feat: add bidirectional ICO image converter

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

package-lock.json

@@ -7,7 +7,6 @@
     "": {
       "name": "file-converter",
       "version": "0.1.0",
-      "hasInstallScript": true,
       "dependencies": {
         "@prisma/client": "^6.19.3",
         "docx": "^9.7.1",
@@ -16,6 +15,7 @@
         "express": "^5.2.1",
         "express-rate-limit": "^8.6.1",
         "file-type": "^22.0.1",
+        "icojs": "^1.0.0",
         "mammoth": "^1.12.0",
         "markdown-it": "^15.0.0",
         "multer": "^2.2.0",
@@ -47,6 +47,12 @@
         "url": "https://github.com/sponsors/Borewit"
       }
     },
+    "node_modules/@canvas/image-data": {
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/@canvas/image-data/-/image-data-1.1.0.tgz",
+      "integrity": "sha512-QdObRRjRbcXGmM1tmJ+MrHcaz1MftF2+W7YI+MsphnsCrmtyfS0d5qJbk0MeSbUeyM/jCb0hmnkXPsy026L7dA==",
+      "license": "MIT"
+    },
     "node_modules/@emnapi/core": {
       "version": "2.0.0-alpha.3",
       "resolved": "https://registry.npmjs.org/@emnapi/core/-/core-2.0.0-alpha.3.tgz",
@@ -2056,6 +2062,12 @@
       "integrity": "sha512-iD3898SR7sWVRHbiQv+sHUtHnMvC1o3nW5rAcqnq3uOn07DSAppZYUkIGslDz6gXC7HfunPe7YVBgoEJASPcHA==",
       "license": "MIT"
     },
+    "node_modules/bmp-ts": {
+      "version": "1.0.9",
+      "resolved": "https://registry.npmjs.org/bmp-ts/-/bmp-ts-1.0.9.tgz",
+      "integrity": "sha512-cTEHk2jLrPyi+12M3dhpEbnnPOsaZuq7C45ylbbQIiWgDFZq4UVYPEY5mlqjvsj/6gJv9qX5sa+ebDzLXT28Vw==",
+      "license": "MIT"
+    },
     "node_modules/body-parser": {
       "version": "2.3.0",
       "resolved": "https://registry.npmjs.org/body-parser/-/body-parser-2.3.0.tgz",
@@ -2690,6 +2702,33 @@
         }
       }
     },
+    "node_modules/decode-bmp": {
+      "version": "0.2.1",
+      "resolved": "https://registry.npmjs.org/decode-bmp/-/decode-bmp-0.2.1.tgz",
+      "integrity": "sha512-NiOaGe+GN0KJqi2STf24hfMkFitDUaIoUU3eKvP/wAbLe8o6FuW5n/x7MHPR0HKvBokp6MQY/j7w8lewEeVCIA==",
+      "license": "MIT",
+      "dependencies": {
+        "@canvas/image-data": "^1.0.0",
+        "to-data-view": "^1.1.0"
+      },
+      "engines": {
+        "node": ">=8.6.0"
+      }
+    },
+    "node_modules/decode-ico": {
+      "version": "0.4.1",
+      "resolved": "https://registry.npmjs.org/decode-ico/-/decode-ico-0.4.1.tgz",
+      "integrity": "sha512-69NZfbKIzux1vBOd31al3XnMnH+2mqDhEgLdpygErm4d60N+UwA5Sq5WFjmEDQzumgB9fElojGwWG0vybVfFmA==",
+      "license": "MIT",
+      "dependencies": {
+        "@canvas/image-data": "^1.0.0",
+        "decode-bmp": "^0.2.0",
+        "to-data-view": "^1.1.0"
+      },
+      "engines": {
+        "node": ">=8.6"
+      }
+    },
     "node_modules/deepmerge-ts": {
       "version": "7.1.5",
       "resolved": "https://registry.npmjs.org/deepmerge-ts/-/deepmerge-ts-7.1.5.tgz",
@@ -3637,6 +3676,22 @@
         "url": "https://opencollective.com/express"
       }
     },
+    "node_modules/icojs": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/icojs/-/icojs-1.0.0.tgz",
+      "integrity": "sha512-Ksd2dSS9PlN/KX2iymij7cBCa5aWOhqlZ0GMamRInCHMBlWYxyQQMfr/aURywO7psO49w8vrJGnHkySfxVKmVw==",
+      "license": "MIT",
+      "dependencies": {
+        "bmp-ts": "^1.0.9",
+        "decode-ico": "^0.4.1",
+        "file-type": "^22.0.1",
+        "jpeg-js": "^0.4.4",
+        "pngjs": "^7.0.0"
+      },
+      "engines": {
+        "node": ">=22.22.2"
+      }
+    },
     "node_modules/iconv-lite": {
       "version": "0.7.3",
       "resolved": "https://registry.npmjs.org/iconv-lite/-/iconv-lite-0.7.3.tgz",
@@ -3778,6 +3833,12 @@
         "jiti": "lib/jiti-cli.mjs"
       }
     },
+    "node_modules/jpeg-js": {
+      "version": "0.4.4",
+      "resolved": "https://registry.npmjs.org/jpeg-js/-/jpeg-js-0.4.4.tgz",
+      "integrity": "sha512-WZzeDOEtTOBK4Mdsar0IqEU5sMr3vSV2RqkAIzUEV2BHnUfKGyswWFPFwK5EeDo93K3FohSHbLAjj0s1Wzd+dg==",
+      "license": "BSD-3-Clause"
+    },
     "node_modules/js-yaml": {
       "version": "4.3.0",
       "resolved": "https://registry.npmjs.org/js-yaml/-/js-yaml-4.3.0.tgz",
@@ -5048,6 +5109,15 @@
         }
       }
     },
+    "node_modules/pngjs": {
+      "version": "7.0.0",
+      "resolved": "https://registry.npmjs.org/pngjs/-/pngjs-7.0.0.tgz",
+      "integrity": "sha512-LKWqWJRhstyYo9pGvgor/ivk2w94eSjE3RGVuzLGlr3NmD8bf7RcYGze1mNdEHRP6TRP6rMuDHk5t44hnTRyow==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=14.19.0"
+      }
+    },
     "node_modules/postcss": {
       "version": "8.5.24",
       "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.5.24.tgz",
@@ -5937,6 +6007,12 @@
         "node": ">=14.14"
       }
     },
+    "node_modules/to-data-view": {
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/to-data-view/-/to-data-view-1.1.0.tgz",
+      "integrity": "sha512-1eAdufMg6mwgmlojAx3QeMnzB/BTVp7Tbndi3U7ftcT2zCZadjxkkmLmd97zmaxWi+sgGcgWrokmpEoy0Dn0vQ==",
+      "license": "MIT"
+    },
     "node_modules/to-regex-range": {
       "version": "5.0.1",
       "resolved": "https://registry.npmjs.org/to-regex-range/-/to-regex-range-5.0.1.tgz",

