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Reading and Writing Attributes{#tutorial_hdf_read_write_attributes}
===============================
Goal
----
This tutorial shows you:
- How to write attributes?
- How to read attributes?
@note Although attributes can be associated with groups and datasets, only attributes
with the root group are implemented in OpenCV. Supported attribute types are
`int`, `double`, `cv::String` and `cv::InputArray` (only for continuous arrays).
Source Code
----
The following code demonstrates reading and writing attributes
inside the root group with data types `cv::Mat`, `cv::String`, `int`
and `double`.
You can download the code from [here][1] or find it in the file
`modules/hdf/samples/read_write_attributes.cpp` of the opencv_contrib source code library.
@snippet samples/read_write_attributes.cpp tutorial
Explanation
----
The first step is to open the HDF5 file:
@snippet samples/read_write_attributes.cpp tutorial_open_file
Then we use cv::hdf::HDF5::atwrite() to write attributes by specifying its value and name:
@snippet samples/read_write_attributes.cpp tutorial_write_mat
@warning Before writing an attribute, we have to make sure that
the attribute does not exist using cv::hdf::HDF5::atexists().
To read an attribute, we use cv::hdf::HDF5::atread() by specifying the attribute name
@snippet samples/read_write_attributes.cpp tutorial_read_mat
In the end, we have to close the HDF file
@snippet samples/read_write_attributes.cpp tutorial_close_file
Results
----
Figure 1 and Figure 2 give the results visualized using the tool HDFView.
[1]: https://github.com/opencv/opencv_contrib/tree/master/modules/hdf/samples/read_write_attributes.cpp
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