aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/python/Pillow/py2/PIL/GimpGradientFile.py
blob: f48e7f76ef347ab4ba7ba64313b175f839d2b417 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
#
# Python Imaging Library
# $Id$
#
# stuff to read (and render) GIMP gradient files
#
# History:
#       97-08-23 fl     Created
#
# Copyright (c) Secret Labs AB 1997.
# Copyright (c) Fredrik Lundh 1997.
#
# See the README file for information on usage and redistribution.
#

from math import log, pi, sin, sqrt

from ._binary import o8

# --------------------------------------------------------------------
# Stuff to translate curve segments to palette values (derived from
# the corresponding code in GIMP, written by Federico Mena Quintero.
# See the GIMP distribution for more information.)
#

EPSILON = 1e-10


def linear(middle, pos):
    if pos <= middle:
        if middle < EPSILON:
            return 0.0
        else:
            return 0.5 * pos / middle
    else:
        pos = pos - middle
        middle = 1.0 - middle
        if middle < EPSILON:
            return 1.0
        else:
            return 0.5 + 0.5 * pos / middle


def curved(middle, pos):
    return pos ** (log(0.5) / log(max(middle, EPSILON)))


def sine(middle, pos):
    return (sin((-pi / 2.0) + pi * linear(middle, pos)) + 1.0) / 2.0


def sphere_increasing(middle, pos):
    return sqrt(1.0 - (linear(middle, pos) - 1.0) ** 2)


def sphere_decreasing(middle, pos):
    return 1.0 - sqrt(1.0 - linear(middle, pos) ** 2)


SEGMENTS = [linear, curved, sine, sphere_increasing, sphere_decreasing]


class GradientFile(object):

    gradient = None

    def getpalette(self, entries=256):

        palette = []

        ix = 0
        x0, x1, xm, rgb0, rgb1, segment = self.gradient[ix]

        for i in range(entries):

            x = i / float(entries - 1)

            while x1 < x:
                ix += 1
                x0, x1, xm, rgb0, rgb1, segment = self.gradient[ix]

            w = x1 - x0

            if w < EPSILON:
                scale = segment(0.5, 0.5)
            else:
                scale = segment((xm - x0) / w, (x - x0) / w)

            # expand to RGBA
            r = o8(int(255 * ((rgb1[0] - rgb0[0]) * scale + rgb0[0]) + 0.5))
            g = o8(int(255 * ((rgb1[1] - rgb0[1]) * scale + rgb0[1]) + 0.5))
            b = o8(int(255 * ((rgb1[2] - rgb0[2]) * scale + rgb0[2]) + 0.5))
            a = o8(int(255 * ((rgb1[3] - rgb0[3]) * scale + rgb0[3]) + 0.5))

            # add to palette
            palette.append(r + g + b + a)

        return b"".join(palette), "RGBA"


##
# File handler for GIMP's gradient format.


class GimpGradientFile(GradientFile):
    def __init__(self, fp):

        if fp.readline()[:13] != b"GIMP Gradient":
            raise SyntaxError("not a GIMP gradient file")

        line = fp.readline()

        # GIMP 1.2 gradient files don't contain a name, but GIMP 1.3 files do
        if line.startswith(b"Name: "):
            line = fp.readline().strip()

        count = int(line)

        gradient = []

        for i in range(count):

            s = fp.readline().split()
            w = [float(x) for x in s[:11]]

            x0, x1 = w[0], w[2]
            xm = w[1]
            rgb0 = w[3:7]
            rgb1 = w[7:11]

            segment = SEGMENTS[int(s[11])]
            cspace = int(s[12])

            if cspace != 0:
                raise IOError("cannot handle HSV colour space")

            gradient.append((x0, x1, xm, rgb0, rgb1, segment))

        self.gradient = gradient