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Visual Servoing Platform
version 3.5.0 under development (2022-02-15)
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Visual Servoing Platform
version 3.5.0 under development (2022-02-15)
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In this tutorial you will learn how to grab images with ViSP, either from cameras or from a video stream.
Grabbing images from a real camera is only possible if you have installed the corresponding 3rd party. The complete list of 3rd parties supported by ViSP and dedicated to framegrabbing is given here. From this page you will also found useful information to install these 3rd parties.
All the material (source code and videos) described in this tutorial is part of ViSP source code and could be downloaded using the following command:
$ svn export https://github.com/lagadic/visp.git/trunk/tutorial/grabber
After ViSP 3.0.0, we introduce vpFlyCaptureGrabber class, a wrapper over PointGrey FlyCapture SDK that allows to grab images from any PointGrey camera. This grabber was tested under Ubuntu and Windows with the following cameras:
It should also work with GigE PGR cameras.
The following example also available in tutorial-grabber-flycapture.cpp shows how to use vpFlyCaptureGrabber to capture grey level images from a PointGrey camera under Ubuntu or Windows. The following example suppose that a window renderer (libX11 on Ubuntu or GDI on Windows) and FlyCapture SDK 3rd party are available throw VISP.
Here after we explain the source code.
First an instance of the frame grabber is created.
Once the grabber is created, we turn auto shutter and auto gain on and set the camera image size, color coding, and framerate. These settings are enclosed in a try/catch to be able to continue if one of these settings are not supported by the camera.
Then the grabber is initialized using:
From now the grey level image I is also initialized with the size corresponding to the grabber settings.
Then we enter in a while loop where image acquisition is simply done by:
This image is then displayed using libX11 or GDI renderer:
Depending on the command line options we are recording a sequence of images, or single shot images. We are also waiting for a non blocking mouse event to quit the while loop.
Once tutorial-grabber-flycapture.cpp is built, the binary usage is given by:
To just view images, run:
To grab single shot images (for camera calibration for example), you may use:
To grab a sequence of images, you may rather use:
The next example also available in tutorial-grabber-1394.cpp shows how to use a framegrabber to acquire color images from a firewire or USB3 camera under Unix. The following example suppose that libX11 and libdc1394-2 3rd party are available.
The source code is the following:
Here after we explain the new lines that are introduced.
First an instance of the frame grabber is created. During the creating a bus reset is send. If you don't want to reset the firewire bus, just turn reset to false.
Once the grabber is created, we set the camera image size, color coding, and framerate.
Note that here you can specify some other settings such as the firewire transmission speed. For a more complete list of settings see vp1394TwoGrabber class.
Then the grabber is initialized using:
From now the color image I is also initialized with the size corresponding to the grabber settings.
Then we enter in a while loop where image acquisition is simply done by:
As in the previous example, depending on the command line options we are recording a sequence of images, or single shot images. We are also waiting for a non blocking mouse event to quit the while loop.
In the previous example we use vp1394TwoGrabber class that works for firewire cameras under Unix. If you are under Windows, you may use vp1394CMUGrabber class. A similar example is provided in tutorial-grabber-CMU1394.cpp.
Once tutorial-grabber-1394.cpp is built, the binary usage is given by:
To just view images, run:
To grab single shot images (for camera calibration for example), you may use:
To grab a sequence of images, you may rather use:
If you want to grab images from an usb camera under Unix, you may use vpV4l2Grabber class that is a wrapper over Video For Linux SDK. To this end libv4l should be installed. An example is provided in tutorial-grabber-v4l2.cpp.
Once tutorial-grabber-v4l2.cpp is built, the binary usage is given by:
To just view images, run:
To grab single shot images (for camera calibration for example), you may use:
To grab a sequence of images, you may rather use:
It is also possible to grab images using Pylon, the SDK for Basler cameras. You may find an example in tutorial-grabber-basler-pylon.cpp.
