Maximum canvas size in pixels

[Marek_Bombara]

Hello,

I try to plot a canvas with hundreds of histograms and save it as .png file. The width of the canvas is set to 1270 and the height depends on the histogram number. I have spotted that the final .png plot cannot have the height > 32000. If it would be bigger, some of the histograms will be missing in the plot. 32000 seems to be maximum canvas height in pixels.

My questions are: what is the origin of this maximum value and is it possible to create a plot with height more than 32000 pixels? Thank you.

Best regards,
Marek

[eguiraud]

Hi,
I cannot answer your question (maybe @bellenot or @couet can) but reading your post I cannot help but wonder whether it wouldn’t be more practical for you to save several different png images and only merge them together in a second step (with an external tool like gimp or imagemagick) if you really need it.

[bellenot]

You can try in batch mode (to avoid X11 errors), but you might have memory issues anyway… I would suggest to follow what @eguiraud suggested

[Marek_Bombara]

Hi Guys,

thanks for the fast response. The plot should be created automatically after each run - it is an output of the online data taking in the experiment.

I might try to do what Enrico has suggested skipping the second step, if no solution will be found.

Thanks anyway,
Marek

[eguiraud]

Note that merging of png’s can easily done programmatically. For example (just because this is what I know, not saying it’s the best solution)

convert image1.png image2.png output.pdf

concatenates the png images into a pdf file.
Good luck,
Enrico

[couet]

seems fine in batch mode

$ root -b
   -----------------------------------------------------------------
  | Welcome to ROOT 6.11/01                     http://root.cern.ch |
  |                                    (c) 1995-2017, The ROOT Team |
  | Built for macosx64                                              |
  | From heads/master@v6-09-02-1537-ge08851a, Jun 30 2017, 14:41:02 |
  | Try '.help', '.demo', '.license', '.credits', '.quit'/'.q'      |
   -----------------------------------------------------------------

root [0] TCanvas *c = new TCanvas("c","c",1270,32000)
(TCanvas *) 0x7f9c7496b4f0
root [1] hpx->Draw()
root [2] c->Print("bigcanvas.png");
Info in <TCanvas::Print>: png file bigcanvas.png has been created

[Marek_Bombara]

Hi Olivier,

yes I can confirm, it works in batch mode for me as well. Thank you vey much for your help!

Cheers,
Marek