codekingpro/portable-devtools

1#
2# Python Imaging Library
3# $Id$
4#
5# stuff to read (and render) GIMP gradient files
6#
7# History:
8#       97-08-23 fl     Created
9#
10# Copyright (c) Secret Labs AB 1997.
11# Copyright (c) Fredrik Lundh 1997.
12#
13# See the README file for information on usage and redistribution.
14#
15
16"""
17Stuff to translate curve segments to palette values (derived from
18the corresponding code in GIMP, written by Federico Mena Quintero.
19See the GIMP distribution for more information.)
20"""
21
22from __future__ import annotations
23
24from math import log, pi, sin, sqrt
25
26from ._binary import o8
27
28TYPE_CHECKING = False
29if TYPE_CHECKING:
30    from collections.abc import Callable
31    from typing import IO
32
33EPSILON = 1e-10
34""""""  # Enable auto-doc for data member
35
36
37def linear(middle: float, pos: float) -> float:
38    if pos <= middle:
39        if middle < EPSILON:
40            return 0.0
41        else:
42            return 0.5 * pos / middle
43    else:
44        pos = pos - middle
45        middle = 1.0 - middle
46        if middle < EPSILON:
47            return 1.0
48        else:
49            return 0.5 + 0.5 * pos / middle
50
51
52def curved(middle: float, pos: float) -> float:
53    return pos ** (log(0.5) / log(max(middle, EPSILON)))
54
55
56def sine(middle: float, pos: float) -> float:
57    return (sin((-pi / 2.0) + pi * linear(middle, pos)) + 1.0) / 2.0
58
59
60def sphere_increasing(middle: float, pos: float) -> float:
61    return sqrt(1.0 - (linear(middle, pos) - 1.0) ** 2)
62
63
64def sphere_decreasing(middle: float, pos: float) -> float:
65    return 1.0 - sqrt(1.0 - linear(middle, pos) ** 2)
66
67
68SEGMENTS = [linear, curved, sine, sphere_increasing, sphere_decreasing]
69""""""  # Enable auto-doc for data member
70
71
72class GradientFile:
73    gradient: (
74        list[
75            tuple[
76                float,
77                float,
78                float,
79                list[float],
80                list[float],
81                Callable[[float, float], float],
82            ]
83        ]
84        | None
85    ) = None
86
87    def getpalette(self, entries: int = 256) -> tuple[bytes, str]:
88        assert self.gradient is not None
89        palette = []
90
91        ix = 0
92        x0, x1, xm, rgb0, rgb1, segment = self.gradient[ix]
93
94        for i in range(entries):
95            x = i / (entries - 1)
96
97            while x1 < x:
98                ix += 1
99                x0, x1, xm, rgb0, rgb1, segment = self.gradient[ix]
100
101            w = x1 - x0
102
103            if w < EPSILON:
104                scale = segment(0.5, 0.5)
105            else:
106                scale = segment((xm - x0) / w, (x - x0) / w)
107
108            # expand to RGBA
109            r = o8(int(255 * ((rgb1[0] - rgb0[0]) * scale + rgb0[0]) + 0.5))
110            g = o8(int(255 * ((rgb1[1] - rgb0[1]) * scale + rgb0[1]) + 0.5))
111            b = o8(int(255 * ((rgb1[2] - rgb0[2]) * scale + rgb0[2]) + 0.5))
112            a = o8(int(255 * ((rgb1[3] - rgb0[3]) * scale + rgb0[3]) + 0.5))
113
114            # add to palette
115            palette.append(r + g + b + a)
116
117        return b"".join(palette), "RGBA"
118
119
120class GimpGradientFile(GradientFile):
121    """File handler for GIMP's gradient format."""
122
123    def __init__(self, fp: IO[bytes]) -> None:
124        if not fp.readline().startswith(b"GIMP Gradient"):
125            msg = "not a GIMP gradient file"
126            raise SyntaxError(msg)
127
128        line = fp.readline()
129
130        # GIMP 1.2 gradient files don't contain a name, but GIMP 1.3 files do
131        if line.startswith(b"Name: "):
132            line = fp.readline().strip()
133
134        count = int(line)
135
136        self.gradient = []
137
138        for i in range(count):
139            s = fp.readline().split()
140            w = [float(x) for x in s[:11]]
141
142            x0, x1 = w[0], w[2]
143            xm = w[1]
144            rgb0 = w[3:7]
145            rgb1 = w[7:11]
146
147            segment = SEGMENTS[int(s[11])]
148            cspace = int(s[12])
149
150            if cspace != 0:
151                msg = "cannot handle HSV colour space"
152                raise OSError(msg)
153
154            self.gradient.append((x0, x1, xm, rgb0, rgb1, segment))
155