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import math
from traits.api import Float, Property, List, Str, Range
from enable.api import Component
from kiva.trait_defs.kiva_font_trait import KivaFont
from kiva import affine
def percent_to_db(percent):
if percent == 0.0:
db = float('-inf')
else:
db = 20 * math.log10(percent / 100.0)
return db
def db_to_percent(db):
percent = math.pow(10, db / 20.0 + 2)
return percent
class VUMeter(Component):
# Value expressed in dB
db = Property(Float)
# Value expressed as a percent.
percent = Range(low=0.0)
# The maximum value to be display in the VU Meter, expressed as a percent.
max_percent = Float(150.0)
# Angle (in degrees) from a horizontal line through the hinge of the
# needle to the edge of the meter axis.
angle = Float(45.0)
# Values of the percentage-based ticks; these are drawn and labeled along
# the bottom of the curve axis.
percent_ticks = List(range(0, 101, 20))
# Text to write in the middle of the VU Meter.
text = Str("VU")
# Font used to draw `text`.
text_font = KivaFont("modern 48")
# Font for the db tick labels.
db_tick_font = KivaFont("modern 16")
# Font for the percent tick labels.
percent_tick_font = KivaFont("modern 12")
# beta is the fraction of the of needle that is "hidden".
# beta == 0 puts the hinge point of the needle on the bottom
# edge of the window. Values that result in a decent looking
# meter are 0 < beta < .65.
# XXX needs a better name!
_beta = Float(0.3)
# _outer_radial_margin is the radial extent beyond the circular axis
# to include in calculations of the space required for the meter.
# This allows room for the ticks and labels.
_outer_radial_margin = Float(60.0)
# The angle (in radians) of the span of the curve axis.
_phi = Property(Float, depends_on=['angle'])
# This is the radius of the circular axis (in screen coordinates).
_axis_radius = Property(Float, depends_on=['_phi', 'width', 'height'])
#---------------------------------------------------------------------
# Trait Property methods
#---------------------------------------------------------------------
def _get_db(self):
db = percent_to_db(self.percent)
return db
def _set_db(self, value):
self.percent = db_to_percent(value)
def _get__phi(self):
phi = math.pi * (180.0 - 2 * self.angle) / 180.0
return phi
def _get__axis_radius(self):
M = self._outer_radial_margin
beta = self._beta
w = self.width
h = self.height
phi = self._phi
R1 = w / (2 * math.sin(phi / 2)) - M
R2 = (h - M) / (1 - beta * math.cos(phi / 2))
R = min(R1, R2)
return R
#---------------------------------------------------------------------
# Trait change handlers
#---------------------------------------------------------------------
def _anytrait_changed(self):
self.request_redraw()
#---------------------------------------------------------------------
# Component API
#---------------------------------------------------------------------
def _draw_mainlayer(self, gc, view_bounds=None, mode="default"):
beta = self._beta
phi = self._phi
w = self.width
M = self._outer_radial_margin
R = self._axis_radius
# (ox, oy) is the position of the "hinge point" of the needle
# (i.e. the center of rotation). For beta > ~0, oy is negative,
# so this point is below the visible region.
ox = self.x + self.width // 2
oy = -beta * R * math.cos(phi / 2) + 1
left_theta = math.radians(180 - self.angle)
right_theta = math.radians(self.angle)
# The angle of the 100% position.
nominal_theta = self._percent_to_theta(100.0)
# The color of the axis for percent > 100.
red = (0.8, 0, 0)
with gc:
gc.set_antialias(True)
# Draw everything relative to the center of the circles.
gc.translate_ctm(ox, oy)
# Draw the primary ticks and tick labels on the curved axis.
gc.set_fill_color((0, 0, 0))
gc.set_font(self.db_tick_font)
for db in [-20, -10, -7, -5, -3, -2, -1, 0, 1, 2, 3]:
db_percent = db_to_percent(db)
theta = self._percent_to_theta(db_percent)
x1 = R * math.cos(theta)
y1 = R * math.sin(theta)
x2 = (R + 0.3 * M) * math.cos(theta)
y2 = (R + 0.3 * M) * math.sin(theta)
gc.set_line_width(2.5)
gc.move_to(x1, y1)
gc.line_to(x2, y2)
gc.stroke_path()
text = str(db)
if db > 0:
text = '+' + text
self._draw_rotated_label(gc, text, theta, R + 0.4 * M)
# Draw the secondary ticks on the curve axis.
for db in [-15, -9, -8, -6, -4, -0.5, 0.5]:
##db_percent = 100 * math.pow(10.0, db / 20.0)
db_percent = db_to_percent(db)
theta = self._percent_to_theta(db_percent)
x1 = R * math.cos(theta)
y1 = R * math.sin(theta)
x2 = (R + 0.2 * M) * math.cos(theta)
y2 = (R + 0.2 * M) * math.sin(theta)
gc.set_line_width(1.0)
gc.move_to(x1, y1)
gc.line_to(x2, y2)
gc.stroke_path()
