V5.15.08 problem with SetRGB()

ROOT
1

Hi Rooters,

I’ve moved to v5.15.08 and get a segmentation fault when I run the attached macro.

The attached macro is a section of a larger macro which sets the colours I want to use in a contour plot and works fine in v5.11.02.
The problem appears to be the col->SetRGB(double, double, double) command.

I can call it interactively:

TColor* col;
col = gROOT->GetColor(100);
col->SetRGB(0,0,0);

But it dies in the macro :(.

Does anyone have any ideas why the seg fault occurs and how I might correct the macro so it retains the same funtionality?

Thanks in advance,

Paul.
mycolor.C (354 Bytes)

2

Hi Paul,

It looks like ROOT colors are not initialized. Will your macro work if you call TColor::InitializeColors() in the beginning?

Cheers, Ilka

3

Hi,

Now I get:

Error: illegal pointer to class object col 0x0 295 mycolor.C:8:

If I just include:

col->InitializeColors();

Or the seg fault if I just include:

TColor::InitializeColors();

Any ideas?

Paul.
mycolor.C (414 Bytes)

4

Hi Paul,

No idea right now - I will investigate on Monday if nobody answers your question.

Cheers, Ilka

BTW, what happens if you create a canvas on the first line in your macro?

5

Running this macro which creates a canvas object before i set my colors has exactly the same pointer error.

void mycolor(char* name=“h_example”){
//Set up the colours I wish to use:
const Int_t ncol = 9;
Int_t colors[ncol];
TCanvas* tcan = new TCanvas(“myCanvas”,“myCanvas”,550,550);
TColor col;
Double_t dg=1.0/(1.0(Double_t)ncol);
// TColor::InitializeColors();
col->InitializeColors();
Double_t grey=0.;
for (Int_t i=0; i<ncol; i++) {
colors[i]= i+100;
col = gROOT->GetColor(colors[i]);
col->SetRGB(grey, grey, grey);
grey += dg;
}
}

6

The macro works in v5.14/00e if I remove the InitializeColors() line.

void mycolor(char* name=“h_example”){
//Set up the colours I wish to use:
const Int_t ncol = 3;
Int_t colors[ncol];
TCanvas* tcan = new TCanvas(“myCanvas”,“myCanvas”,550,550);
TColor col;
Double_t dg=1.0/(1.0(Double_t)ncol);
// TColor::InitializeColors();
// col->InitializeColors();
Double_t grey=0.;
for (Int_t i=0; i<ncol; i++) {
colors[i]= i+100;
col = gROOT->GetColor(colors[i]);
col->SetRGB(grey, grey, grey);
grey += dg;
}
}

7

Color management has changed. Now the colors above 100 are not created as before. Therefore gROOT->GetColor() returns 0 because the color does not exist. The following macro takes this into account:

{
   TF2 *f2 = new TF2("f2","0.1+1000*((1-(x-2)*(x-2))*(1-(y-2)*(y-2)))",1,3,1,3);   
   Int_t ncol = 50;
   Int_t colors[ncol];
   TColor *col;
   Double_t dg=1/(Double_t)ncol;
   Double_t grey=0;
   for (Int_t i=0; i<ncol; i++) {
      colors[i]= i+101;
      if (gROOT->GetColor(colors[i])) {
         gROOT->GetColor(colors[i])->SetRGB(grey, grey, grey);
      } else {
         TColor *c = new TColor(colors[i], grey, grey, grey);
      }
      grey = grey+dg;
   }
   f2->SetContour(ncol);
   gStyle->SetPalette(ncol,colors);
   f2->Draw("cont4 z");
}
8

Thanks, that has fixed it.