RuntimeError: could not open display

[vlad-wonderkidstudio]

After installed on the command line CentOS server, when I try to run any OCRopus command, I get the following error:

$ ./ocropus-nlbin -h
Traceback (most recent call last):
 File "./ocropus-nlbin", line 5, in <module>
   from pylab import *
 File "/usr/lib64/python2.7/site-packages/pylab.py", line 1, in <module>
   from matplotlib.pylab import *
 File "/usr/lib64/python2.7/site-packages/matplotlib/pylab.py", line 265, in <module>
   from matplotlib.pyplot import *
 File "/usr/lib64/python2.7/site-packages/matplotlib/pyplot.py", line 97, in <module>
   _backend_mod, new_figure_manager, draw_if_interactive, _show = pylab_setup()
 File "/usr/lib64/python2.7/site-packages/matplotlib/backends/__init__.py", line 25, in pylab_setup
   globals(),locals(),[backend_name])
 File "/usr/lib64/python2.7/site-packages/matplotlib/backends/backend_gtkagg.py", line 10, in <module>
   from matplotlib.backends.backend_gtk import gtk, FigureManagerGTK, FigureCanvasGTK,\
 File "/usr/lib64/python2.7/site-packages/matplotlib/backends/backend_gtk.py", line 13, in <module>
   import gtk; gdk = gtk.gdk
 File "/usr/lib64/python2.7/site-packages/gtk-2.0/gtk/__init__.py", line 64, in <module>
   _init()
 File "/usr/lib64/python2.7/site-packages/gtk-2.0/gtk/__init__.py", line 52, in _init
   _gtk.init_check()
RuntimeError: could not open display

Expected Behavior

On my home Ubuntu within Gnome command line it works just fine.

Current Behavior

Possible Solution

Steps to Reproduce (for bugs)

1. Install on CentOS command-line only server (without display)
2. Run any command, like $ ./ocropus-nlbin -h
3. Get the error

Your Environment

• Python version: 2.7.5

• Git revision of ocropy:
  commit 358df8d
  Merge: dacf0fc e016e74
  Author: Philipp Zumstein zuphilip@users.noreply.github.com
  Date: Mon May 22 22:38:33 2017 +0200

  Merge pull request Delete unused function bounding_box in ocropus-linegen #219 from tmbdev/del-bbox-func

  Delete unused function bounding_box in ocropus-linegen

• Operating System and version:
  CentOS Linux release 7.3.1611 (Core)

[zuphilip]

The error looks like the display is not found for matplot, and indeed you write that you are using ocropy on the command line CentOS server. You can try to set export MPLBACKEND="agg" as it is also done in the CircleCI file.

[vlad-wonderkidstudio]

I tried to do so. After this I launched:
./ocropus-nlbin -h
And it just hangs (I can type texts in the console and anything, but no answer from the program).
After I pressed CTRL+C I got this message:

Traceback (most recent call last):
  File "./ocropus-nlbin", line 5, in <module>
    from pylab import *
  File "/usr/lib64/python2.7/site-packages/pylab.py", line 1, in <module>
    from matplotlib.pylab import *
  File "/usr/lib64/python2.7/site-packages/matplotlib/__init__.py", line 151, in <module>
    from matplotlib.rcsetup import (defaultParams,
  File "/usr/lib64/python2.7/site-packages/matplotlib/rcsetup.py", line 20, in <module>
    from matplotlib.colors import is_color_like
  File "/usr/lib64/python2.7/site-packages/matplotlib/colors.py", line 52, in <module>
    import numpy as np
  File "/usr/lib64/python2.7/site-packages/numpy/__init__.py", line 153, in <module>
    import polynomial
  File "/usr/lib64/python2.7/site-packages/numpy/polynomial/__init__.py", line 18, in <module>
    from polynomial import Polynomial
  File "/usr/lib64/python2.7/site-packages/numpy/polynomial/polynomial.py", line 54, in <module>
    """
KeyboardInterrupt

[zuphilip]

Hm... I have no experience with CentOS. Maybe @kba has some ideas?

[kba]

Hard to say w/o running a CentOS image. numpy/scipy/matplotlib can be tricky at times because of location of compiled libs etc.

Maybe run ocropus w/ docker?

[stweil]

Isn't it normal behavior that no display is found if you run on a host which only has command line installed? If I have a program which requires a display I'd install display support (for example X Windows on Linux).

[kba]

Isn't it normal behavior that no display is found if you run on a host which only has command line installed?

That was the initial issue, solved by setting Matplotlib's backend. The second issue is something different.

[vlad-wonderkidstudio]

@kba
How can I run it with docker?

[zuphilip]

You can use this docker image: https://hub.docker.com/r/kbai/ocropy/

[zuphilip]

@vlad-wonderkidstudio Did you find a solution for your CentOS?