Dear Enrico,
That’s the thing, I was making plots for my last publication at the beginning of the month and it was fine. Last week I tried to make plots for a presentation and the PNG and JPG turned blue. This was a sudden problem that I’ve never experienced before with the same ROOT version.
~Doug
Douglas Rodriguez, PhD
I am afraid we do not know what might have caused the problem and without being able to reproduce it we cannot debug it on our side 
Hi Doug,
As it seems to work in the old days on that machine, something should have in between. The MacOS version ? the ROOT version ?
Cheers,
Olivier
I have the same problem when updated to root_v6.20.04 in MacOS Majave 10.14, and It can be solved temporarily in batch mode without showing the canvas when running the code：
(1) adding gROOT->SetBatch(1); // set to batch mode->do not display graphics
or (2) root -l -b yourcode.C
then maybe you create the canvas.png in batch mode.
if you want to show the canvas (the image actually) when running the code, please add the following code:
//c->SaveAs(“canvas.png”); //if you have set this name
// back to graphics mode
gROOT->SetBatch(0);
// create an image from image file
TImage *ps = TImage::Open(“canvas.png”); //refer to #include “TImage.h”
if (!ps)
{
printf(“No image found\n”);
return;
}
new TCanvas(“png”, “display image in canvas”, 200, 10, 400, 400);
ps->Draw(“xxx”);