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3D histogram

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LaurentBerger 7 years ago
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  1. 157
      doc/tutorials/viz/histo3D/histo3D.markdown
  2. BIN
      doc/tutorials/viz/histo3D/images/histo50.png
  3. 8
      doc/tutorials/viz/table_of_content_viz.markdown
  4. 170
      samples/cpp/tutorial_code/viz/histo3D.cpp

157
doc/tutorials/viz/histo3D/histo3D.markdown
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Creating a 3D histogram {#tutorial_histo3D}
================
Goal
----
In this tutorial you will learn how to
- Create your own callback keyboard function for viz window.
- Show your 3D histogram in a viz window.
Code
----
You can download the code from [here ](https://github.com/opencv/opencv/tree/master/samples/cpp/tutorial_code/viz/histo3D.cpp).
@include samples/cpp/tutorial_code/viz/histo3D.cpp
Explanation
-----------
Here is the general structure of the program:
- You can give full path to an image in command line
@code{.cpp}
CommandLineParser parser(argc, argv, keys);
if (parser.has("help"))
{
parser.printMessage();
return 0;
}
String nomFic = parser.get<String>(0);
Mat img;
if (nomFic.length() != 0)
{
img = imread(nomFic, IMREAD_COLOR);
if (img.empty())
{
cout << "Image does not exist!";
return 0;
}
}
@endcode
or without path, a synthetic image is generated with pixel values are a gaussian distribution center(60+/-10,40+/-5,50+/-20) in first quadrant,
(160+/-20,10+/-5,50+/-10) in second quadrant, (90+/-10,100+/-20,50+/-20) in third quadrant, (100+/-10,10+/-5,150+/-40) in last quadrant.
@code{.cpp}
else
{
img = Mat(512,512,CV_8UC3);
parser.printMessage();
RNG r;
r.fill(img(Rect(0, 0, 256, 256)), RNG::NORMAL, Vec3b(60, 40, 50), Vec3b(10, 5, 20));
r.fill(img(Rect(256, 0, 256, 256)), RNG::NORMAL, Vec3b(160, 10, 50), Vec3b(20, 5, 10));
r.fill(img(Rect(0, 256, 256, 256)), RNG::NORMAL, Vec3b(90, 100, 50), Vec3b(10, 20, 20));
r.fill(img(Rect(256, 256, 256, 256)), RNG::NORMAL, Vec3b(100, 10, 150), Vec3b(10, 5, 40));
}
@endcode
Image tridimensional histogram is calculated using opencv calcHist and normalize between 0 and 100.
@code{.cpp}
float hRange[] = { 0, 256 };
const float* etendu[] = { hRange, hRange,hRange };
int hBins = 32;
int tailleHist[] = { hBins, hBins , hBins };
int canaux[] = { 2, 1,0 };
calcHist(&img, 1, canaux, Mat(), h.histogram, 3, tailleHist, etendu, true, false);
normalize(h.histogram, h.histogram, 100.0/(img.total()), 0, cv::NormTypes::NORM_MINMAX, -1, cv::Mat());
minMaxIdx(h.histogram,NULL,&h.maxH,NULL,NULL);
@endcode
channel are 2, 1 and 0 to synchronise color with Viz axis color in objetc viz::WCoordinateSystem.
A slidebar is inserted in image window. Init slidebar value is 90, it means that only histogram cell greater than 9/100000.0 (23 pixels for an 512X512 pixels) will be display.
@code{.cpp}
namedWindow("Image");
imshow("Image",img);
AddSlidebar("threshold","Image",0,100,h.seuil,&h.seuil, UpdateThreshold,&h);
waitKey(30);
@endcode
We are ready to open a viz window with a callback function to capture keyboard event in viz window. Using Viz::spinonce enable keyboard event to be capture in imshow window too.
