An extremely hacky bit of code to split an SVG of joined line paths into individual lines, and merge straight lines made of smaller lines into single lines

split_svg_paths.py

# An extremely hacky bit of code that takes SVG files output by Blender
# and splits all the multi-node line paths into single line paths to make
# editing easier. Example: A right-angle path is now two lines that meet.
#
# Blender has a habit of outputting really _weird_ paths that are annoying
# to edit on geometric shapes, and also outputs straight lines that are
# made up of many smaller straight line nodes. This code also merges those
# mini-line lines into single lines to stop you throwing your computer out
# of the window when you try and work with the SVG.
#
# The SVG parsing in this is hilarious and lazy because I only ever needed
# to use this once. It will likely not work with SVG output from any other
# program, or even different types of SVG from Blender - but just in case
# here's the code. I couldn't find anyone else doing this.

import sys
import re
import math

with open(sys.argv[1]) as f:
    for line in f.readlines():
        line = line.strip()
        matches = re.search('(\s*<path d=" M )([^"]+)( ".*)$', line)
        if matches:
            tail = matches.group(3)
            tail = tail.replace('stroke-width="3.0"', 'stroke-width="1.0"')

            lines = []

            # Split into individual lines
            coords = re.findall('(\d+\.\d+, \d+.\d+)', matches.group(2))
            last_coord = coords.pop(0)
            for coord in coords:
                lines.append((last_coord, coord))
                last_coord = coord

            # Merge lines that are part of a contiguous line
            merged_lines = []

            last_line = lines.pop(0)
            last_point = last_line[0]
            for line in lines:
                # Last segment
                x1, y1 = last_line[0].split(", ")
                x2, y2 = last_line[1].split(", ")
                last_slope = math.atan2(float(x2) - float(x1), float(y2) - float(y1))
                
                # This segment
                x1, y1 = line[0].split(", ")
                x2, y2 = line[1].split(", ")
                this_slope = math.atan2(float(x2) - float(x1), float(y2) - float(y1))

                if abs(last_slope - this_slope) > 0.01:
                    merged_lines.append((last_point, last_line[1]))
                    last_point = line[0]

                last_line = line

            merged_lines.append((last_point, last_line[1]))

            for line in merged_lines:
                print("%s%s %s%s" % (matches.group(1), line[0], line[1], tail))
        else:
            print(line)