Visual Servoing Platform  version 3.5.1 under development (2022-11-26)

Example of dot tracking on an image sequence using vpDot.

* ViSP, open source Visual Servoing Platform software.
* Copyright (C) 2005 - 2019 by Inria. All rights reserved.
* This software is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
* See the file LICENSE.txt at the root directory of this source
* distribution for additional information about the GNU GPL.
* For using ViSP with software that can not be combined with the GNU
* GPL, please contact Inria about acquiring a ViSP Professional
* Edition License.
* See for more information.
* This software was developed at:
* Inria Rennes - Bretagne Atlantique
* Campus Universitaire de Beaulieu
* 35042 Rennes Cedex
* France
* If you have questions regarding the use of this file, please contact
* Inria at
* This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
* Description:
* Example of dot tracking.
* Authors:
* Eric Marchand
* Fabien Spindler
#include <visp3/core/vpConfig.h>
#include <visp3/core/vpDebug.h>
#include <iomanip>
#include <sstream>
#include <stdio.h>
#include <stdlib.h>
#if defined(VISP_HAVE_MODULE_BLOB) && \
(defined(VISP_HAVE_X11) || defined(VISP_HAVE_GTK) || defined(VISP_HAVE_GDI) || defined(VISP_HAVE_OPENCV))
#include <visp3/blob/vpDot.h>
#include <visp3/core/vpImage.h>
#include <visp3/core/vpImagePoint.h>
#include <visp3/core/vpIoTools.h>
#include <visp3/gui/vpDisplayGDI.h>
#include <visp3/gui/vpDisplayGTK.h>
#include <visp3/gui/vpDisplayOpenCV.h>
#include <visp3/gui/vpDisplayX.h>
#include <visp3/io/vpImageIo.h>
#include <visp3/io/vpParseArgv.h>
// List of allowed command line options
#define GETOPTARGS "cdf:i:n:p:s:h"
void usage(const char *name, const char *badparam, std::string ipath, std::string ppath, unsigned first,
unsigned nimages, unsigned step);
bool getOptions(int argc, const char **argv, std::string &ipath, std::string &ppath, unsigned &first, unsigned &nimages,
unsigned &step, bool &click_allowed, bool &display);
void usage(const char *name, const char *badparam, std::string ipath, std::string ppath, unsigned first,
unsigned nimages, unsigned step)
fprintf(stdout, "\n\
Test dot tracking.\n\
%s [-i <test image path>] [-p <personal image path>]\n\
[-f <first image>] [-n <number of images>] [-s <step>]\n\
[-c] [-d] [-h]\n",
fprintf(stdout, "\n\
OPTIONS: Default\n\
-i <input image path> %s\n\
Set image input path.\n\
From this path read images \n\
\"mire-2/image.%%04d.pgm\". These \n\
images come from ViSP-images-x.y.z.tar.gz available \n\
on the ViSP website.\n\
Setting the VISP_INPUT_IMAGE_PATH environment\n\
variable produces the same behaviour than using\n\
this option.\n\
-p <personal image path> %s\n\
Specify a personal sequence containing images \n\
to process.\n\
By image sequence, we mean one file per image.\n\
The following image file formats PNM (PGM P5, PPM P6)\n\
are supported. The format is selected by analysing \n\
the filename extension.\n\
Example : \"C:/Temp/ViSP-images/cube/image.%%04d.pgm\"\n\
%%04d is for the image numbering.\n\
-f <first image> %u\n\
First image number of the sequence.\n\
-n <number of images> %u\n\
Number of images to load from the sequence.\n\
-s <step> %u\n\
Step between two images.\n\
Disable the mouse click. Useful to automaze the \n\
execution of this program without humain intervention.\n\
-d \n\
Turn off the display.\n\
Print the help.\n",
ipath.c_str(), ppath.c_str(), first, nimages, step);
if (badparam)
fprintf(stdout, "\nERROR: Bad parameter [%s]\n", badparam);
bool getOptions(int argc, const char **argv, std::string &ipath, std::string &ppath, unsigned &first, unsigned &nimages,
unsigned &step, bool &click_allowed, bool &display)
const char *optarg_;
int c;
while ((c = vpParseArgv::parse(argc, argv, GETOPTARGS, &optarg_)) > 1) {
switch (c) {
case 'c':
click_allowed = false;
case 'd':
display = false;
case 'i':
ipath = optarg_;
case 'p':
ppath = optarg_;
case 'f':
first = (unsigned)atoi(optarg_);
case 'n':
nimages = (unsigned)atoi(optarg_);
case 's':
step = (unsigned)atoi(optarg_);
case 'h':
usage(argv[0], NULL, ipath, ppath, first, nimages, step);
return false;
usage(argv[0], optarg_, ipath, ppath, first, nimages, step);
return false;
if ((c == 1) || (c == -1)) {
// standalone param or error
usage(argv[0], NULL, ipath, ppath, first, nimages, step);
std::cerr << "ERROR: " << std::endl;
std::cerr << " Bad argument " << optarg_ << std::endl << std::endl;
return false;
return true;
int main(int argc, const char **argv)
