io_curve_svg/svg_util.py

   1 # SPDX-License-Identifier: GPL-2.0-or-later
   2
   3 import re
   4
   5
   6 units = {"": 1.0,
   7          "px": 1.0,
   8          "in": 90.0,
   9          "mm": 90.0 / 25.4,
  10          "cm": 90.0 / 2.54,
  11          "pt": 1.25,
  12          "pc": 15.0,
  13          "em": 1.0,
  14          "ex": 1.0,
  15          "INVALID": 1.0,  # some DocBook files contain this
  16          }
  17
  18
  19 def srgb_to_linearrgb(c):
  20     if c < 0.04045:
  21         return 0.0 if c < 0.0 else c * (1.0 / 12.92)
  22     else:
  23         return pow((c + 0.055) * (1.0 / 1.055), 2.4)
  24
  25
  26 def check_points_equal(point_a, point_b):
  27     return (abs(point_a[0] - point_b[0]) < 1e-6 and
  28             abs(point_a[1] - point_b[1]) < 1e-6)
  29
  30 match_number = r"-?\d+(\.\d+)?([eE][-+]?\d+)?"
  31 match_first_comma = r"^\s*(?=,)"
  32 match_comma_pair = r",\s*(?=,)"
  33 match_last_comma = r",\s*$"
  34
  35 match_number_optional_parts = r"(-?\d+(\.\d*)?([eE][-+]?\d+)?)|(-?\.\d+([eE][-+]?\d+)?)"
  36 re_match_number_optional_parts = re.compile(match_number_optional_parts)
  37
  38 array_of_floats_pattern = f"({match_number_optional_parts})|{match_first_comma}|{match_comma_pair}|{match_last_comma}"
  39 re_array_of_floats_pattern = re.compile(array_of_floats_pattern)
  40
  41 def parse_array_of_floats(text):
  42     """
  43     Accepts comma or space separated list of floats (without units) and returns an array
  44     of floating point values.
  45     """
  46     elements = re_array_of_floats_pattern.findall(text)
  47     return [value_to_float(v[0]) for v in elements]
  48
  49
  50 def read_float(text: str, start_index: int = 0):
  51     """
  52     Reads floating point value from a string. Parsing starts at the given index.
  53
  54     Returns the value itself (as a string) and index of first character after the value.
  55     """
  56
  57     n = len(text)
  58
  59     # Skip leading whitespace characters and characters which we consider ignorable for float
  60     # (like values separator).
  61     while start_index < n and (text[start_index].isspace() or text[start_index] == ','):
  62         start_index += 1
  63     if start_index == n:
  64         return "0", start_index
  65
  66     text_part = text[start_index:]
  67     match = re_match_number_optional_parts.match(text_part)
  68
  69     if match is None:
  70         raise Exception('Invalid float value near ' + text[start_index:start_index + 10])
  71
  72     token = match.group(0)
  73     endptr = start_index + match.end(0)
  74
  75     return token, endptr
  76
  77
  78 def parse_coord(coord, size):
  79     """
  80     Parse coordinate component to common basis
  81
  82     Needed to handle coordinates set in cm, mm, inches.
  83     """
  84
  85     token, last_char = read_float(coord)
  86     val = float(token)
  87     unit = coord[last_char:].strip()  # strip() in case there is a space
  88
  89     if unit == '%':
  90         return float(size) / 100.0 * val
  91     else:
  92         return val * units[unit]
  93
  94     return val
  95
  96
  97 def value_to_float(value_encoded: str):
  98     """
  99     A simple wrapper around float() which supports empty strings (which are converted to 0).
 100     """
 101     if len(value_encoded) == 0:
 102         return 0
 103     return float(value_encoded)