@code{.cpp}
h.fen3D = new viz::Viz3d("3D Histogram");
h.nbWidget=0;
h.fen3D->registerKeyboardCallback(KeyboardViz3d,&h);
DrawHistogram3D(h);
while (h.code!=27)
{
h.fen3D->spinOnce(1);
if (h.status)
DrawHistogram3D(h);
if (h.code!=27)
h.code= waitKey(30);
}
@endcode
The function DrawHistogram3D processes histogram Mat to display it in a Viz window. Number of plan, row and column in three dimensional Mat ca be found using this code :
@code{.cpp}
int planSize = h.histogram.step1(0);
int cols = h.histogram.step1(1);
int rows = planSize / cols;
int plans = h.histogram.total() / planSize;
h.fen3D->removeAllWidgets();
h.nbWidget=0;
if (h.nbWidget==0)
h.fen3D->showWidget("Axis", viz::WCoordinateSystem(10));
@endcode
To get histogram value at a specific location we use at method with three arguments k, i and j where k is plane number, i row number and j column number.
@code{.cpp}
for (int k = 0; k < plans; k++)
{
for (int i = 0; i < rows; i++)
{
for (int j = 0; j < cols; j++)
{
double x = h.histogram.at<float>(k, i, j);
if (x >= h.threshold)
{
double r=std::max(x/h.maxH,0.1);
viz::WCube s(Point3d(k - r / 2, i - r / 2, j - r / 2), Point3d(k + r / 2, i + r / 2, j + r / 2), false, viz::Color(j / double(plans) * 255, i / double(rows) * 255, k / double(cols) * 255));
h.fen3D->showWidget(format("I3d%d", h.nbWidget++), s);
}
}
}
}
@endcode
- Callback function
Principle are as mouse callback function. Key code pressed is in field code of class viz::KeyboardEvent.
@code{.cpp}
void KeyboardViz3d(const viz::KeyboardEvent &w, void *t)
{
Histo3DData *x=(Histo3DData *)t;
if (w.action)
cout << "you pressed "<< w.symbol<< " in viz window "<<x->fen3D->getWindowName()<<"\n";
x->code= w.code;
switch (w.code) {
case '/':
x->status=true;
x->threshold *= 0.9;
break;
case '*':
x->status = true;
x->threshold *= 1.1;
break;
}
if (x->status)
{
cout << x->threshold << "\n";
DrawHistogram3D(*x);
}
}
@endcode
Results
-------
Here is the result of the program with no argument and threshold equal to 50.
![](images/histo50.png)

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doc/tutorials/viz/histo3D/images/histo50.png
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8
doc/tutorials/viz/table_of_content_viz.markdown
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@ -32,3 +32,11 @@ OpenCV Viz {#tutorial_table_of_content_viz}
*Author:* Ozan Tonkal
You will learn how to create your own widgets.
- @subpage tutorial_histo3D
*Compatibility:* \> OpenCV 3.0.0
*Author:* Laurent Berger
You will learn how to plot a 3D histogram.

170
samples/cpp/tutorial_code/viz/histo3D.cpp
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#include <opencv2/opencv.hpp>
#include <iostream>
using namespace std;
using namespace cv;
#ifdef HAVE_OPENCV_VIZ
const String keys =
"{Aide h usage ? help | | print this message }"
"{@arg1 | | Full path to color imag (3 channels)}"
;
struct Histo3DData {
Mat histogram;
int seuil;
double threshold;
Ptr<viz::Viz3d> fen3D;
int nbWidget;
bool status;
double maxH;
int code;
};
void DrawHistogram3D(Histo3DData &);
void AddSlidebar(String sliderName, String windowName, int sliderMin, int sliderMax, int valeurDefaut, int *sliderVal, void(*f)(int, void *), void *r);
void UpdateThreshold(int , void * r);
void KeyboardViz3d(const viz::KeyboardEvent &w, void *t);
void DrawHistogram3D(Histo3DData &h)
{
int planSize = h.histogram.step1(0);
