psconvert: gs options passed via -C doesn't override internally hardcoded options

[uliw]

Edit by @seisman: The issue was initially reported to the PyGMT repository, but it turns out to be an GMT issue, so I transferred it here.

To reproduce the issue in the GMT CLI, try the following:

gmt psbasemap -R0/10/0/10 -JX10c -Baf > map.ps
gmt psconvert map.ps -C-dMaxBitmap=2000000 -S

The output is

gs -q -dNOPAUSE -dBATCH -dNOSAFER -dSCANCONVERTERTYPE=2 -dMaxBitmap=2000000 -dMaxBitmap=2147483647 -dUseFastColor=true -dGraphicsAlphaBits=2 -dTextAlphaBits=4 -sDEVICE=jpeg -dJPEGQ=90 -g2480x3509 -r300 -sOutputFile='map.jpg' './psconvert_3324091d.eps'

---

Description of the problem

Specifying ghostcript options in the figure command like this:

fig.savefig("foo.pd",
            gs_option="-dMaxBitmap=2000000,
            ) 

will pass the option to the ghopstcript process. However it will do so in front of the default values, so that the custom options are nullified.

Minimal Complete Verifiable Example

I only noticed because the psconvert step fails with an error. If this can be traced without creating a ginormous plot file, the above commands should be sufficient.

Full error message

pygmt.exceptions.GMTCLibError: Module 'psconvert' failed with status code 79:
psconvert [ERROR]: System call [gs -q -dNOSAFER -dNOPAUSE -dBATCH -sDEVICE=bbox -DPSL_no_pagefill -dMaxBitmap=20000000000, -dMaxBitmap=2147483647 -dUseFastColor=true '/home/uliw/.gmt/sessions/gmt_session.25132/gmt_1.ps-' 2> '/home/uliw/.gmt/sessions/gmt_session.25132/psconvert_25132c.bb'] returned error 256.

System information

PyGMT information:
  version: v0.18.0
System information:
  python: 3.14.3 | packaged by conda-forge | (main, Feb  9 2026, 21:56:02) [GCC 14.3.0]
  executable: /home/uliw/miniforge3/envs/p314/bin/python
  machine: Linux-6.19.2-1-default-x86_64-with-glibc2.42
Dependency information:
  numpy: 2.4.3
  pandas: 3.0.2
  xarray: 2026.2.0
  packaging: 26.0
  contextily: None
  geopandas: 1.1.3
  IPython: None
  pyarrow: None
  rioxarray: None
  gdal: 3.12.3
  ghostscript: 10.07.0
GMT library information:
  version: 6.6.0
  padding: 2
  share dir: /home/uliw/miniforge3/envs/p314/share/gmt
  plugin dir: /home/uliw/miniforge3/envs/p314/lib/gmt/plugins
  library path: /home/uliw/miniforge3/envs/p314/lib/libgmt.so
  cores: 32
  grid layout: rows
  image layout: 
  binary version: 6.6.0

[weiji14]

Hmm yeah, so that -dMaxBitmap=2147483647 argument seems to be hardcoded in upstream GMT at https://github.com/GenericMappingTools/gmt/blame/9880a3118ebbcf7a1cb0115f832e8b07c2da47c9/src/psconvert.c#L1817.

add_to_list (Ctrl->C.arg, "-dMaxBitmap=2147483647");	/* Add this as GS option to fix bug in GS */

I'm trying to find context on what that 'bug in GS (ghostscript)' is, since it was made >10 years ago (cbd67e1), going back to at least GMT 5. It seems that @remkos originally used -dMaxBitmap=100000000 for just psconvert ... -TG in 70e792e, and that number got increased to 2147483647 = 2^31-1 at some point, and applied to all psconvert operations.

Did you want to set a higher or lower dMaxBitmap? I see you mentioned -dMaxBitmap=2000000 first, but your error message shows -dMaxBitmap=20000000000. Either way, we probably need to handle this in GMT upstream, by unhardcoding the value somehow. cc @seisman.

[uliw]

I am trying to generate a high res map in poster format, but the process fails, even so the system has plenty of free memory. Reading https://ghostscript.readthedocs.io/en/latest/Use.html it seems however that this parameter is only relevant for onscreen display. I'll experiment with gmt directly and follow up.

