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* @file 时值工具函数
* @description 提供音符时值相关的计算和转换
*/
import { NoteType } from '../models/types';
/**
* 音符类型到四分音符倍数的映射
*/
const NOTE_TYPE_TO_QUARTERS: Record<NoteType, number> = {
'1024th': 1/256,
'512th': 1/128,
'256th': 1/64,
'128th': 1/32,
'64th': 1/16,
'32nd': 1/8,
'16th': 1/4,
'eighth': 1/2,
'quarter': 1,
'half': 2,
'whole': 4,
'breve': 8,
'long': 16,
'maxima': 32
};
/**
* 四分音符倍数到音符类型的映射
*/
const QUARTERS_TO_NOTE_TYPE: Map<number, NoteType> = new Map([
[1/256, '1024th'],
[1/128, '512th'],
[1/64, '256th'],
[1/32, '128th'],
[1/16, '64th'],
[1/8, '32nd'],
[1/4, '16th'],
[1/2, 'eighth'],
[1, 'quarter'],
[2, 'half'],
[4, 'whole'],
[8, 'breve'],
[16, 'long'],
[32, 'maxima']
]);
/**
* 获取音符类型的四分音符倍数
* @param type 音符类型
* @returns 四分音符倍数
*/
export function getNoteTypeQuarters(type: NoteType): number {
return NOTE_TYPE_TO_QUARTERS[type];
}
/**
* 从四分音符倍数获取音符类型
* @param quarters 四分音符倍数
* @returns 音符类型或 undefined
*/
export function getNoteTypeFromQuarters(quarters: number): NoteType | undefined {
return QUARTERS_TO_NOTE_TYPE.get(quarters);
}
/**
* 计算附点后的时值倍数
* @param baseQuarters 基础时值（四分音符倍数）
* @param dots 附点数量
* @returns 附点后的时值
*/
export function applyDots(baseQuarters: number, dots: number): number {
let total = baseQuarters;
let dotValue = baseQuarters / 2;
for (let i = 0; i < dots; i++) {
total += dotValue;
dotValue /= 2;
}
return total;
}
/**
* 将 divisions 时值转换为四分音符倍数
* @param duration divisions 时值
* @param divisions 每四分音符的 divisions
* @returns 四分音符倍数
*/
export function divisionsToQuarters(duration: number, divisions: number): number {
return duration / divisions;
}
/**
* 将四分音符倍数转换为 divisions 时值
* @param quarters 四分音符倍数
* @param divisions 每四分音符的 divisions
* @returns divisions 时值
*/
export function quartersToDivisions(quarters: number, divisions: number): number {
return quarters * divisions;
}
/**
* 将 divisions 时值转换为秒
* @param duration divisions 时值
* @param divisions 每四分音符的 divisions
* @param tempo 速度（每分钟四分音符数）
* @returns 秒数
*/
export function divisionsToSeconds(duration: number, divisions: number, tempo: number): number {
const quarters = divisionsToQuarters(duration, divisions);
return (quarters * 60) / tempo;
}
/**
* 将秒转换为 divisions 时值
* @param seconds 秒数
* @param divisions 每四分音符的 divisions
* @param tempo 速度
* @returns divisions 时值
*/
export function secondsToDivisions(seconds: number, divisions: number, tempo: number): number {
const quarters = (seconds * tempo) / 60;
return quartersToDivisions(quarters, divisions);
}
/**
* 计算连音符的实际时值
* @param writtenDuration 书写时值
* @param actualNotes 实际音符数
* @param normalNotes 等效正常音符数
* @returns 实际时值
*/
export function calculateTupletDuration(
writtenDuration: number,
actualNotes: number,
normalNotes: number
): number {
return writtenDuration * normalNotes / actualNotes;
}
/**
* 获取音符类型的中文名称
* @param type 音符类型
* @returns 中文名称
*/
export function getNoteTypeName(type: NoteType): string {
const names: Record<NoteType, string> = {
'1024th': '1024分音符',
'512th': '512分音符',
'256th': '256分音符',
