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#
# 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.
#
"""
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.)
"""
from math import log, pi, sin, sqrt
from ._binary import o8
EPSILON = 1e-10
"""""" # Enable auto-doc for data member
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]
"""""" # Enable auto-doc for data member
class GradientFile:
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 / (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"
class GimpGradientFile(GradientFile):
"""File handler for GIMP's gradient format."""
def __init__(self, fp):
if fp.readline()[:13] != b"GIMP Gradient":
msg = "not a GIMP gradient file"
raise SyntaxError(msg)
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:
msg = "cannot handle HSV colour space"
raise OSError(msg)
gradient.append((x0, x1, xm, rgb0, rgb1, segment))
self.gradient = gradient
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