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#!/usr/bin/env python
import ast
import operator as op
import inkex
OPS = {ast.Add: op.add,
ast.Sub: op.sub,
ast.Mult: op.mul,
ast.Div: op.truediv,
ast.Pow: op.pow,
ast.BitXor: op.xor,
ast.USub: op.neg}
def eval_expr(expr, namespace):
"""
>>> eval_expr('2^6')
4
>>> eval_expr('2**6')
64
>>> eval_expr('1 + 2*3**(4^5) / (6 + -7)')
-5.0
"""
return _eval(ast.parse(expr, mode='eval').body, namespace)
def _eval(node, namespace):
if isinstance(node, ast.Num): # <number>
return node.n
elif isinstance(node, ast.Name): # <variable> (must be in namespace)
return namespace[node.id]
elif isinstance(node, ast.BinOp): # <left> <operator> <right>
return OPS[type(node.op)](_eval(node.left, namespace), _eval(node.right, namespace))
elif isinstance(node, ast.UnaryOp): # <operator> <operand> e.g., -1
return OPS[type(node.op)](_eval(node.operand, namespace))
else:
raise TypeError(node)
class Custom(inkex.ColorExtension):
"""Custom colour functions per channel"""
def add_arguments(self, pars):
pars.add_argument("--tab")
pars.add_argument("-r", "--r", default="r", help="red channel function")
pars.add_argument("-g", "--g", default="g", help="green channel function")
pars.add_argument("-b", "--b", default="b", help="blue channel function")
pars.add_argument("-s", "--scale", type=float, default=1.0, help="The input (r,g,b) range")
def modify_color(self, name, color):
opt = self.options
factor = 255.0 / opt.scale
# add stuff to be accessible from within the custom color function here.
namespace = {
'r': float(color.red) / factor,
'g': float(color.green) / factor,
'b': float(color.blue) / factor}
color.red = int(eval_expr(opt.r.strip(), namespace) * factor)
color.green = int(eval_expr(opt.g.strip(), namespace) * factor)
color.blue = int(eval_expr(opt.b.strip(), namespace) * factor)
return color
if __name__ == '__main__':
Custom().run()
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