Once tutorial-grabber-basler-pylon.cpp is built, the binary usage is given by:
To just view images, run:
To grab single shot images (for camera calibration for example), you may use:
To grab a sequence of images, you may rather use:
It is also possible to grab images using librealsense, the SDK provided for Intel Realsense RDB-D cameras. You may find an example in tutorial-grabber-realsense.cpp.
Once tutorial-grabber-realsense.cpp is built, the binary usage is given by:
To just view images, run:
To grab single shot images (for camera calibration for example), you may use:
To grab a sequence of images, you may rather use:
Once tutorial-grabber-multiple-realsense.cpp is built, the binary usage is given by:
To acquire images from 2 T265 devices with serial numbers 11622110511 and 11622110433 respectively, run:
To acquire images from 1 T265 device (Serial Number:11622110511) and 1 D435 device (Serial Number: 752112070408), you may use:
example/device/framegrabber folder that could be used to get the device serial number. $ ./getRealSense2Info
RealSense characteristics:
Intel RealSense T265 11622110409 0.2.0.951
Device info:
Name : Intel RealSense T265
Serial Number : 11622110409
Firmware Version : 0.2.0.951
Physical Port : 2-3-2
Product Id : 0B37
Usb Type Descriptor : 3.1
Product Line : T200
If you have a Structure Core RGB-D camera, it is also possible to grab images using libStructure the cross-platform library that comes with Occipital Structure SDK. You may find an example in tutorial-grabber-structure-core.cpp. It allows to save visible and depth images.
Once tutorial-grabber-structure-core.cpp is built, the binary usage is given by:
To just view images, run:
To grab single shot images (for camera calibration for example), you may use:
To grab a sequence of images, you may rather use:
If you have both Intel RealSense D435 and Occipital Structure Core, you can acquire color and depth frames simultaneously from both sensors.
Once tutorial-grabber-rgbd-D435-structurecore.cpp is built, you just need to run:
You should see something similar to the following:
It is also possible to grab images using OpenCV. You may find an example in tutorial-grabber-opencv.cpp.
Once tutorial-grabber-opencv.cpp is built, the binary usage is given by:
To just view images, run:
To grab single shot images (for camera calibration for example), you may use:
To grab a sequence of images, you may rather use:
It is also possible to grab images using CMU1394 SDK if you want to use a firewire camera under Windows. You may find an example in tutorial-grabber-CMU1394.cpp.
It is also possible to grab images using a Parrot Bebop 2 drone. You may find an example in tutorial-grabber-bebop2.cpp.
Once tutorial-grabber-bebop2.cpp is built, the binary usage is given by:
To just view images, run:
To grab single shot images (for camera calibration for example), you may use:
To grab a sequence of images, you may rather use:
You can chose to record HD 720p pictures from the drone (instead of default 480p) using –hd_resolution option :
With ViSP it also possible to get images from an input video stream. Supported formats are *.avi, *.mp4, *.mov, *.ogv, *.flv and many others... To this end we exploit OpenCV 3rd party.
The example below available in tutorial-video-reader.cpp shows how to consider an mpeg video stream.
The source code is the following:
We explain now the new lines that were introduced.
Include the header of the vpTime class that allows to measure time, and of the vpVideoReader class that allows to read a video stream.
Create an instance of a video reader.
Set the name of the video stream. Here videoname corresponds to a video file name location. For example we provide the file video.mpg located in the same folder than the executable.
The vpVideoReader class can also handle a sequence of images. For example, to read the following images:
you may use the following:
where you specify that each image number is coded with 4 digits. Here, we will use libpng or OpenCV to read PNG images. Supported image formats are PPM, PGM, PNG and JPEG.
Then as for any other grabber, you have to initialize the frame grabber using:
Then we enter in the while loop until the last image was not reached:
To get the next image in the stream, we just use:
To synchronize the video decoding with the video framerate, we measure the beginning time of each loop iteration:
The synchronization is done by waiting from the beginning of the iteration the corresponding time expressed in milliseconds by using:
Once tutorial-video-reader.cpp is built, the binary usage is given by:
To read the default video video.mpg, run:
To read an other video, let say my-video.mpg, you may use:
You are now ready to see how to continue with:
1.8.13