init - 初始化项目

doc/tutorials/introduction/display_image/display_image.markdown

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+Getting Started with Images {#tutorial_display_image}
+===========================
+
+@prev_tutorial{tutorial_building_tegra_cuda}
+@next_tutorial{tutorial_documentation}
+
+|    |    |
+| -: | :- |
+| Original author | Ana Huamán |
+| Compatibility | OpenCV >= 3.4.4 |
+
+@warning
+This tutorial can contain obsolete information.
+
+Goal
+----
+
+In this tutorial you will learn how to:
+
+-   Read an image from file (using @ref cv::imread)
+-   Display an image in an OpenCV window (using @ref cv::imshow)
+-   Write an image to a file (using @ref cv::imwrite)
+
+Source Code
+-----------
+
+@add_toggle_cpp
+-   **Downloadable code**: Click
+    [here](https://github.com/opencv/opencv/tree/master/samples/cpp/tutorial_code/introduction/display_image/display_image.cpp)
+
+-   **Code at glance:**
+    @include samples/cpp/tutorial_code/introduction/display_image/display_image.cpp
+@end_toggle
+
+@add_toggle_python
+-   **Downloadable code**: Click
+    [here](https://github.com/opencv/opencv/tree/master/samples/python/tutorial_code/introduction/display_image/display_image.py)
+
+-   **Code at glance:**
+    @include samples/python/tutorial_code/introduction/display_image/display_image.py
+@end_toggle
+
+
+Explanation
+-----------
+
+@add_toggle_cpp
+In OpenCV 3 we have multiple modules. Each one takes care of a different area or approach towards
+image processing. You could already observe this in the structure of the user guide of these
+tutorials itself. Before you use any of them you first need to include the header files where the
+content of each individual module is declared.
+
+You'll almost always end up using the:
+
+- @ref core "core" section, as here are defined the basic building blocks of the library
+- @ref imgcodecs "imgcodecs" module, which provides functions for reading and writing
+- @ref highgui "highgui" module, as this contains the functions to show an image in a window
+
+We also include the *iostream* to facilitate console line output and input.
+
+By declaring `using namespace cv;`, in the following, the library functions can be accessed without explicitly stating the namespace.
+
+@snippet cpp/tutorial_code/introduction/display_image/display_image.cpp includes
+@end_toggle
+
+@add_toggle_python
+As a first step, the OpenCV python library is imported.
+The proper way to do this is to additionally assign it the name *cv*, which is used in the following to reference the library.
+
+@snippet samples/python/tutorial_code/introduction/display_image/display_image.py imports
+@end_toggle
+
+Now, let's analyze the main code.
+As a first step, we read the image "starry_night.jpg" from the OpenCV samples.
+In order to do so, a call to the @ref cv::imread function loads the image using the file path specified by the first argument.
+The second argument is optional and specifies the format in which we want the image. This may be:
+
+-   IMREAD_COLOR loads the image in the BGR 8-bit format. This is the **default** that is used here.
+-   IMREAD_UNCHANGED loads the image as is (including the alpha channel if present)
+-   IMREAD_GRAYSCALE loads the image as an intensity one
+
+After reading in the image data will be stored in a @ref cv::Mat object.
+
+@add_toggle_cpp
+@snippet cpp/tutorial_code/introduction/display_image/display_image.cpp imread
+@end_toggle
+
+@add_toggle_python
+@snippet samples/python/tutorial_code/introduction/display_image/display_image.py imread
+@end_toggle
+
+@note
+   OpenCV offers support for the image formats Windows bitmap (bmp), portable image formats (pbm,
+    pgm, ppm) and Sun raster (sr, ras). With help of plugins (you need to specify to use them if you
+    build yourself the library, nevertheless in the packages we ship present by default) you may
+    also load image formats like JPEG (jpeg, jpg, jpe), JPEG 2000 (jp2 - codenamed in the CMake as
+    Jasper), TIFF files (tiff, tif) and portable network graphics (png). Furthermore, OpenEXR is
+    also a possibility.
+
+Afterwards, a check is executed, if the image was loaded correctly.
+@add_toggle_cpp
+@snippet cpp/tutorial_code/introduction/display_image/display_image.cpp empty
+@end_toggle
+
+@add_toggle_python
+@snippet samples/python/tutorial_code/introduction/display_image/display_image.py empty
+@end_toggle
+
+Then, the image is shown using a call to the @ref cv::imshow function.
+The first argument is the title of the window and the second argument is the @ref cv::Mat object that will be shown.
+
+Because we want our window to be displayed until the user presses a key (otherwise the program would
+end far too quickly), we use the @ref cv::waitKey function whose only parameter is just how long
+should it wait for a user input (measured in milliseconds). Zero means to wait forever.
+The return value is the key that was pressed.
+
+@add_toggle_cpp
+@snippet cpp/tutorial_code/introduction/display_image/display_image.cpp imshow
+@end_toggle
+
+@add_toggle_python
+@snippet samples/python/tutorial_code/introduction/display_image/display_image.py imshow
+@end_toggle
+
+In the end, the image is written to a file if the pressed key was the "s"-key.
+For this the cv::imwrite function is called that has the file path and the cv::Mat object as an argument.
+
+@add_toggle_cpp
+@snippet cpp/tutorial_code/introduction/display_image/display_image.cpp imsave
+@end_toggle
+
+@add_toggle_python
+@snippet samples/python/tutorial_code/introduction/display_image/display_image.py imsave
+@end_toggle