feat: add image to PDF converter

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

src/converters/imageToPdf.js

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+import fs from 'node:fs/promises';
+import sharp from 'sharp';
+import { PDFDocument } from 'pdf-lib';
+import { register } from './registry.js';
+
+const IMAGE_FORMATS = ['jpg', 'jpeg', 'png', 'webp', 'gif', 'tiff', 'avif'];
+
+async function convert(inputPath, outputPath) {
+  const pngBuffer = await sharp(inputPath).png().toBuffer();
+  const metadata = await sharp(pngBuffer).metadata();
+
+  const pdfDoc = await PDFDocument.create();
+  const page = pdfDoc.addPage([metadata.width, metadata.height]);
+  const embeddedImage = await pdfDoc.embedPng(pngBuffer);
+
+  page.drawImage(embeddedImage, {
+    x: 0,
+    y: 0,
+    width: metadata.width,
+    height: metadata.height,
+  });
+
+  const pdfBytes = await pdfDoc.save();
+  await fs.writeFile(outputPath, pdfBytes);
+}
+
+export function registerImageToPdfConverter() {
+  for (const sourceFormat of IMAGE_FORMATS) {
+    register({ family: 'image', sourceFormat, targetFormat: 'pdf', convert });
+  }
+}

test/converters/imageToPdf.test.js

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+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 { registerImageToPdfConverter } from '../../src/converters/imageToPdf.js';
+import { resolve, listTargetFormats } from '../../src/converters/registry.js';
+import { detectInputMime } from '../../src/mime.js';
+
+let tmpDir;
+
+beforeAll(async () => {
+  registerImageToPdfConverter();
+  tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), 'converter-image-to-pdf-'));
+});
+
+afterAll(async () => {
+  await fs.rm(tmpDir, { recursive: true, force: true });
+});
+
+describe('image to PDF converter', () => {
+  it('registers pdf as a target for every image format', () => {
+    expect(listTargetFormats('png')).toContain('pdf');
+    expect(listTargetFormats('jpg')).toContain('pdf');
+  });
+
+  it('converts a PNG fixture into a valid PDF', async () => {
+    const inputPath = path.join(import.meta.dirname, '..', 'fixtures', 'sample.png');
+    const outputPath = path.join(tmpDir, 'output.pdf');
+    const entry = resolve('png', 'pdf');
+
+    await entry.convert(inputPath, outputPath);
+
+    const detected = await detectInputMime(outputPath);
+    expect(detected.mime).toBe('application/pdf');
+  });
+});