【Rust GUI开发入门】编写一个本地音乐播放器（8. 从文件中提取歌曲元信息）

本系列教程对应的代码已开源在 Github zeedle

目的是从.mp3/.flac/.wav/...文件中提取歌曲名称/艺术家/音频时长信息/歌词信息/专辑封面

添加依赖

使用lofty这个全能解析库，将其添加到Cargo.toml中：

lofty = "0.22.4"

解析元信息

解析歌名/歌手/时长

这些信息在应用启动后，即刻被加载到音乐列表面板中（SongInfo已于前几篇文章中定义）：

/// Read meta info from audio file `fp`, return a SongInfo
pub fn read_meta_info(fp: &PathBuf) -> Option<SongInfo> {if let Ok(tagged) = lofty::read_from_path(fp) {let dura = tagged.properties().duration().as_secs_f32();if let Some(tag) = tagged.primary_tag() {let song_name = tag.title();let song_name = song_name.as_deref().unwrap_or(fp.file_stem().map(|x| x.to_str()).flatten().unwrap_or("unknown"),);let singer_name = tag.artist();let singer_name = singer_name.as_deref().unwrap_or("unknown");let item = SongInfo {id: 0,song_path: fp.display().to_shared_string(),song_name: song_name.into(),singer: singer_name.into(),duration: format!("{:02}:{:02}", (dura as u32) / 60, (dura as u32) % 60).to_shared_string(),};return Some(item);}}None
}

解析歌词

歌词只有在播放该文件时才应该被加载，所以单独解析：

/// Read lyrics from audio file `p`, return a list of LyricItem
pub fn read_lyrics(p: PathBuf) -> Vec<LyricItem> {if let Ok(tagged) = lofty::read_from_path(&p) {if let Some(tag) = tagged.primary_tag() {if let Some(lyric_item) = tag.get(&ItemKey::Lyrics) {let mut lyrics = lyric_item.value().text().unwrap().split("\n").map(|line| {let (time_str, text) = line.split_once(']').unwrap_or(("", ""));let time_str = time_str.trim_start_matches('[');let dura = time_str.split(':').map(|x| x.parse::<f32>().unwrap_or(0.)).rev().reduce(|acc, x| acc + x * 60.).unwrap_or(0.);LyricItem {time: dura,text: text.to_shared_string(),duration: 0.0,}}).filter(|ins| ins.time > 0. && !ins.text.is_empty()).collect::<Vec<_>>();for i in 0..lyrics.len() - 1 {lyrics[i].duration = lyrics[i + 1].time - lyrics[i].time;}lyrics.last_mut().map(|ins| ins.duration = 100.0);return lyrics;}}}return Vec::new();
}

解析专辑封面

同上，该图像只有在播放该文件时才应该被加载，所以单独解析：

/// Read album cover from audio file `p`
pub fn read_album_cover(p: PathBuf) -> Option<(Vec<u8>, u32, u32)> {if let Ok(tagged) = lofty::read_from_path(&p) {if let Some(tag) = tagged.primary_tag() {if let Some(picture) = tag.pictures().iter().find(|pic| {pic.pic_type() == PictureType::CoverFront|| pic.pic_type() == PictureType::CoverBack}) {if let Ok(img) = image::load_from_memory(picture.data()) {let rgba = img.into_rgba8();let (width, height) = rgba.dimensions();let buffer = rgba.into_vec();return Some((buffer, width, height));}}}}None
}