# Sketch - A Python-based interactive drawing program
# Copyright (C) 1997, 1998 by Bernhard Herzog
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Library General Public
# License as published by the Free Software Foundation; either
# version 2 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Library General Public License for more details.
#
# You should have received a copy of the GNU Library General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
#
# color gradient classes
#
from blend import Blend,MismatchError
class Gradient:
def __init__(self, duplicate = None):
pass
def ColorAt(self, pos):
pass
def Duplicate(self):
return self.__class__(duplicate = self)
class MultiGradient(Gradient):
def __init__(self, colors = (), duplicate = None):
if duplicate is not None:
self.colors = duplicate.colors[:]
else:
if len(colors) < 2:
raise ValueError, 'at least 2 colors required'
self.colors = colors
def StartColor(self):
return self.colors[0][-1]
def SetStartColor(self, color):
undo = (self.SetStartColor, self.colors[0][-1])
self.colors[0] = (0, color)
return undo
def EndColor(self):
return self.colors[-1][-1]
def SetEndColor(self, color):
undo = (self.SetEndColor, self.colors[-1][-1])
self.colors[-1] = (1, color)
return undo
def ColorAt(self, pos):
colors = self.colors
for i in range(len(colors) - 1):
if colors[i][0] <= pos and colors[i + 1][0] >= pos:
break
else:
return self.EndColor()
start_pos, start_color = colors[i]
if i < len(colors) - 1:
end_pos, end_color = colors[i + 1]
else:
return start_color
return Blend(end_color, start_color,
(pos - start_pos) / float(end_pos - start_pos))
def Sample(self, num):
colors = self.colors
max = num - 1.0
pos1, color1 = colors[0]
pos2, color2 = colors[1]
diff = float(pos2 - pos1)
cur = 1
result = []
blend = color1.Blend
for i in range(num):
frac = i / max
while frac > pos2:
pos1 = pos2; color1 = color2
cur = cur + 1
pos2, color2 = colors[cur]
diff = float(pos2 - pos1)
blend = color1.Blend
frac = (frac - pos1) / diff
result.append(blend(color2, 1 - frac, frac))
return result
def Colors(self):
return self.colors
def SetColors(self):
undo = (self.SetColors, self.colors)
self.colors = colors
return undo
def Blend(self, other, frac1, frac2):
if type(other) == type(self.colors[0][-1]):
# blend a gradient with a single color
sc = self.colors
c = []
for i in range(len(sc)):
p1, c1 = sc[i]
c.append((p1, c1.Blend(other, frac1, frac2)))
return self.__class__(c)
elif other.__class__ == self.__class__:
# blend two MultiGradient instances
# XXX: improve this...
length = min(len(self.colors), len(other.colors))
sc = self.colors[:length - 1]
sc.append(self.colors[-1])
oc = other.colors[:length - 1]
oc.append(other.colors[-1])
c = []
for i in range(length):
p1, c1 = sc[i]
p2, c2 = oc[i]
c.append((frac1 * p1 + frac2 * p2,
Blend(c1, c2, frac1, frac2)))
return self.__class__(c)
else:
raise MismatchError
def SaveToFile(self, file):
file.Gradient(self.colors)
# convenience function for the most common gradient type
def CreateSimpleGradient(start, end):
return MultiGradient([(0, start), (1, end)])
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