TColor, marker color, and png image bug

ROOT
1

Hello Everyone,

I have created a bunch of colors which I think look nice together and use them to make some plots.
I start at TColor number 4000 (arbitrary) and define about 20 colors or so.

The problem is when I save the canvas as a png (or as a jpg) the whole thing is washed out with one color.
The plot looks like this:

A1p_line_black.png1290×772 1.55 KB

However, if I set the graph’s marker color to standard black it works. I get what i expect:

A1p_marker_black.png1290×772 17.2 KB

Is this a bug or am I doing something wrong here?

Thanks in advance,
Whit

2

can you provide a small example ?
Have you tried to use smaller indices ? (not 4000) …

3

I have determined is has to do with using an alpha value not equal to 1.

Using the script below you can use color “BLAH” and there is no problem.
If you use the color “BLAH2” you should run into a problem with the resulting png file.

Int_t marker_bug(){

   TColor * color = new TColor(3998,0.2,0.05,0.7,"BLAH");
   TColor * color = new TColor(3999,0.2,0.05,0.7,"BLAH2",0.9);

   TCanvas * c1 = new TCanvas("c1","A Simple Graph with error bars",200,10,700,500);
   //c1->SetFillColor(42);
   c1->SetGrid();
   //c1->GetFrame()->SetFillColor(21);
   //c1->GetFrame()->SetBorderSize(12);
   const int n = 10;
   Double_t x[n]  = {-0.22, 0.05, 0.25, 0.35, 0.5, 0.61,0.7,0.85,0.89,0.95};
   Double_t y[n]  = {1,2.9,5.6,7.4,9,9.6,8.7,6.3,4.5,1};
   Double_t ex[n] = {.05,.1,.07,.07,.04,.05,.06,.07,.08,.05};
   Double_t ey[n] = {.8,.7,.6,.5,.4,.4,.5,.6,.7,.8};
   TGraphErrors * gr = new TGraphErrors(n,x,y,ex,ey);
   gr->SetTitle("TGraphErrors Example");
   //gr->SetMarkerColor(3999);
   gr->SetMarkerColor(3998);
   gr->SetMarkerStyle(20);
   gr->Draw("ALP");

   c1->SaveAs("marker_bug.png");
return(0);
}
4

yes it is connected with Alpha. I will check. You need transparency ?

5

I made a bug report: savannah.cern.ch/bugs/?98478