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

13 files changed, 90 insertions, 32 deletions

diff --git a/.eslintrc b/.eslintrc
index cfe653c2b8..7c6e734d9a 100644
--- a/.eslintrc
+++ b/.eslintrc
@@ -33,6 +33,10 @@ overrides:
       worker: true
     rules:
       no-restricted-globals: [2, addEventListener, blur, close, closed, confirm, defaultStatus, defaultstatus, error, event, external, find, focus, frameElement, frames, history, innerHeight, innerWidth, isFinite, isNaN, length, location, locationbar, menubar, moveBy, moveTo, name, onblur, onerror, onfocus, onload, onresize, onunload, open, opener, opera, outerHeight, outerWidth, pageXOffset, pageYOffset, parent, print, removeEventListener, resizeBy, resizeTo, screen, screenLeft, screenTop, screenX, screenY, scroll, scrollbars, scrollBy, scrollTo, scrollX, scrollY, status, statusbar, stop, toolbar, top]
+  - files: ["build/generate-images.js"]
+    rules:
+      import/no-unresolved: [0]
+      import/no-extraneous-dependencies: [0]
 
 rules:
   accessor-pairs: [2]
diff --git a/Makefile b/Makefile
index 4ee3e9b704..3ab86245c5 100644
--- a/Makefile
+++ b/Makefile
@@ -648,34 +648,8 @@ update-translations:
 
 .PHONY: generate-images
 generate-images:
-	$(eval TMPDIR := $(shell mktemp -d 2>/dev/null || mktemp -d -t 'gitea-temp'))
-	mkdir -p $(TMPDIR)/images
-	inkscape -f $(PWD)/assets/logo.svg -w 880 -h 880 -e $(PWD)/public/img/gitea-lg.png
-	inkscape -f $(PWD)/assets/logo.svg -w 512 -h 512 -e $(PWD)/public/img/gitea-512.png
-	inkscape -f $(PWD)/assets/logo.svg -w 192 -h 192 -e $(PWD)/public/img/gitea-192.png
-	inkscape -f $(PWD)/assets/logo.svg -w 120 -h 120 -jC -i layer1 -e $(TMPDIR)/images/sm-1.png
-	inkscape -f $(PWD)/assets/logo.svg -w 120 -h 120 -jC -i layer2 -e $(TMPDIR)/images/sm-2.png
-	composite -compose atop $(TMPDIR)/images/sm-2.png $(TMPDIR)/images/sm-1.png $(PWD)/public/img/gitea-sm.png
-	inkscape -f $(PWD)/assets/logo.svg -w 200 -h 200 -e $(PWD)/public/img/avatar_default.png
-	inkscape -f $(PWD)/assets/logo.svg -w 180 -h 180 -e $(PWD)/public/img/favicon.png
-	inkscape -f $(PWD)/assets/logo.svg -w 128 -h 128 -e $(TMPDIR)/images/128-raw.png
-	inkscape -f $(PWD)/assets/logo.svg -w 64 -h 64 -e $(TMPDIR)/images/64-raw.png
-	inkscape -f $(PWD)/assets/logo.svg -w 32 -h 32 -jC -i layer1 -e $(TMPDIR)/images/32-1.png
-	inkscape -f $(PWD)/assets/logo.svg -w 32 -h 32 -jC -i layer2 -e $(TMPDIR)/images/32-2.png
-	composite -compose atop $(TMPDIR)/images/32-2.png $(TMPDIR)/images/32-1.png $(TMPDIR)/images/32-raw.png
-	inkscape -f $(PWD)/assets/logo.svg -w 16 -h 16 -jC -i layer1 -e $(TMPDIR)/images/16-raw.png
-	zopflipng -m -y $(TMPDIR)/images/128-raw.png $(TMPDIR)/images/128.png
-	zopflipng -m -y $(TMPDIR)/images/64-raw.png $(TMPDIR)/images/64.png
-	zopflipng -m -y $(TMPDIR)/images/32-raw.png $(TMPDIR)/images/32.png
-	zopflipng -m -y $(TMPDIR)/images/16-raw.png $(TMPDIR)/images/16.png
-	rm -f $(TMPDIR)/images/*-*.png
-	convert $(TMPDIR)/images/16.png $(TMPDIR)/images/32.png \
-					$(TMPDIR)/images/64.png $(TMPDIR)/images/128.png \
-					$(PWD)/public/img/favicon.ico
-	convert -flatten $(PWD)/public/img/favicon.png $(PWD)/public/img/apple-touch-icon.png
-
-	rm -rf $(TMPDIR)/images
-	$(foreach file, $(shell find public/img -type f -name '*.png' ! -name 'loading.png'),zopflipng -m -y $(file) $(file);)
+	npm install --no-save --no-package-lock xmldom fabric imagemin-zopfli
+	node build/generate-images.js
 