int cols = h.histogram.step1(1);
int rows = planSize / cols;
int plans = h.histogram.total() / planSize;
h.fen3D->removeAllWidgets();
h.nbWidget=0;
if (h.nbWidget==0)
h.fen3D->showWidget("Axis", viz::WCoordinateSystem(10));
for (int k = 0; k < plans; k++)
{
for (int i = 0; i < rows; i++)
{
for (int j = 0; j < cols; j++)
{
double x = h.histogram.at<float>(k, i, j);
if (x >= h.threshold)
{
double r=std::max(x/h.maxH,0.1);
viz::WCube s(Point3d(k - r / 2, i - r / 2, j - r / 2), Point3d(k + r / 2, i + r / 2, j + r / 2), false, viz::Color(j / double(plans) * 255, i / double(rows) * 255, k / double(cols) * 255));
h.fen3D->showWidget(format("I3d%d", h.nbWidget++), s);
}
}
}
}
h.status = false;
}
void KeyboardViz3d(const viz::KeyboardEvent &w, void *t)
{
Histo3DData *x=(Histo3DData *)t;
if (w.action)
cout << "you pressed "<< w.symbol<< " in viz window "<<x->fen3D->getWindowName()<<"\n";
x->code= w.code;
switch (w.code) {
case '/':
x->status=true;
x->threshold *= 0.9;
break;
case '*':
x->status = true;
x->threshold *= 1.1;
break;
}
if (x->status)
{
cout << x->threshold << "\n";
DrawHistogram3D(*x);
}
}
void AddSlidebar(String sliderName, String windowName, int sliderMin, int sliderMax, int defaultSlider, int *sliderVal, void(*f)(int, void *), void *r)
{
createTrackbar(sliderName, windowName, sliderVal, 1, f, r);
setTrackbarMin(sliderName, windowName, sliderMin);
setTrackbarMax(sliderName, windowName, sliderMax);
setTrackbarPos(sliderName, windowName, defaultSlider);
}
void UpdateThreshold(int , void * r)
{
Histo3DData *h = (Histo3DData *)r;
h->status=true;
h->threshold = h->seuil/1000000.0;
cout<<"Widget : "<<h->nbWidget<<","<< h->threshold<<"\n";
}
int main (int argc,char **argv)
{
CommandLineParser parser(argc, argv, keys);
if (parser.has("help"))
{
parser.printMessage();
return 0;
}
String nomFic = parser.get<String>(0);
Mat img;
if (nomFic.length() != 0)
{
img = imread(nomFic, IMREAD_COLOR);
if (img.empty())
{
cout << "Image does not exist!";
return 0;
}
}
else
{
img = Mat(512,512,CV_8UC3);
parser.printMessage();
RNG r;
r.fill(img(Rect(0, 0, 256, 256)), RNG::NORMAL, Vec3b(60, 40, 50), Vec3b(10, 5, 20));
r.fill(img(Rect(256, 0, 256, 256)), RNG::NORMAL, Vec3b(160, 10, 50), Vec3b(20, 5, 10));
r.fill(img(Rect(0, 256, 256, 256)), RNG::NORMAL, Vec3b(90, 100, 50), Vec3b(10, 20, 20));
r.fill(img(Rect(256, 256, 256, 256)), RNG::NORMAL, Vec3b(100, 10, 150), Vec3b(10, 5, 40));
}
Histo3DData h;
h.status=true;
h.seuil=90;
h.threshold= h.seuil/1000000.0;
float hRange[] = { 0, 256 };
const float* etendu[] = { hRange, hRange,hRange };
int hBins = 32;
int histSize[] = { hBins, hBins , hBins };
int channel[] = { 2, 1,0 };
calcHist(&img, 1, channel, Mat(), h.histogram, 3, histSize, etendu, true, false);
normalize(h.histogram, h.histogram, 100.0/(img.total()), 0, NORM_MINMAX, -1, Mat());
minMaxIdx(h.histogram,NULL,&h.maxH,NULL,NULL);
namedWindow("Image");
imshow("Image",img);
AddSlidebar("threshold","Image",0,100,h.seuil,&h.seuil, UpdateThreshold,&h);
waitKey(30);
h.fen3D = new viz::Viz3d("3D Histogram");
h.nbWidget=0;
h.fen3D->registerKeyboardCallback(KeyboardViz3d,&h);
DrawHistogram3D(h);
while (h.code!=27)
{
h.fen3D->spinOnce(1);
if (h.status)
DrawHistogram3D(h);
if (h.code!=27)
h.code= waitKey(30);
}
return 0;
}
#else
int main(int argc, char **argv)
{
cout << " you need VIZ module\n";
return 0;
}
#endif
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