# Draw the percent ticks and label on the bottom of the
# curved axis.
gc.set_font(self.percent_tick_font)
gc.set_fill_color((0.5, 0.5, 0.5))
gc.set_stroke_color((0.5, 0.5, 0.5))
percents = self.percent_ticks
for tick_percent in percents:
theta = self._percent_to_theta(tick_percent)
x1 = (R - 0.15 * M) * math.cos(theta)
y1 = (R - 0.15 * M) * math.sin(theta)
x2 = R * math.cos(theta)
y2 = R * math.sin(theta)
gc.set_line_width(2.0)
gc.move_to(x1, y1)
gc.line_to(x2, y2)
gc.stroke_path()
text = str(tick_percent)
if tick_percent == percents[-1]:
text = text + "%"
self._draw_rotated_label(gc, text, theta, R - 0.3 * M)
if self.text:
gc.set_font(self.text_font)
tx, ty, tw, th = gc.get_text_extent(self.text)
gc.set_fill_color((0, 0, 0, 0.25))
gc.set_text_matrix(affine.affine_from_rotation(0))
gc.set_text_position(-0.5 * tw,
(0.75 * beta + 0.25) * R)
gc.show_text(self.text)
# Draw the red curved axis.
gc.set_stroke_color(red)
w = 10
gc.set_line_width(w)
gc.arc(0, 0, R + 0.5 * w - 1, right_theta, nominal_theta)
gc.stroke_path()
# Draw the black curved axis.
w = 4
gc.set_line_width(w)
gc.set_stroke_color((0, 0, 0))
gc.arc(0, 0, R + 0.5 * w - 1, nominal_theta, left_theta)
gc.stroke_path()
# Draw the filled arc at the bottom.
gc.set_line_width(2)
gc.set_stroke_color((0, 0, 0))
gc.arc(0, 0, beta * R, math.radians(self.angle),
math.radians(180 - self.angle))
gc.stroke_path()
gc.set_fill_color((0, 0, 0, 0.25))
gc.arc(0, 0, beta * R, math.radians(self.angle),
math.radians(180 - self.angle))
gc.fill_path()
# Draw the needle.
percent = self.percent
# If percent exceeds max_percent, the needle is drawn at max_percent.
if percent > self.max_percent:
percent = self.max_percent
needle_theta = self._percent_to_theta(percent)
gc.rotate_ctm(needle_theta - 0.5 * math.pi)
self._draw_vertical_needle(gc)
#---------------------------------------------------------------------
# Private methods
#---------------------------------------------------------------------
def _draw_vertical_needle(self, gc):
""" Draw the needle of the meter, pointing straight up. """
beta = self._beta
R = self._axis_radius
end_y = beta * R
blob_y = R - 0.6 * self._outer_radial_margin
tip_y = R + 0.2 * self._outer_radial_margin
lw = 5
with gc:
gc.set_alpha(1)
gc.set_fill_color((0, 0, 0))
# Draw the needle from the bottom to the blob.
gc.set_line_width(lw)
gc.move_to(0, end_y)
gc.line_to(0, blob_y)
gc.stroke_path()
# Draw the thin part of the needle from the blob to the tip.
gc.move_to(lw, blob_y)
control_y = blob_y + 0.25 * (tip_y - blob_y)
gc.quad_curve_to( 0.2 * lw, control_y, 0, tip_y)
gc.quad_curve_to(-0.2 * lw, control_y, -lw, blob_y)
gc.line_to(lw, blob_y)
gc.fill_path()
# Draw the blob on the needle.
gc.arc(0, blob_y, 6.0, 0, 2 * math.pi)
gc.fill_path()
def _draw_rotated_label(self, gc, text, theta, radius):
tx, ty, tw, th = gc.get_text_extent(text)
rr = math.sqrt(radius ** 2 + (0.5 * tw) ** 2)
dtheta = math.atan2(0.5 * tw, radius)
text_theta = theta + dtheta
x = rr * math.cos(text_theta)
y = rr * math.sin(text_theta)
rot_theta = theta - 0.5 * math.pi
with gc:
gc.set_text_matrix(affine.affine_from_rotation(rot_theta))
gc.set_text_position(x, y)
gc.show_text(text)
def _percent_to_theta(self, percent):
""" Convert percent to the angle theta, in radians.
theta is the angle of the needle measured counterclockwise from
the horizontal (i.e. the traditional angle of polar coordinates).
"""
angle = (self.angle + (180.0 - 2 * self.angle) *
(self.max_percent - percent) / self.max_percent)
theta = math.radians(angle)
return theta
def _db_to_theta(self, db):
""" Convert db to the angle theta, in radians. """
percent = db_to_percent(db)
theta = self._percent_to_theta(percent)
return theta
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