def set_transfer_function(self, colors=None, opacities=None):
""" Update the volume mapper's transfer function.
"""
lerp = lambda x: self.vmin + x * (self.vmax - self.vmin) # noqa
if colors is not None:
self.colors = colors
if opacities is not None:
self.opacities = opacities
color_tf = tvtk.ColorTransferFunction()
for color in self.colors.values():
color_tf.add_rgb_point(lerp(color[0]), *(color[1:]))
opacity_tf = tvtk.PiecewiseFunction()
alphas = self.opacities.values()
for i, alpha in enumerate(alphas):
x = alpha[0]
if i > 0:
# Look back one item. VTK doesn't like exact vertical jumps, so
# we need to jog a value that is exactly equal by a little bit.
if alphas[i-1][0] == alpha[0]:
x += 1e-8
opacity_tf.add_point(lerp(x), alpha[1] * self.global_alpha)
self._set_volume_ctf(color_tf, opacity_tf)
def __init__(self, num_entries):
self.size = num_entries
self.table = tvtk.ColorTransferFunction()
try:
self.table.range = (0.0, 1.0)
except Exception:
# VTK versions < 5.2 don't seem to need this.
pass
self.alpha = tvtk.PiecewiseFunction()
# These VTK classes perform the interpolation for us.
# insert the control points for the left and the right end of the
# gradient. These are fixed (i.e. cannot be moved or deleted) and
# allow one to set begin and end colors.
left_control_point = ColorControlPoint(fixed=True,
active_channels="hsva")
left_control_point.set_pos(0.0)
left_control_point.color.set_rgb(0.0, 0.0, 0.0)
right_control_point = ColorControlPoint(fixed=True,
active_channels="hsva")
right_control_point.set_pos(1.0)
right_control_point.color.set_rgb(1.0, 1.0, 1.0)
self.control_points = [left_control_point, right_control_point]
# note: The array of control points always has to be sorted by gradient
# position of the control points.
# insert another control point. This one has no real function, it
# is just there to make the gradient editor more colorful initially
# and suggest to the (first time user) that it is actually possible to
# place more control points.
mid_control_point = ColorControlPoint(active_channels="hsv")
mid_control_point.set_pos(0.4)
mid_control_point.color.set_rgb(1.0, 0.4, 0.0)
self.insert_control_point(mid_control_point)
# These variables are only for compatibility with GradientTableOld.
self.scaling_function_string = "" # will receive the function string if
# set, e.g. "x**(4*a)"
self.scaling_function_parameter = 0.5 # the parameter a, slider controlled
self.scaling_function = None # the actual function object. takes one
# position parameter. None if disabled.
self.update()