add minification precommit hook

.gitignore

@@ -7,4 +7,6 @@ node_modules
 .idea
 
 *.sublime-project
-*.sublime-workspace
+*.sublime-workspace
+
+build/imagemin/already-minified.json

build/imagemin/dirty.mjs

@@ -0,0 +1,46 @@
+// @ts-check
+import imagemin from "imagemin";
+import { promises as fs } from "fs";
+
+import gifsicle from "imagemin-gifsicle";
+import pngquant from "imagemin-pngquant";
+import mozjpeg from "imagemin-mozjpeg";
+import { getAlreadyMinified, getDirtyImages, saveAlreadyMinified } from "./lib.mjs";
+
+const files =
+  process.argv.length > 2 ? process.argv.slice(2) : getDirtyImages();
+
+(async () => {
+  const alreadyMinified = await getAlreadyMinified();
+  for (const [i, file] of files.entries()) {
+    if (alreadyMinified.has(file)) {
+      console.log("Skipping", file, ", in already-minified.json");
+      files.splice(i, 1);
+    }
+  }
+
+  const minified = await imagemin(files, {
+    plugins: [
+      gifsicle(),
+      pngquant({ quality: [0.6, 0.8] }),
+      mozjpeg({ quality: 80 }),
+    ],
+  });
+
+  for (const file of minified) {
+    const prev = await fs.stat(file.sourcePath);
+    alreadyMinified.add(file.sourcePath);
+    console.log(
+      `${file.sourcePath} => ${prev.size} to ${file.data.length} (${(
+        (file.data.length / prev.size) *
+        100
+      ).toFixed(2)}%)`
+    );
+    await fs.writeFile(file.sourcePath, file.data);
+  }
+
+  await saveAlreadyMinified(alreadyMinified);
+})().catch((e) => {
+  console.error(e);
+  process.exit(1);
+});

build/imagemin/lib.mjs

@@ -0,0 +1,33 @@
+// @ts-check
+import { resolve } from "path";
+import { execSync } from "child_process";
+import { fileURLToPath } from "url";
+import { promises as fs } from "fs";
+
+const extensions = [".png", ".jpg", ".gif"];
+const __dirname = fileURLToPath(new URL(".", import.meta.url));
+
+export const alreadyMinifiedPath = resolve(__dirname, "already-minified.json");
+export const repoPath = resolve(__dirname, "..", "..");
+
+export const getDirtyImages = () =>
+  execSync("git ls-files --others")
+    .toString()
+    .split("\n")
+    .map((l) => l.trim())
+    .filter((l) => extensions.some((e) => l.endsWith(e)))
+    .map((l) => resolve(repoPath, l));
+
+export const getAlreadyMinified = async () =>
+  new Set(
+    JSON.parse(
+      await fs.readFile(alreadyMinifiedPath, "utf-8").catch(() => "[]")
+    )
+  );
+
+/** @param {Set<string>} alreadyMinified */
+export const saveAlreadyMinified = (alreadyMinified) =>
+  fs.writeFile(
+    alreadyMinifiedPath,
+    JSON.stringify([...alreadyMinified], null, 2)
+  );

package.json

@@ -10,17 +10,25 @@
   },
   "scripts": {
     "check-lfs": "node ./build/check-lfs.js",
+    "minify": "node ./build/imagemin/dirty.mjs",
     "prepare": "husky install"
   },
   "devDependencies": {
     "gulp": "^4.0.2",
     "husky": "^7.0.0",
     "lint-staged": "^12.3.3",
-    "shelljs": "^0.8.5"
+    "shelljs": "^0.8.5",
+    "imagemin": "^8.0.1",
+    "imagemin-pngquant": "^9.0.2",
+    "imagemin-gifsicle": "^7.0.0",
+    "imagemin-mozjpeg": "^10.0.0"
   },
   "lint-staged": {
     "*.{gif,mp4,jpg,png,GIF,MP4,JPG,PNG}": [
       "yarn check-lfs"
+    ],
+    "*.{gif,jpg,png,GIF,JPG,PNG}": [
+      "yarn minify"
     ]
   },
   "resolutions": {