adding_images
=============

Blends two images, ``image1`` and ``image2``, with ``cv::addWeighted()``: alpha * image1 + beta * image2 + gamma. The two images are synchronized by their time stamps.

.. list-table::
   :stub-columns: 1

   * - opencv_apps
     - 1.11.14 and later (ROS 1), 3.0.0 and later (ROS 2)
   * - ROS
     - noetic, ROS One, jazzy, kilted, lyrical and later
   * - OpenCV
     - any version of the distributions
   * - Group
     - Image filters, the nodes of which publish the processed image in ``~/image``

.. image:: https://ros-perception.github.io/opencv_apps/media/adding_images.gif
   :alt: demo of adding_images

Usage
-----

.. code-block:: bash

   # ROS 2
   ros2 launch opencv_apps adding_images.launch.xml image1:=/camera/image_raw image2:=/camera2/image_raw approximate_sync:=true debug_view:=false
   # ROS 1
   roslaunch opencv_apps adding_images.launch image1:=/camera/image_raw image2:=/camera2/image_raw approximate_sync:=true debug_view:=false

Try it with the demo video
--------------------------

Download the input video of the demo above, publish it as ``image`` with ``image_publisher``, and run the node on it, in the terminals:

.. code-block:: bash

   wget https://ros-perception.github.io/opencv_apps/media/clips/tos_bridge.mp4
   wget https://ros-perception.github.io/opencv_apps/media/clips/pool.mp4  # image2
   # terminal 1: publish the video as image in a loop
   ros2 run image_publisher image_publisher_node tos_bridge.mp4 --ros-args -p publish_rate:=10.0 -r image_raw:=image
   # terminal 2: run the node with the parameters of the demo
   ros2 launch opencv_apps adding_images.launch.xml image1:=image image2:=image2 alpha:=0.5 approximate_sync:=true gamma:=0.0
   # terminal 3: run, keep it running
   ros2 run image_publisher image_publisher_node pool.mp4 --ros-args -p publish_rate:=10.0 -r image_raw:=image2 -r camera_info:=camera_info2
   # terminal 4: view the result
   ros2 run rqt_image_view rqt_image_view /adding_images/image

image1 is tos_bridge.mp4 and image2 is pool.mp4, both 960x540.

See :doc:`../credits` for the license of the video.

Subscribed topics
-----------------

.. list-table::
   :header-rows: 1

   * - Topic
     - Type
   * - ``camera_info``
     - ``sensor_msgs/msg/CameraInfo``
   * - ``image1``
     - ``sensor_msgs/msg/Image``
   * - ``image2``
     - ``sensor_msgs/msg/Image``

Published topics
----------------

.. list-table::
   :header-rows: 1

   * - Topic
     - Type
   * - ``~/image``
     - ``sensor_msgs/msg/Image``

Parameters
----------

See also the :ref:`common parameters <common-parameters>`.

.. list-table::
   :header-rows: 1

   * - Name
     - Type
     - Default (range)
     - Changed at run time
     - Description
   * - ``alpha``
     - double
     - 0.5 (0 - 1)
     - yes
     - weight of the first array elements.
   * - ``approximate_sync``
     - bool
     - true
     - no, restart the node
     - Flag of approximate_sync. If this value is false, image1 and image2 synchronize exact time.
   * - ``auto_beta``
     - bool
     - true
     - yes
     - True: Automatically set beta weight as 1 - alpha, False: Use user defined beta weight
   * - ``beta``
     - double
     - 0.5 (0 - 1)
     - yes
     - weight of the second array elements.
   * - ``gamma``
     - double
     - 0.0 (0 - 255)
     - yes
     - scalar added to each sum.
   * - ``queue_size``
     - int
     - 100
     - no, restart the node
     - Specigy queue_size of input image subscribers

Source
------

`src/nodelet/adding_images_nodelet.cpp <https://github.com/ros-perception/opencv_apps/blob/indigo/src/nodelet/adding_images_nodelet.cpp>`_, 
`launch/adding_images.launch.xml <https://github.com/ros-perception/opencv_apps/blob/indigo/launch/adding_images.launch.xml>`_