'128th': '128分音符',
'64th': '64分音符',
'32nd': '32分音符',
'16th': '16分音符',
'eighth': '八分音符',
'quarter': '四分音符',
'half': '二分音符',
'whole': '全音符',
'breve': '二全音符',
'long': '四全音符',
'maxima': '八全音符'
};
return names[type];
}
/**
* 获取简谱中的时值表示（下划线数量）
* @param type 音符类型
* @returns 下划线数量（负数表示增时线）
*/
export function getJianpuUnderlines(type: NoteType): number {
// 以四分音符为基准（0条下划线）
// 八分音符 = 1条，十六分 = 2条，三十二分 = 3条
// 二分音符 = -1（用横线表示），全音符 = -3
const underlines: Record<NoteType, number> = {
'1024th': 8,
'512th': 7,
'256th': 6,
'128th': 5,
'64th': 4,
'32nd': 3,
'16th': 2,
'eighth': 1,
'quarter': 0,
'half': -1,
'whole': -2,
'breve': -3,
'long': -4,
'maxima': -5
};
return underlines[type];
}
/**
* 计算小节的总时值（以 divisions 为单位）
* @param beats 拍数
* @param beatType 每拍的音符类型分母
* @param divisions 每四分音符的 divisions
* @returns 小节总时值
*/
export function getMeasureDuration(
beats: number | number[],
beatType: number | number[],
divisions: number
): number {
const totalBeats = Array.isArray(beats)
? beats.reduce((a, b) => a + b, 0)
: beats;
const type = Array.isArray(beatType) ? beatType[0] : beatType;
// 每拍时值 = 4 / beatType 个四分音符
const beatsInQuarters = totalBeats * (4 / type);
return beatsInQuarters * divisions;
}
/**
* 格式化时值为可读字符串
* @param quarters 四分音符倍数
* @returns 可读字符串
*/
export function formatDuration(quarters: number): string {
const noteType = getNoteTypeFromQuarters(quarters);
if (noteType) {
return getNoteTypeName(noteType);
}
// 检查是否是附点时值
for (let dots = 1; dots <= 3; dots++) {
for (const [baseQuarters, type] of QUARTERS_TO_NOTE_TYPE) {
if (Math.abs(applyDots(baseQuarters, dots) - quarters) < 0.0001) {
const dotStr = dots === 1 ? '附点' : dots === 2 ? '复附点' : '三重附点';
return `${dotStr}${getNoteTypeName(type)}`;
}
}
}
// 返回四分音符倍数
return `${quarters}个四分音符`;
}
/**
* 检查时值是否需要符杠（是否小于四分音符）
* @param type 音符类型
* @returns 是否需要符杠
*/
export function needsBeam(type: NoteType): boolean {
return NOTE_TYPE_TO_QUARTERS[type] < 1;
}
/**
* 获取符杠数量
* @param type 音符类型
* @returns 符杠数量（0表示不需要符杠）
*/
export function getBeamCount(type: NoteType): number {
const beamCounts: Partial<Record<NoteType, number>> = {
'eighth': 1,
'16th': 2,
'32nd': 3,
'64th': 4,
'128th': 5,
'256th': 6,
'512th': 7,
'1024th': 8
};
return beamCounts[type] ?? 0;
}
/**
* 判断音符类型的大小关系
* @param type1 类型1
* @param type2 类型2
* @returns 负数表示 type1 更短，0表示相等，正数表示 type1 更长
*/
export function compareNoteTypes(type1: NoteType, type2: NoteType): number {
return NOTE_TYPE_TO_QUARTERS[type1] - NOTE_TYPE_TO_QUARTERS[type2];
}
/**
* 获取比指定类型短一级的音符类型
* @param type 音符类型
* @returns 更短的音符类型或 undefined
*/
export function getShorterNoteType(type: NoteType): NoteType | undefined {
const quarters = NOTE_TYPE_TO_QUARTERS[type];
return QUARTERS_TO_NOTE_TYPE.get(quarters / 2);
}
/**
* 获取比指定类型长一级的音符类型
* @param type 音符类型
* @returns 更长的音符类型或 undefined
*/
export function getLongerNoteType(type: NoteType): NoteType | undefined {
const quarters = NOTE_TYPE_TO_QUARTERS[type];
return QUARTERS_TO_NOTE_TYPE.get(quarters * 2);
}
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