This module isolates pixels within a given HSV range (hue, saturation, and value of color pixels), does some cleanups, and extracts object contours. It is looking for a rectangular U shape of a specific size (set by parameter
This module usually works best with the camera sensor set to manual exposure, manual gain, manual color balance, etc so that HSV color values are reliable. See the file script.cfg file in this module's directory for an example of how to set the camera settings each time this module is loaded.
This module is provided for inspiration. It has no pretension of actually solving the FIRST Robotics vision problem in a complete and reliable way. It is released in the hope that FRC teams will try it out and get inspired to develop something much better for their own robot.
The basic idea of this module is the classic FIRST robotics vision pipeline: first, select a range of pixels in HSV color pixel space likely to include the object. Then, detect contours of all blobs in range. Then apply some tests on the shape of the detected blobs, their size, fill ratio (ratio of object area compared to its convex hull's area), etc. Finally, estimate the location and pose of the object in the world.
In this module, we run up to 4 pipelines in parallel, using different settings for the range of HSV pixels considered:
Detections from all 4 pipelines are considered for overlap and quality (raggedness of their outlines), and only the cleanest of several overlapping detections is preserved. From those cleanest detections, pipelines 2-3 learn and adapt the HSV range for future video frames.
Using this module
Check out this tutorial.
Detection and quality control steps
The following messages appear for each of the 4 pipelines, at the bottom of the demo video, to help users figure out why their object may not be detected:
The black and white picture at right shows the pixels in HSV range for the thread determined by parameter
This module can send standardized serial messages as described in Standardized serial messages formatting. One message is issued on every video frame for each detected and good object. The
2D messages when
3D messages when
NOTE: 3D pose estimation from low-resolution 176x144 images at 120fps can be quite noisy. Make sure you tune your HSV ranges very well if you want to operate at 120fps (see below). To operate more reliably at very low resolutions, one may want to improve this module by adding subpixel shape refinement and tracking across frames.
See Standardized serial messages formatting for more on standardized serial messages, and Helper functions to convert coordinates from camera resolution to standardized for more info on standardized coordinates.
Trying it out
The default parameter settings (which are set in script.cfg explained below) attempt to detect yellow-green objects. Present an object to the JeVois camera and see whether it is detected. When detected and good enough according to a number of quality control tests, the outline of the object is drawn.
For further use of this module, you may want to check out the following tutorials:
You need to provide the exact width and height of your physical shape to parameter
You should adjust parameters
Tuning the parameters is best done interactively by connecting to your JeVois camera while it is looking at some object of the desired color. Once you have achieved a tuning, you may want to set the hcue, scue, and vcue parameters in your script.cfg file for this module on the microSD card (see below).
Typically, you would start by narrowing down on the hue, then the value, and finally the saturation. Make sure you also move your camera around and show it typical background clutter so check for false positives (detections of things which you are not interested, which can happen if your ranges are too wide).
JeVois allows you to store parameter settings and commands in a file named script.cfg stored in the directory of a module. The file script.cfg may contain any sequence of commands as you would type them interactively in the JeVois command-line interface. For the FirstVision module, a default script is provided that sets the camera to manual color, gain, and exposure mode (for more reliable color values), and other example parameter values.
The script.cfg file for FirstVision is stored on your microSD at JEVOIS:/modules/JeVois/FirstVision/script.cfg