Rework 'make generate-images' (#12316)

* Rework 'make generate-images'

- Remove external dependencies and replace it with a node script that
  does does the same.
- Move detail removal from gitea-sm.png to favicon.png
- Remove favicon.ico and its generation, it is unused and we already serve
  favicon.png in its place.

Fixes: https://github.com/go-gitea/gitea/issues/12314

* use proper centering value for preserveAspectRatio

* fix lint

* use fabric

* better linting fix

* fix typo

* mention detail-remove class in docs

1 files changed, 80 insertions, 0 deletions

diff --git a/build/generate-images.js b/build/generate-images.js
new file mode 100755
index 0000000000..7a00395a5b
--- /dev/null
+++ b/build/generate-images.js
@@ -0,0 +1,80 @@
+#!/usr/bin/env node
+'use strict';
+
+const imageminZopfli = require('imagemin-zopfli');
+const {fabric} = require('fabric');
+const {DOMParser, XMLSerializer} = require('xmldom');
+const {readFile, writeFile} = require('fs').promises;
+const {resolve} = require('path');
+
+function exit(err) {
+  if (err) console.error(err);
+  process.exit(err ? 1 : 0);
+}
+
+function loadSvg(svg) {
+  return new Promise((resolve) => {
+    fabric.loadSVGFromString(svg, (objects, options) => {
+      resolve({objects, options});
+    });
+  });
+}
+
+async function generate(svg, outputFile, {size, bg, removeDetail} = {}) {
+  const parser = new DOMParser();
+  const serializer = new XMLSerializer();
+  const document = parser.parseFromString(svg);
+
+  if (removeDetail) {
+    for (const el of Array.from(document.getElementsByTagName('g') || [])) {
+      for (const attribute of Array.from(el.attributes || [])) {
+        if (attribute.name === 'class' && attribute.value === 'detail-remove') {
+          el.parentNode.removeChild(el);
+        }
+      }
+    }
+  }
+
+  svg = serializer.serializeToString(document);
+
+  const {objects, options} = await loadSvg(svg);
+  const canvas = new fabric.Canvas();
+  canvas.setDimensions({width: size, height: size});
+  const ctx = canvas.getContext('2d');
+  ctx.scale(options.width ? (size / options.width) : 1, options.height ? (size / options.height) : 1);
+
+  if (bg) {
+    canvas.add(new fabric.Rect({
+      left: 0,
+      top: 0,
+      height: size * (1 / (size / options.height)),
+      width: size * (1 / (size / options.width)),
+      fill: 'white',
+    }));
+  }
+
+  canvas.add(fabric.util.groupSVGElements(objects, options));
+  canvas.renderAll();
+
+  let png = Buffer.from([]);
+  for await (const chunk of canvas.createPNGStream()) {
+    png = Buffer.concat([png, chunk]);
+  }
+
+  png = await imageminZopfli({more: true})(png);
+  await writeFile(outputFile, png);
+}
+
+async function main() {
+  const svg = await readFile(resolve(__dirname, '../assets/logo.svg'), 'utf8');
+  await generate(svg, resolve(__dirname, '../public/img/gitea-lg.png'), {size: 880});
+  await generate(svg, resolve(__dirname, '../public/img/gitea-512.png'), {size: 512});
+  await generate(svg, resolve(__dirname, '../public/img/gitea-192.png'), {size: 192});
+  await generate(svg, resolve(__dirname, '../public/img/gitea-sm.png'), {size: 120});
+  await generate(svg, resolve(__dirname, '../public/img/avatar_default.png'), {size: 200});
+  await generate(svg, resolve(__dirname, '../public/img/favicon.png'), {size: 180, removeDetail: true});
+  await generate(svg, resolve(__dirname, '../public/img/apple-touch-icon.png'), {size: 180, bg: true});
+}
+
+main().then(exit).catch(exit);
+