#!/usr/bin/env python3

GPIB_ADDR = 18   # change to suit your instrument

import pyvisa, hpgl, sys, io, os
from contextlib import contextmanager
@contextmanager
def _no_stderr():
  orig_stderr=os.dup(2); dev_null=os.open(os.devnull, os.O_WRONLY)
  os.dup2(dev_null, 2); os.close(dev_null); yield
  os.dup2(orig_stderr, 2); os.close(orig_stderr)

rm=pyvisa.ResourceManager()
instr=rm.open_resource('GPIB0::'+str(GPIB_ADDR)+'::INSTR')
bus=rm.open_resource("GPIB0::INTFC")

# Get the HPGL data
with _no_stderr():
  instr.write("PLOT")
  bus.send_command(bytes([0x3f, 0x20, 0x5f, 0x40+GPIB_ADDR]))
  hpgl_data=bus.visalib.buffer_read(bus.session,32000)

# Fix the HPGL fonts
hpgl_data=hpgl_data[0].replace(b';SR1.67,1.78;', b';SR0.1,0.1;')

# Convert to SVG and fix linewidth
svg_data=hpgl.hpgl2svg(io.StringIO(hpgl_data.decode("utf-8")))
svg_data=svg_data.replace('stroke-width="14.000"', 'stroke-width="1.500"')

print("Content-type: image/svg+xml\n\n"+svg_data)