package.json

@@ -22,6 +22,7 @@
     "express": "^5.2.1",
     "express-rate-limit": "^8.6.1",
     "file-type": "^22.0.1",
+    "icojs": "^1.0.0",
     "mammoth": "^1.12.0",
     "markdown-it": "^15.0.0",
     "multer": "^2.2.0",

src/converters/ico.js

@@ -0,0 +1,45 @@
+import fs from 'node:fs/promises';
+import sharp from 'sharp';
+import { decodeIco, encodeIco } from 'icojs';
+import { register } from './registry.js';
+import { sharpFormatName, buildFormatOptions } from './image.js';
+
+const IMAGE_FORMATS = ['jpg', 'jpeg', 'png', 'webp', 'gif', 'tiff', 'avif'];
+export const DEFAULT_ICON_SIZE = 256;
+
+export async function encodeIcoFromInput(input, size = DEFAULT_ICON_SIZE) {
+  const pngBuffer = await sharp(input).resize(size, size, { fit: 'contain' }).png().toBuffer();
+  return Buffer.from(await encodeIco([{ buffer: pngBuffer }]));
+}
+
+async function decodeIcoLargestImage(inputPath) {
+  const buffer = await fs.readFile(inputPath);
+  const images = await decodeIco(buffer, 'image/png');
+  return images.reduce((a, b) => (a.width * a.height >= b.width * b.height ? a : b));
+}
+
+export function registerIcoConverter() {
+  for (const format of IMAGE_FORMATS) {
+    register({
+      family: 'image',
+      sourceFormat: 'ico',
+      targetFormat: format,
+      convert: async (inputPath, outputPath, { quality } = {}) => {
+        const largest = await decodeIcoLargestImage(inputPath);
+        await sharp(Buffer.from(largest.buffer))
+          .toFormat(sharpFormatName(format), buildFormatOptions(format, quality))
+          .toFile(outputPath);
+      },
+    });
+
+    register({
+      family: 'image',
+      sourceFormat: format,
+      targetFormat: 'ico',
+      convert: async (inputPath, outputPath, { iconSize } = {}) => {
+        const icoBuffer = await encodeIcoFromInput(inputPath, iconSize ?? DEFAULT_ICON_SIZE);
+        await fs.writeFile(outputPath, icoBuffer);
+      },
+    });
+  }
+}

src/converters/image.js

@@ -3,7 +3,7 @@ import { register } from './registry.js';
 
 const IMAGE_FORMATS = ['jpg', 'jpeg', 'png', 'webp', 'gif', 'tiff', 'avif'];
 