try {
std::string env_ipath;
std::string opt_ipath;
std::string ipath;
std::string opt_ppath;
std::string dirname;
std::string filename;
unsigned opt_first = 1;
unsigned opt_nimages = 500;
unsigned opt_step = 1;
bool opt_click_allowed = true;
bool opt_display = true;
// Get the visp-images-data package path or VISP_INPUT_IMAGE_PATH
// environment variable value
// Set the default input path
if (!env_ipath.empty())
ipath = env_ipath;
// Read the command line options
if (getOptions(argc, argv, opt_ipath, opt_ppath, opt_first, opt_nimages, opt_step, opt_click_allowed,
opt_display) == false) {
// Get the option values
if (!opt_ipath.empty())
ipath = opt_ipath;
// Compare ipath and env_ipath. If they differ, we take into account
// the input path comming from the command line option
if (!opt_ipath.empty() && !env_ipath.empty() && opt_ppath.empty()) {
if (ipath != env_ipath) {
std::cout << std::endl << "WARNING: " << std::endl;
std::cout << " Since -i <visp image path=" << ipath << "> "
<< " is different from VISP_IMAGE_PATH=" << env_ipath << std::endl
<< " we skip the environment variable." << std::endl;
// Test if an input path is set
if (opt_ipath.empty() && env_ipath.empty() && opt_ppath.empty()) {
usage(argv[0], NULL, ipath, opt_ppath, opt_first, opt_nimages, opt_step);
std::cerr << std::endl << "ERROR:" << std::endl;
std::cerr << " Use -i <visp image path> option or set VISP_INPUT_IMAGE_PATH " << std::endl
<< " environment variable to specify the location of the " << std::endl
<< " image path where test images are located." << std::endl
<< " Use -p <personal image path> option if you want to " << std::endl
<< " use personal images." << std::endl
<< std::endl;
// Declare an image, this is a gray level image (unsigned char)
// it size is not defined yet, it will be defined when the image will
// read on the disk
unsigned iter = opt_first;
std::ostringstream s;
char cfilename[FILENAME_MAX];
if (opt_ppath.empty()) {
// Warning :
// the image sequence is not provided with the ViSP package
// therefore the program will return you an error :
// !! vpImageIoPnm.cpp: readPGM(#210) :couldn't read file
// ViSP-images/mire-2/image.0001.pgm
// !! vpDotExample.cpp: main(#95) :Error while reading the image
// terminate called after throwing an instance of 'vpImageException'
// The sequence is available on the visp www site
// in the download section. It is named "ViSP-images.tar.gz"
// Set the path location of the image sequence
dirname = vpIoTools::createFilePath(ipath, "mire-2");
// Build the name of the image file
s.setf(std::ios::right, std::ios::adjustfield);
s << "image." << std::setw(4) << std::setfill('0') << iter << ".pgm";
filename = vpIoTools::createFilePath(dirname, s.str());
} else {
sprintf(cfilename, opt_ppath.c_str(), iter);
filename = cfilename;
// Read the PGM image named "filename" on the disk, and put the
// bitmap into the image structure I. I is initialized to the
// correct size
// exception readPGM may throw various exception if, for example,
// the file does not exist, or if the memory cannot be allocated
try {
vpCTRACE << "Load: " << filename << std::endl;
vpImageIo::read(I, filename);
} catch (...) {
// an exception is throwned if an exception from readPGM has been
// catched here this will result in the end of the program Note that
// another error message has been printed from readPGM to give more
// information about the error
std::cerr << std::endl << "ERROR:" << std::endl;
std::cerr << " Cannot read " << filename << std::endl;
std::cerr << " Check your -i " << ipath << " option " << std::endl
<< " or VISP_INPUT_IMAGE_PATH environment variable." << std::endl;
// We open a window using either X11, GTK or GDI.
#if defined VISP_HAVE_X11
vpDisplayX display;
#elif defined VISP_HAVE_GTK
vpDisplayGTK display;
#elif defined VISP_HAVE_GDI
vpDisplayGDI display;
#elif defined VISP_HAVE_OPENCV
vpDisplayOpenCV display;
if (opt_display) {
// Display size is automatically defined by the image (I) size
display.init(I, 100, 100, "Display...");
// Display the image
// The image class has a member that specify a pointer toward
// the display that has been initialized in the display declaration
// therefore is is no longuer necessary to make a reference to the
// display variable.
// by using setGraphics, we request to see the all the pixel of the dot
vpDot d;
if (opt_display) {
// by using setGraphics, we request to see the all the pixel of the dot
// in green on the screen.
// It uses the overlay image plane.
