# Copyright 2018 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Clef logic for OMR.
A Clef object maps y positions on the staff to the MIDI pitch of the natural
note at the y position.
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import librosa
from moonlight.music import constants
from moonlight.protobuf import musicscore_pb2
class Clef(object):
"""Represents a clef which maps y positions to MIDI notes.
Attributes:
center_line_pitch: A _ScalePitch representing the center line (3rd line of
the staff).
"""
center_line_pitch = None
def y_position_to_midi(self, y_position):
return (self.center_line_pitch + y_position).midi
class TrebleClef(Clef):
"""Represents a treble clef."""
def __init__(self):
self.center_line_pitch = _ScalePitch(constants.MAJOR_SCALE,
librosa.note_to_midi('B4'))
self.glyph = musicscore_pb2.Glyph.CLEF_TREBLE
class BassClef(Clef):
"""Represents a bass clef."""
def __init__(self):
self.center_line_pitch = _ScalePitch(constants.MAJOR_SCALE,
librosa.note_to_midi('D3'))
self.glyph = musicscore_pb2.Glyph.CLEF_BASS
class _ScalePitch(object):
"""A natural note which can be offset to get another note.
Attributes:
scale: The scale which this pitch is based on. A list of MIDI pitch values
spanning one octave.
index: The index of the pitch's pitch class within the scale.
octave: The index of the octave that the pitch is in, relative to the octave
spanning the scale notes.
"""
def __init__(self, scale, midi):
self.scale = scale
self.index = scale.index(midi % constants.NUM_SEMITONES_PER_OCTAVE)
self.octave = (midi - scale[0]) // 12
@property
def midi(self):
"""The MIDI value for the pitch."""
notes_per_octave = constants.NUM_SEMITONES_PER_OCTAVE
return self.scale[self.index] + notes_per_octave * self.octave
@property
def pitch_index(self):
"""The index of the pitch in the C major scale."""
return self.index + len(self.scale) * self.octave
def __add__(self, interval):
"""Returns the natural note `interval` away on `self.scale`."""
pitch = _ScalePitch(self.scale, self.midi)
pitch_index = self.pitch_index + interval
pitch.index = pitch_index % len(self.scale)
pitch.octave = pitch_index // len(self.scale)
return pitch
