Introduction

This tutorial follows Tutorial: Introduction to color segmentation using HSV color scale.

Note that all the material (source code and images) described in this tutorial is part of ViSP source code (in tutorial/segmentation/color folder) and could be found in https://github.com/lagadic/visp/tree/master/tutorial/segmentation/color.

HSV Range tuner tool

In the previous tutorial (see Tutorial: Introduction to color segmentation using HSV color scale), we used the following lines to determine HSV low/high range values in hsv_range vector:

  int h = 14, s = 255, v = 209;
  int offset = 30;
  int h_low = std::max<int>(0, h - offset), h_high = std::min<int>(h + offset, 255);
  int s_low = std::max<int>(0, s - offset), s_high = std::min<int>(s + offset, 255);
  int v_low = std::max<int>(0, v - offset), v_high = std::min<int>(v + offset, 255);
  std::vector<int> hsv_range;
  hsv_range.push_back(h_low);
  hsv_range.push_back(h_high);
  hsv_range.push_back(s_low);
  hsv_range.push_back(s_high);
  hsv_range.push_back(v_low);
  hsv_range.push_back(v_high);

Then this vector was used to determine the pixels that were in the HSV low/high ranges in oder to compute a mask:

  vpImage<unsigned char> mask(height, width);
  vpImageTools::inRange(reinterpret_cast<unsigned char *>(H.bitmap),
                        reinterpret_cast<unsigned char *>(S.bitmap),
                        reinterpret_cast<unsigned char *>(V.bitmap),
                        hsv_range,
                        reinterpret_cast<unsigned char *>(mask.bitmap),
                        mask.getSize());

In tutorial-hsv-range-tuner.cpp we propose a tool that allows to set these HSV low/high values either using a trackbar or by clicking on a pixel in the image before fine tuning the range values with the trackbar.

Once build, you can either use this tool on a single image like

$ cd $VISP_WS/visp-build/tutorial/segmentation/color
$ ./tutorial-hsv-range-tuner --image ballons.jpg

or if you have a Realsense camera, proceed with the live stream simply by running
```
$ ./tutorial-hsv-range-tuner
```

To use this tool, in the "Current frame" window:

Left click allows to set the HSV low/high values in the trackbar
Middle click allows to print the RGB and HSV values corresponding to the clicked point
Right mouse click allows to save the HSV low/high range values in a yaml file. By default this file is saved in calib/hsv-thresholds.yml. Hereafter we provide a possible content:
```
$ cat calib/hsv-thresholds.yml
# File created 2024/04/03 17:28:10
rows: 6
cols: 1
data:
  - [0]
  - [64]
  - [222]
  - [255]
  - [128]
  - [242]
```

Next tutorial

You are now ready to see how to continue with Tutorial: Live color segmentation using HSV color scale.

Table of Contents

Introduction

HSV Range tuner tool

Next tutorial