// The default of this setting is that it is time consumming
} else {
// we also request to compute the dot moment m00, m10, m01, m11, m20, m02
if (opt_display && opt_click_allowed) {
// tracking is initalized
// if no other parameters are given to the iniTracking(..) method
// a right mouse click on the dot is expected
std::cout << "Click on a white dot you want to track..." << std::endl;
} else {
// dot location can also be specified explicitely in the
// initTracking method : d.initTracking(I,ip) where ip is the
// image point from which the dot is searched
d.initTracking(I, ip);
while (iter < opt_first + opt_nimages * opt_step) {
// set the new image name
if (opt_ppath.empty()) {
s << "image." << std::setw(4) << std::setfill('0') << iter << ".pgm";
filename = vpIoTools::createFilePath(dirname, s.str());
} else {
sprintf(cfilename, opt_ppath.c_str(), iter);
filename = cfilename;
// read the image
std::cout << "read : " << filename << std::endl;
vpImageIo::read(I, filename);
if (opt_display) {
// Display the image
std::cout << "Tracking on image: " << filename << std::endl;
// track the dot
double time = vpTime::measureTimeMs();
std::cout << "COG (" << vpTime::measureTimeMs() - time << " ms): " << std::endl;
cog = d.getCog();
std::cout << cog.get_u() << " " << cog.get_v() << std::endl;
std::cout << "Size:" << std::endl;
std::cout << " w: " << d.getWidth() << " h: " << d.getHeight() << std::endl;
std::cout << "Area: " << d.getArea() << std::endl;
std::cout << "Centered normalized moments nij:" << std::endl;
std::cout << " n20: " << d.get_nij()[0] << std::endl;
std::cout << " n11: " << d.get_nij()[1] << std::endl;
std::cout << " n02: " << d.get_nij()[2] << std::endl;
if (0) {
std::list<vpImagePoint> edges = d.getEdges();
std::list<vpImagePoint>::const_iterator it;
for (it = edges.begin(); it != edges.end(); ++it) {
if (opt_display) {
// display a red cross (size 10) in the image at the dot center
// of gravity location
// flush the X11 buffer
if (opt_display && opt_click_allowed) {
std::cout << "\nA click to exit..." << std::endl;
// Wait for a blocking mouse click
} catch (const vpException &e) {
std::cout << "Catch an exception: " << e << std::endl;
#include <iostream>
int main()
std::cout << "visp_blob module or X11, GTK, GDI or OpenCV display "
"functionalities are required..."
<< std::endl;
static const vpColor red
Definition: vpColor.h:217
static const vpColor blue
Definition: vpColor.h:223
Display for windows using GDI (available on any windows 32 platform).
Definition: vpDisplayGDI.h:129
The vpDisplayGTK allows to display image using the GTK 3rd party library. Thus to enable this class G...
Definition: vpDisplayGTK.h:135
The vpDisplayOpenCV allows to display image using the OpenCV library. Thus to enable this class OpenC...
Use the X11 console to display images on unix-like OS. Thus to enable this class X11 should be instal...
Definition: vpDisplayX.h:135
static bool getClick(const vpImage< unsigned char > &I, bool blocking=true)
static void display(const vpImage< unsigned char > &I)
static void displayCross(const vpImage< unsigned char > &I, const vpImagePoint &ip, unsigned int size, const vpColor &color, unsigned int thickness=1)
unsigned int getHeight() const
Definition: vpDisplay.h:240
static void flush(const vpImage< unsigned char > &I)
static void displayPoint(const vpImage< unsigned char > &I, const vpImagePoint &ip, const vpColor &color, unsigned int thickness=1)
unsigned int getWidth() const
Definition: vpDisplay.h:245
This tracker is meant to track a dot (connected pixels with same gray level) on a vpImage.
Definition: vpDot.h:116
Definition: vpDot.h:124
error that can be emited by ViSP classes.
Definition: vpException.h:72
static void read(vpImage< unsigned char > &I, const std::string &filename, int backend=IO_DEFAULT_BACKEND)
Definition: vpImageIo.cpp:148
Class that defines a 2D point in an image. This class is useful for image processing and stores only ...
Definition: vpImagePoint.h:89
double get_u() const
Definition: vpImagePoint.h:143
void set_u(double u)
Definition: vpImagePoint.h:335
void set_v(double v)
Definition: vpImagePoint.h:346
double get_v() const
Definition: vpImagePoint.h:154
static std::string getViSPImagesDataPath()
Definition: vpIoTools.cpp:1378
static std::string createFilePath(const std::string &parent, const std::string &child)
Definition: vpIoTools.cpp:1696
static bool parse(int *argcPtr, const char **argv, vpArgvInfo *argTable, int flags)
Definition: vpParseArgv.cpp:69
#define vpCTRACE
Definition: vpDebug.h:338
VISP_EXPORT double measureTimeMs()