feat(background): add other in-game backgrouds (1/2)

Co-authored-by: yueqiaocertik <yueqiaocertik@users.noreply.github.com>

libs/background.js

@@ -0,0 +1,63 @@
+import path from 'path';
+import fs from 'fs';
+import sharp from "sharp";
+
+export default class Background {
+  #config
+  #rootDir
+  #backgroundFolder
+  #extractFolder
+  #files
+
+  constructor(config, rootDir) {
+    this.#config = config;
+    this.#rootDir = rootDir;
+    this.#backgroundFolder = path.join(rootDir, config.folder.operator, '_share', config.folder.background);
+    this.#extractFolder = path.join(this.#backgroundFolder, 'extracted');
+  }
+
+  async process() {
+    this.#files = fs.readdirSync(this.#extractFolder).filter((f) => {
+      return f.endsWith('.png') && f.includes('_left');
+    })
+    if (this.#files.length + 2 !== fs.readdirSync(this.#backgroundFolder).length) {
+      await Promise.all(this.#files.map(async (f) => {
+        const filenamePrefix = path.parse(f).name.replace('_left', '');
+        await this.#composite(filenamePrefix, '.png');
+      }))
+    } else {
+      console.log('Background images already exist, skip generation.')
+    }
+  }
+
+  async #composite(filenamePrefix, fileExt) {
+    const image = sharp(path.join(this.#extractFolder, `${filenamePrefix}_left${fileExt}`))
+    const metadata = await image.metadata()
+
+    image
+      .resize(2 * metadata.width, metadata.height, {
+        kernel: sharp.kernel.nearest,
+        fit: 'contain',
+        position: 'left top',
+        background: { r: 255, g: 255, b: 255, alpha: 0 }
+      })
+      .composite([
+        {
+          input: path.join(this.#extractFolder, `${filenamePrefix}_right${fileExt}`),
+          top: 0,
+          left: metadata.width,
+        },
+      ])
+      .toFile(path.join(this.#backgroundFolder, `${filenamePrefix}${fileExt}`));
+  }
+
+  getFilesToCopy(publicAssetsDir) {
+    return this.#files.map((f) => {
+      return {
+        filename: f.replace('_left', ''),
+        source: path.join(this.#backgroundFolder),
+        target: path.join(publicAssetsDir, this.#config.folder.background)
+      };
+    })
+  }
+}