the HDF file |
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@snippet samples/read_write_attributes.cpp tutorial_close_file |
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Results |
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---- |
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Figure 1 and Figure 2 give the results visualized using the tool HDFView. |
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 |
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 |
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[1]: https://github.com/opencv/opencv_contrib/tree/master/modules/hdf/samples/read_write_attributes.cpp |
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