feat: opt-in JPEG-embed quality for image-to-PDF conversion

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

test/converters/imageToPdf.test.js

@@ -2,6 +2,7 @@ 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 { registerImageToPdfConverter } from '../../src/converters/imageToPdf.js';
 import { resolve, listTargetFormats } from '../../src/converters/registry.js';
 import { detectInputMime } from '../../src/mime.js';
@@ -33,4 +34,34 @@ describe('image to PDF converter', () => {
     const detected = await detectInputMime(outputPath);
     expect(detected.mime).toBe('application/pdf');
   });
+
+  it('embeds a JPEG instead of a PNG when a quality is given, shrinking the output for a noisy image', async () => {
+    const inputPath = path.join(tmpDir, 'noisy.png');
+    await sharp({
+      create: {
+        width: 256,
+        height: 256,
+        channels: 3,
+        noise: { type: 'gaussian', mean: 128, sigma: 40 },
+      },
+    })
+      .png()
+      .toFile(inputPath);
+
+    const defaultOutputPath = path.join(tmpDir, 'default.pdf');
+    const compressedOutputPath = path.join(tmpDir, 'compressed.pdf');
+    const entry = resolve('png', 'pdf');
+
+    await entry.convert(inputPath, defaultOutputPath);
+    await entry.convert(inputPath, compressedOutputPath, { quality: 20 });
+
+    const compressedDetected = await detectInputMime(compressedOutputPath);
+    expect(compressedDetected.mime).toBe('application/pdf');
+
+    const [defaultStat, compressedStat] = await Promise.all([
+      fs.stat(defaultOutputPath),
+      fs.stat(compressedOutputPath),
+    ]);
+    expect(compressedStat.size).toBeLessThan(defaultStat.size);
+  });
 });