cyp/app/js/art.js

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JavaScript
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2019-03-20 05:56:39 +08:00
import * as mpd from "./mpd.js";
import * as parser from "./parser.js";
let cache = {};
const SIZE = 64;
async function getImageData(songUrl) {
let data = [];
let offset = 0;
while (1) {
let params = ["albumart", `"${mpd.escape(songUrl)}"`, offset];
let lines = await mpd.command(params.join(" "));
data = data.concat(lines[2]);
let metadata = parser.linesToStruct(lines.slice(0, 2));
if (data.length >= Number(metadata["size"])) { return data; }
offset += Number(metadata["binary"]);
}
}
async function bytesToImage(bytes) {
let blob = new Blob([bytes]);
let image = document.createElement("img");
image.src = URL.createObjectURL(blob);
return new Promise(resolve => {
image.onload = () => resolve(image);
});
}
async function resize(image) {
let canvas = document.createElement("canvas");
canvas.width = SIZE;
canvas.height = SIZE;
let ctx = canvas.getContext("2d");
ctx.drawImage(image, 0, 0, SIZE, SIZE);
return new Promise(resolve => canvas.toBlob(resolve));
}
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export async function get(artist, album, songUrl = null) {
let key = `${artist}-${album}`;
if (key in cache) { return cache[key]; }
if (!songUrl) { return null; }
// promise to be returned in the meantime
let resolve;
let promise = new Promise(res => resolve = res);
cache[key] = promise;
try {
let data = await getImageData(songUrl);
let bytes = new Uint8Array(data);
let image = await bytesToImage(bytes);
let blob = await resize(image);
let url = URL.createObjectURL(blob);
cache[key] = url;
resolve(url);
} catch (e) {
cache[key] = null;
}
return cache[key];
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}