 .PHONY: pr\#%
 pr\#%: clean-all
diff --git a/assets/logo.svg b/assets/logo.svg
index ac1594adb8..bfd50a0c90 100644
--- a/assets/logo.svg
+++ b/assets/logo.svg
@@ -115,6 +115,7 @@
   <g
      inkscape:groupmode="layer"
      id="layer3"
+     class="detail-remove"
      inkscape:label="Layer 3"
      style="display:inline">
     <g
@@ -157,4 +158,4 @@
          style="fill:none;stroke:#609926;stroke-width:2.68000007;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1" />
     </g>
   </g>
-</svg>
+</svg>
\ No newline at end of file
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);
+
diff --git a/docs/content/doc/advanced/hacking-on-gitea.en-us.md b/docs/content/doc/advanced/hacking-on-gitea.en-us.md
index e6ffe908e9..5c3f199944 100644
--- a/docs/content/doc/advanced/hacking-on-gitea.en-us.md
+++ b/docs/content/doc/advanced/hacking-on-gitea.en-us.md
@@ -155,10 +155,9 @@ Note: When working on frontend code, set `USE_SERVICE_WORKER` to `false` in `app
 
 SVG icons are built using the `make svg` target which compiles the icon sources defined in `build/generate-svg.js` into the output directory `public/img/svg`. Custom icons can be added in the `web_src/svg` directory.
 
-### Building Images
+### Building the Logo
 
-To build the images, ImageMagick, `inkscape` and `zopflipng` binaries must be available in
-your `PATH` to run `make generate-images`.
+The PNG versions of the logo are built from a single SVG source file `assets/logo.svg` using the `make generate-images` target. To run it, Node.js and npm must be available. The same process can also be used to generate a custom logo PNGs from a SVG source file. It's possible to remove parts of the SVG logo for the favicon build by adding a `detail-remove` class to the SVG nodes to be removed.
 
 ### Updating the API
 
diff --git a/public/img/apple-touch-icon.png b/public/img/apple-touch-icon.png
index d2def0bdc7..e23ba5999d 100644
--- a/public/img/apple-touch-icon.png
+++ b/public/img/apple-touch-icon.png
diff --git a/public/img/avatar_default.png b/public/img/avatar_default.png
index 455155db10..346edb4bbe 100644
--- a/public/img/avatar_default.png
+++ b/public/img/avatar_default.png
diff --git a/public/img/favicon.ico b/public/img/favicon.ico
deleted file mode 100644
index 681d76d33a..0000000000
--- a/public/img/favicon.ico
+++ /dev/null
diff --git a/public/img/favicon.png b/public/img/favicon.png
index 30d3313594..5ad5af21bf 100644
--- a/public/img/favicon.png
+++ b/public/img/favicon.png
diff --git a/public/img/gitea-192.png b/public/img/gitea-192.png
index 12caba8d5d..05bf6d6de7 100644
--- a/public/img/gitea-192.png
+++ b/public/img/gitea-192.png
diff --git a/public/img/gitea-512.png b/public/img/gitea-512.png
index 456abfa0c0..7b32fb33b6 100644
--- a/public/img/gitea-512.png
+++ b/public/img/gitea-512.png
diff --git a/public/img/gitea-lg.png b/public/img/gitea-lg.png
index 682ceaf7be..e50c6cf4d1 100644
--- a/public/img/gitea-lg.png
+++ b/public/img/gitea-lg.png
diff --git a/public/img/gitea-sm.png b/public/img/gitea-sm.png
index 405f40f170..0ae375c5c6 100644
--- a/public/img/gitea-sm.png
+++ b/public/img/gitea-sm.png