[uliw]

Is there a way to keep the not yet converted ps-file, so I can try to run this via gmt call? I tried with setting pygmt.config(GMT_VERBOSE="d"), but it does remove the temp files.

ygmt-session [DEBUG]: GMT_Call_Command string: gmt psconvert -A -E50 -Fna_unified -Qg2 -Qt2 -Tf
pygmt-session [DEBUG]: Revised options: -A -E50 -Fna_unified -Qg2 -Qt2 -Tf
psconvert [DEBUG]: Ghostscript executable full name:
psconvert [DEBUG]: gmt_run_process_get_first_line: Pass to popen: [gs --version 2> /dev/null]
psconvert [DEBUG]: gs --version 2> /dev/null was successful
psconvert [DEBUG]: Ghostscript version: 10.07.0
psconvert [DEBUG]: Use PS filename /home/uliw/.gmt/sessions/gmt_session.66625/gmt_1.ps-
psconvert [DEBUG]: Hidden PS file /home/uliw/.gmt/sessions/gmt_session.66625/gmt_1.ps- found
psconvert [DEBUG]: Complete partial PS file /home/uliw/.gmt/sessions/gmt_session.66625/gmt_1.ps-
psconvert [DEBUG]: Size of half-baked PS file = 4226838795.
psconvert [DEBUG]: Fattened up PS file /home/uliw/.gmt/sessions/gmt_session.66625/gmt_1.ps-
psconvert [INFORMATION]: Processing /home/uliw/.gmt/sessions/gmt_session.66625/gmt_1.ps-...
psconvert [INFORMATION]: Find HiResBoundingBox ...
psconvert [DEBUG]: Running: gs -q -dNOSAFER -dNOPAUSE -dBATCH -sDEVICE=bbox -DPSL_no_pagefill -dMaxBitmap=2147483647 -dUseFastColor=true '/home/uliw/.gmt/sessions/gmt_session.66625/gmt_1.ps-' 2> '/home/uliw/.gmt/sessions/gmt_session.66625/psconvert_66625c.bb'
Error: /limitcheck in /----nostringval----
Operand stack:

