cv_undistort_image module

Undistortion a fisheyelens distortion of a whole image

Note that this is quite a slow process, so it is not really advisable to use this in a vision pipeline leading to control. However, it can be used to find the right undistortion parameter k, and shows that the undistortion functions work.

The code also can be used to convert image coordinates from distorted fisheye lenses to undistorted coordinates and back. It takes into account the camera calibration matrix and the distortion of the specific lens.

Example for airframe file

Add to your firmware section: This example contains all possible configuration options, not all of them are mandatory!

<module name="video_thread"/>
<module name="cv_undistort_image">
  <define name="UNDISTORT_MIN_X_NORMALIZED" value="-2.0" />
  <define name="UNDISTORT_MAX_X_NORMALIZED" value="2.0" />
  <define name="UNDISTORT_FPS" value="0" />
  <define name="UNDISTORT_CAMERA" value="bottom_camera|front_camera" />
  <define name="UNDISTORT_CENTER_RATIO" value="1.0" />
</module>

Module configuration options

Define Options

• name: UNDISTORT_MIN_X_NORMALIZED value: -2.0
  Description: Minimal normalized x-coordinate to be used for the undistortion
• name: UNDISTORT_MAX_X_NORMALIZED value: 2.0
  Description: Maximal normalized x-coordinate to be used for the undistortion
• name: UNDISTORT_FPS value: 0
  Description: The (maximum) frequency to run the calculations at. If zero, it will max out at the camera frame rate
• name: UNDISTORT_CAMERA value: bottom_camera|front_camera
  Description: The V4L2 camera device that is used for the calculations
• name: UNDISTORT_CENTER_RATIO value: 1.0
  Description: If smaller than 1 only generate pixels for the center_ratio times the min_x to max_x interval. This makes undistortion quicker, but for a smaller FOV.

Dependencies

• video_thread module

Module functions

Init Functions

These initialization functions are called once on startup.

• undistort_image_init()

Files

Header Files

The following headers are automatically included in modules.h

• undistort_image.h

Source Files

• modules/computer_vision/undistort_image.c
• modules/computer_vision/lib/vision/image.c
• modules/computer_vision/lib/vision/undistortion.c

Raw cv_undistort_image.xml file:

<!DOCTYPE module SYSTEM "module.dtd">

<module name="cv_undistort_image" dir="computer_vision">
  <doc>
    <description>
      Undistortion a fisheyelens distortion of a whole image. 
      Note that this is quite a slow process, so it is not really advisable to use this in a vision pipeline leading to control. 
      However, it can be used to find the right undistortion parameter k, and shows that the undistortion functions work.

      The code also can be used to convert image coordinates from distorted fisheye lenses to undistorted coordinates and back.
      It takes into account the camera calibration matrix and the distortion of the specific lens.
    </description>
    <define name="UNDISTORT_MIN_X_NORMALIZED" value="-2.0" description="Minimal normalized x-coordinate to be used for the undistortion"/>
    <define name="UNDISTORT_MAX_X_NORMALIZED" value="2.0" description="Maximal normalized x-coordinate to be used for the undistortion"/>
    <define name="UNDISTORT_FPS" value="0" description="The (maximum) frequency to run the calculations at. If zero, it will max out at the camera frame rate"/>
    <define name="UNDISTORT_CAMERA" value="bottom_camera|front_camera" description="The V4L2 camera device that is used for the calculations"/>
    <define name="UNDISTORT_CENTER_RATIO" value="1.0" description="If smaller than 1 only generate pixels for the center_ratio times the min_x to max_x interval. This makes undistortion quicker, but for a smaller FOV."/>
  </doc>

  <settings>
    <dl_settings>
      <dl_settings NAME="Undistort">
  <dl_setting var="min_x_normalized"  min="-4.0" step="0.1" max="0.0" shortname="min_x_n" param="UNDISTORT_MIN_X_NORMALIZED"/>
  <dl_setting var="max_x_normalized"  min="0.1" step="0.1" max="4.0" shortname="max_x_n" param="UNDISTORT_MAX_X_NORMALIZED"/>
  <dl_setting var="camera_intrinsics.Dhane_k"  min="1.0" step="0.01" max="2.5" shortname="dhane_k" param="UNDISTORT_DHANE_K"/>
  <dl_setting var="center_ratio"  min="0.05" step="0.01" max="1.0" shortname="center_ratio" param="UNDISTORT_CENTER_RATIO"/>
  <dl_setting var="camera_intrinsics.focal_x"  min="0.0" step="0.05" max="1024.0" shortname="focal_x" param="UNDISTORT_FOCAL_X"/>
  <dl_setting var="camera_intrinsics.center_x"  min="0.0" step="0.05" max="1024.0" shortname="center_x" param="UNDISTORT_CENTER_X"/>
  <dl_setting var="camera_intrinsics.focal_y"  min="0.0" step="0.05" max="1024.0" shortname="focal_y" param="UNDISTORT_FOCAL_Y"/>
  <dl_setting var="camera_intrinsics.center_y"  min="0.0" step="0.05" max="1024.0" shortname="center_y" param="UNDISTORT_CENTER_Y"/>
      </dl_settings>
    </dl_settings>
  </settings>

  <depends>video_thread</depends>

  <header>
    <file name="undistort_image.h"/>
  </header>

  <init fun="undistort_image_init()"/>
  <makefile target="ap|nps">
    <file name="undistort_image.c"/>
    <file name="image.c" dir="modules/computer_vision/lib/vision"/>
    <file name="undistortion.c" dir="modules/computer_vision/lib/vision"/>    
  </makefile>
</module>