toPng

Convert an image to PNG format.

Signature

function toPng(input: Buffer, options?: PngOptions): Promise<Buffer>
function toPngSync(input: Buffer, options?: PngOptions): Buffer

Parameters

Parameter	Type	Description
input	Buffer	Image buffer
options	PngOptions	PNG encoding options (optional)

PngOptions

interface PngOptions {
  compression?: number;  // 0-9, default: 6
}

Returns

Buffer - PNG encoded image

Examples

Basic Conversion

import { toPng } from 'bun-image-turbo';

const png = await toPng(buffer);
await Bun.write('output.png', png);

With Compression Level

// Fast compression (larger file)
const fast = await toPng(buffer, { compression: 1 });

// Balanced (default)
const balanced = await toPng(buffer, { compression: 6 });

// Maximum compression (smaller file, slower)
const max = await toPng(buffer, { compression: 9 });

Sync Version

import { toPngSync } from 'bun-image-turbo';

const png = toPngSync(buffer, { compression: 6 });

Preserve Transparency

// PNG preserves alpha channel
const webpWithAlpha = Buffer.from(await Bun.file('logo.webp').arrayBuffer());
const png = await toPng(webpWithAlpha);
// Transparency is preserved

From JPEG

const jpeg = Buffer.from(await Bun.file('photo.jpg').arrayBuffer());
const png = await toPng(jpeg);
// Note: No quality loss, but file will be larger

Compression Levels

Level	Speed	File Size
0	Fastest	Largest
1-2	Fast	Large
3-5	Medium	Medium
6	Balanced	Balanced (default)
7-8	Slow	Smaller
9	Slowest	Smallest

When to Use PNG

Use PNG for:

• Images with transparency
• Screenshots
• Graphics with text
• Logos and icons
• When lossless quality is required

Don't use PNG for:

• Photos (use JPEG or WebP)
• Large images (file sizes can be huge)
• Web delivery (WebP is usually better)

Notes

• PNG is always lossless
• Supports alpha channel (transparency)
• File sizes can be large for photos
• Compression level affects encoding time, not quality

See Also

• toJpeg() - For photos without transparency
• toWebp() - For smaller files with transparency
• transform() - For resize + convert in one operation