discrete_fourier_transform

Shows the magnitude spectrum of the discrete Fourier transform (cv::dft()) of the image.

opencv_apps	1.11.15 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`

Usage

# ROS 2
ros2 launch opencv_apps discrete_fourier_transform.launch.xml image:=/camera/image_raw debug_view:=false
# ROS 1
roslaunch opencv_apps discrete_fourier_transform.launch image:=/camera/image_raw 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:

wget https://ros-perception.github.io/opencv_apps/media/clips/street.mp4
# terminal 1: publish the video as image in a loop
ros2 run image_publisher image_publisher_node street.mp4 --ros-args -p publish_rate:=10.0 -r image_raw:=image
# terminal 2: run the node
ros2 launch opencv_apps discrete_fourier_transform.launch.xml image:=image
# terminal 3: view the result
ros2 run rqt_image_view rqt_image_view /discrete_fourier_transform/image

In ROS 1:

# terminal 1
rosrun image_publisher image_publisher street.mp4 _publish_rate:=10 __name:=camera
# terminal 2
roslaunch opencv_apps discrete_fourier_transform.launch image:=camera/image_raw

See Credits of the demo videos for the license of the video.

Subscribed topics

Topic	Type
`image`	`sensor_msgs/msg/Image`

Published topics

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

Parameters

Source

src/nodelet/discrete_fourier_transform_nodelet.cpp, launch/discrete_fourier_transform.launch.xml