-function sharpFormatName(format) {
+export function sharpFormatName(format) {
   return format === 'jpg' ? 'jpeg' : format;
 }
 

test/converters/ico.test.js

@@ -0,0 +1,99 @@
+import { describe, it, expect, beforeAll, afterAll } from 'vitest';
+import fs from 'node:fs/promises';
+import path from 'node:path';
+import os from 'node:os';
+import sharp from 'sharp';
+import { registerIcoConverter, encodeIcoFromInput, DEFAULT_ICON_SIZE } from '../../src/converters/ico.js';
+import { resolve, listTargetFormats } from '../../src/converters/registry.js';
+import { detectInputMime } from '../../src/mime.js';
+
+let tmpDir;
+
+beforeAll(async () => {
+  registerIcoConverter();
+  tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), 'converter-ico-'));
+});
+
+afterAll(async () => {
+  await fs.rm(tmpDir, { recursive: true, force: true });
+});
+
+describe('ICO converter registration', () => {
+  it('registers ico as both a source and a target for every image format', () => {
+    expect(listTargetFormats('ico')).toContain('png');
+    expect(listTargetFormats('ico')).toContain('jpg');
+    expect(listTargetFormats('png')).toContain('ico');
+    expect(listTargetFormats('jpg')).toContain('ico');
+  });
+});
+
+describe('encodeIcoFromInput', () => {
+  it('defaults to a 256x256 icon when no size is given', async () => {
+    const inputPath = path.join(import.meta.dirname, '..', 'fixtures', 'sample.png');
+    const icoBuffer = await encodeIcoFromInput(inputPath);
+
+    const outputPath = path.join(tmpDir, 'default-size.ico');
+    await fs.writeFile(outputPath, icoBuffer);
+    const detected = await detectInputMime(outputPath);
+    expect(detected.mime).toBe('image/x-icon');
+  });
+
+  it('produces an icon at the requested size', async () => {
+    const inputPath = path.join(import.meta.dirname, '..', 'fixtures', 'sample.png');
+    const icoBuffer = await encodeIcoFromInput(inputPath, 32);
+
+    const { decodeIco } = await import('icojs');
+    const [image] = await decodeIco(icoBuffer, 'image/png');
+    expect(image.width).toBe(32);
+    expect(image.height).toBe(32);
+  });
+});
+
+describe('ico -> image conversion', () => {
+  it('converts an ICO fixture to PNG, picking the largest embedded image', async () => {
+    const source = path.join(import.meta.dirname, '..', 'fixtures', 'sample.png');
+    const icoPath = path.join(tmpDir, 'multi.ico');
+
+    const small = await sharp(source).resize(16, 16).png().toBuffer();
+    const large = await sharp(source).resize(48, 48).png().toBuffer();
+    const { encodeIco } = await import('icojs');
+    await fs.writeFile(icoPath, Buffer.from(await encodeIco([{ buffer: small }, { buffer: large }])));
+
+    const outputPath = path.join(tmpDir, 'from-ico.png');
+    const entry = resolve('ico', 'png');
+    await entry.convert(icoPath, outputPath);
+
+    const meta = await sharp(outputPath).metadata();
+    expect(meta.width).toBe(48);
+    expect(meta.height).toBe(48);
+  });
+});
+
+describe('image -> ico conversion', () => {
+  it('converts a PNG fixture to a valid ICO at the requested size', async () => {
+    const inputPath = path.join(import.meta.dirname, '..', 'fixtures', 'sample.png');
+    const outputPath = path.join(tmpDir, 'output.ico');
+    const entry = resolve('png', 'ico');
+
+    await entry.convert(inputPath, outputPath, { iconSize: 48 });
+
+    const detected = await detectInputMime(outputPath);
+    expect(detected.mime).toBe('image/x-icon');
+
+    const { decodeIco } = await import('icojs');
+    const [image] = await decodeIco(await fs.readFile(outputPath), 'image/png');
+    expect(image.width).toBe(48);
+  });
+
+  it('defaults to 256px when no iconSize is given', async () => {
+    const inputPath = path.join(import.meta.dirname, '..', 'fixtures', 'sample.png');
+    const outputPath = path.join(tmpDir, 'output-default.ico');
+    const entry = resolve('png', 'ico');
+
+    await entry.convert(inputPath, outputPath);
+
+    const { decodeIco } = await import('icojs');
+    const [image] = await decodeIco(await fs.readFile(outputPath), 'image/png');
+    expect(image.width).toBe(DEFAULT_ICON_SIZE);
+  });
+});