Execution stack:
   %interp_exit   .runexec2   --nostringval--   --nostringval--   --nostringval--   2   %stopped_push   --nostringval--   --nostringval--   --nostringval--   false   1   %stopped_push   1804   1   3   %oparray_pop   1803   1   3   %oparray_pop   1788   1   3   %oparray_pop   1659   1   3   %oparray_pop   --nostringval--   %errorexec_pop   .runexec2   --nostringval--   --nostringval--   --nostringval--   2   %stopped_push
Dictionary stack:
   --dict:749/1123(ro)(G)--   --dict:0/20(G)--   --dict:85/200(L)--   --dict:157/250(L)--
Current allocation mode is local
Last OS error: No such file or directory
psconvert [ERROR]: System call [gs -q -dNOSAFER -dNOPAUSE -dBATCH -sDEVICE=bbox -DPSL_no_pagefill -dMaxBitmap=2147483647 -dUseFastColor=true '/home/uliw/.gmt/sessions/gmt_session.66625/gmt_1.ps-' 2> '/home/uliw/.gmt/sessions/gmt_session.66625/psconvert_66625c.bb'] returned error 256.
psconvert [DEBUG]: Delete /home/uliw/.gmt/sessions/gmt_session.66625/psconvert_66625c.bb
Traceback (most recent call last):
  File "/home/uliw/user/n_america/na_unified.py", line 134, in <module>
    fig.savefig("na_unified.pdf", dpi=50,
    ~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^
                # resize="+m2c",
                ^^^^^^^^^^^^^^^^
                # gs_option="-dMaxBitmap=20000000000, -dMaxMemory=2000000000",
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                ) # Limit ghostscript memory)
                ^
  File "/home/uliw/miniforge3/envs/py314/lib/python3.14/site-packages/pygmt/figure.py", line 254, in savefig
    self.psconvert(prefix=prefix, fmt=fmts[ext], crop=crop, **kwargs)
    ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/uliw/miniforge3/envs/py314/lib/python3.14/site-packages/pygmt/helpers/decorators.py", line 591, in new_module
    return module_func(*args, **kwargs)
  File "/home/uliw/miniforge3/envs/py314/lib/python3.14/site-packages/pygmt/src/psconvert.py", line 146, in psconvert
    lib.call_module(module="psconvert", args=build_arg_list(aliasdict))
    ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/uliw/miniforge3/envs/py314/lib/python3.14/site-packages/pygmt/clib/session.py", line 671, in call_module
    raise GMTCLibError(msg)
pygmt.exceptions.GMTCLibError: Module 'psconvert' failed with status code 79:
psconvert [ERROR]: System call [gs -q -dNOSAFER -dNOPAUSE -dBATCH -sDEVICE=bbox -DPSL_no_pagefill -dMaxBitmap=2147483647 -dUseFastColor=true '/home/uliw/.gmt/sessions/gmt_session.66625/gmt_1.ps-' 2> '/home/uliw/.gmt/sessions/gmt_session.66625/psconvert_66625c.bb'] returned error 256.
pygmt-session [DEBUG]: gmtinit_parse_map_annot_oblique: Converted separate,lon_horizontal,lat_horizontal,tick_extend to 14
pygmt-session [DEBUG]: The PROJ_GEODESIC set to Vincenty
pygmt-session [DEBUG]: Exit:  gmt_reload_settings
pygmt-session [DEBUG]: Enter: gmtlib_plot_C_format
pygmt-session [DEBUG]: Exit:  gmtlib_plot_C_format
pygmt-session [DEBUG]: Enter: gmtinit_get_history
pygmt-session [DEBUG]: gmtlib_get_graphics_item: Fig: 1 Subplot: 2 Panel: () Inset: 0
pygmt-session [DEBUG]: Enter: gmt_hash_init
pygmt-session [DEBUG]: Exit:  gmt_hash_init
pygmt-session [DEBUG]: Exit:  gmtinit_get_history
pygmt-session [DEBUG]: Initialize FFTW with 32 threads.
pygmt-session [DEBUG]: GMT_Create_Session initialized GMT structure
pygmt-session [DEBUG]: Shared Library # 0 (core). Path = /home/uliw/miniforge3/envs/py314/lib/libgmt.so
pygmt-session [DEBUG]: Loading GMT plugins from: /home/uliw/miniforge3/envs/py314/lib/gmt/plugins
pygmt-session [DEBUG]: Shared Library # 1 (supplements). Path = /home/uliw/miniforge3/envs/py314/lib/gmt/plugins/supplements.so
pygmt-session [DEBUG]: GMT now running in modern mode [Session ID = 66625]
pygmt-session [DEBUG]: GMT_Call_Command string: gmt end (null)
pygmt-session [DEBUG]: Revised options: (null)
[Session pygmt-session (29)]: Error returned from GMT API: GMT_ARG_IS_NULL (4)
end [DEBUG]: End Workflow.  Session ID = 66625. Directory /home/uliw/.gmt/sessions/gmt_session.66625 removed.
end [DEBUG]: Got session name as pygmt-session and default graphics formats as pdf
end [INFORMATION]: Process GMT figure queue: 2 figures found
end [INFORMATION]: Processing GMT figure #0 [pygmt-session pdf ]
end [INFORMATION]: Processing GMT figure GenericMappingTools/pygmt#1 [53d8375088584870b08da59151691f05 - ]
end [DEBUG]: GMT now running in modern mode [Session ID = 66625]
end [DEBUG]: GMT_Call_Command string: gmt figure 53d8375088584870b08da59151691f05
end [DEBUG]: Revised options: 53d8375088584870b08da59151691f05
end [DEBUG]: Enter: gmtinit_get_history
end [DEBUG]: gmtlib_get_graphics_item: Fig: 1 Subplot: 2 Panel: () Inset: 0
end [DEBUG]: Enter: gmt_hash_init
end [DEBUG]: Exit:  gmt_hash_init
end [DEBUG]: Exit:  gmtinit_get_history
end [INFORMATION]: Destroying the current workflow directory /home/uliw/.gmt/sessions/gmt_session.66625
end [DEBUG]: Delete gmt.1.cpt
end [DEBUG]: Delete gmt.1.legend
end [DEBUG]: Delete gmt.canvas.1
end [DEBUG]: Delete gmt.conf
end [DEBUG]: Delete gmt.conf.1
end [DEBUG]: Delete gmt.current
end [DEBUG]: Delete gmt.figures
end [DEBUG]: Delete gmt.frame.1
end [DEBUG]: Delete gmt.history
end [DEBUG]: Delete gmt.history.1
end [DEBUG]: Delete gmt.layers.1
end [DEBUG]: Delete gmt.session
end [DEBUG]: Delete gmt_1.ps-

[weiji14]

I am trying to generate a high res map in poster format

Ah, if that's the case... Have you set the dpi/-E parameter? E.g. for grdimage, it defaults to dpi=100, but you can increase that to 300 or 600. Also, psconvert has a dpi parameter, but you need to make sure your underlying map layers (especially the raster ones) are all high resolution before changing that.

[uliw]

I placed a breakpoint before calling psconvert to get access to the ps file. Using this GS immediately exits upon reading the file with a limitcheck. In my understanding, this is because some numbers in the ps file exceed the postscript specification. So this may have nothing todo with gmt/pygmt.

[seisman]

This is an upstream issue, so I'm transferring it to the upstream GMT repository.

To reproduce the issue in GMT CLI, try:

gmt psbasemap -R0/10/0/10 -JX10c -Baf > map.ps
gmt psconvert map.ps -C-dMaxBitmap=2000000 -S

The output is

gs -q -dNOPAUSE -dBATCH -dNOSAFER -dSCANCONVERTERTYPE=2 -dMaxBitmap=2000000 -dMaxBitmap=2147483647 -dUseFastColor=true -dGraphicsAlphaBits=2 -dTextAlphaBits=4 -sDEVICE=jpeg -dJPEGQ=90 -g2480x3509 -r300 -sOutputFile='map.jpg' './psconvert_3324091d.eps'

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