polytest1.C

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/// \file
/// \ingroup tutorial_graphics
/// \notebook
/// This macro is testing the "compacting" algorithm in TPadPainter.
/// It reduces the number of polygon's vertices using actual pixel coordinates.
///
/// \macro_image
///
/// It's not really useful, but just to test that the resulting polygon
/// is still reasonable. Initial number of points is 1000000, after "compression"
/// it's 523904 (with default canvas size, before you tried to resize it) - so almost half of
/// vertices were removed but you can still see the reasonable shape. If you resize
/// a canvas to a smaller size, the number of vertices after compression can be something like 5000 and even less.
/// It's easy to 'fool' this algorithm though in this particular case (ellipse is a kind of fringe case,
/// you can easily have a sequence of almost unique vertices (at a pixel level).
///
/// \macro_code
///
/// \author Timur Pocheptsov
 
// Includes for ACLiC.
#include <cassert>
#include <vector>
 
#include "TRandom.h"
#include "TCanvas.h"
#include "TError.h"
#include "Rtypes.h"
#include "TNamed.h"
#include "TMath.h"
 
class PolyTest1 : public TNamed, public TAttLine, public TAttFill {
public:
   PolyTest1(unsigned nVertices);
 
   void Paint(const Option_t *notUsed) override;
   void Reset(unsigned nVertices);
 
private:
   enum {
      kNPointsDefault = 10000 // minimal number of points.
   };
 
   std::vector<Double_t> fXs;
   std::vector<Double_t> fYs;
};
 
//_____________________________________________________________
PolyTest1::PolyTest1(unsigned nVertices) : TNamed("polygon_compression_test1", "polygon_compression_test1")
{
   Reset(nVertices);
}
 
//_____________________________________________________________
void PolyTest1::Reset(unsigned nVertices)
{
   // Some canvas must already exist by this point.
   assert(gPad != nullptr && "Reset, gPad is null");
   // We need a gRandom to exist.
   assert(gRandom != nullptr && "Reset, gRandom is null");
 
   if (nVertices < kNPointsDefault) {
      Warning("Reset", "resetting nVertices parameter to %u", unsigned(kNPointsDefault));
      nVertices = kNPointsDefault;
   }
 
   fXs.resize(nVertices);
   fYs.resize(nVertices);
 
   Double_t xMin = 0., xMax = 0., yMin = 0., yMax = 0.;
   gPad->GetRange(xMin, yMin, xMax, yMax);
   assert(xMax - xMin > 0 && yMax - yMin > 0 && "Reset, invalid canvas' ranges");
 
   const Double_t xCentre = xMin + 0.5 * (xMax - xMin);
   const Double_t yCentre = yMin + 0.5 * (yMax - yMin);
 
   const Double_t r = TMath::Min(xMax - xMin, yMax - yMin) * 0.8 / 2;
   const Double_t angle = TMath::TwoPi() / (nVertices - 1);
 
   for (unsigned i = 0; i < nVertices - 1; ++i) {
      const Double_t currR = r + gRandom->Rndm() * r * 0.01;
      fXs[i] = xCentre + currR * TMath::Cos(angle * i);
      fYs[i] = yCentre + currR * TMath::Sin(angle * i);
   }
 
   fXs[nVertices - 1] = fXs[0];
   fYs[nVertices - 1] = fYs[0];
}
 
//_____________________________________________________________
void PolyTest1::Paint(const Option_t * /*notUsed*/)
{
   assert(gPad != nullptr && "Paint, gPad is null");
 
   TAttFill::Modify();
   gPad->PaintFillArea((Int_t)fXs.size(), &fXs[0], &fYs[0]);
 
   TAttLine::Modify();
   gPad->PaintPolyLine((Int_t)fXs.size(), &fXs[0], &fYs[0]);
}
 
void polytest1()
{
   TCanvas *const cnv = new TCanvas;
   cnv->cd();
 
   PolyTest1 *polygon = new PolyTest1(1000000);
   polygon->SetLineColor(kBlue);
   polygon->SetFillColor(kRed);
   polygon->SetLineWidth(1);
   polygon->Draw(); // Attach a polygon to a canvas.
}