PNG (Portable Network Graphics)

Every valid PNG file begins with an immutable 8-byte signature: ```hex 89 50 4E 47 0D 0A 1A 0A ``` This signature detects transmission errors, carriage return corruption, and binary integrity before parsing subsequent chunks. Following the signature, all PNG data is packaged into structured 4-part chunks (Length, 4-character Chunk Type, Chunk Data, and 32-bit CRC Checksum): Critical PNG Chunks: 1. `IHDR` (Image Header): Must be the first chunk; defines width, height, bit depth, color type, compression method, filter method, and interlace method. 2. `PLTE` (Palette Table): Mandatory for indexed color images, optional for truecolor. 3. `IDAT` (Image Data): Contains the filtered and DEFLATE-compressed scanline pixel streams (can span multiple sequential IDAT chunks). 4. `IEND` (Image Trailer): The final chunk marking end of stream.

Before DEFLATE compresses pixel bytes, PNG runs each horizontal row through one of five reversible mathematical filters to maximize repeated zero-byte patterns:

Automating PNG optimization using OptiPNG and Oxipng compression passes to strip redundant metadata chunks and re-evaluate optimal filters:

// Modern Sharp Node.js Pipeline with Maximum PNG Compression
const sharp = require('sharp');

async function compressPngLossless(inputPath, outputPath) {
  await sharp(inputPath)
    .png({
      compressionLevel: 9, // Maximum DEFLATE effort
      adaptiveFiltering: true, // Dynamically select best Paeth/Sub filter per scanline
      palette: false, // Maintain full 24-bit/32-bit truecolor fidelity
      force: true
    })
    .toFile(outputPath);

  console.log('PNG optimized successfully with zero visual loss.');
}