RunKit + npm: bin-grammar

var { uint32, uint8, enumeration, binary, crc32, binString, selector, magic, loop, parse } = require("bin-grammar"); // header const ihdrGrammar = [ uint32('width'), uint32('height'), uint8('bitDepth'), enumeration('colorType', { choices: { greyscale: 0, trueColor: 2, indexedColor: 3, grayscaleWithAlpha: 4, trueColorWithAlpha: 6 } }), enumeration('compressionMethod', { choices: { deflate: 0 } }), enumeration('filterMethod', { choices: { adaptive: 0 } }), enumeration('interlaceMethod', { choices: { none: 0, adam7: 1 } }), ] // binary image data const idatGrammar = [binary('data')]; // no content const iendGrammar = []; // definition of a chunk const chunkGrammar = [ uint32('length'), crc32('crc', [ binString('name', { size: 4 }), selector('data', { sizeField: 'length', field: 'name', flatten: true, select: [ { match: 'IHDR', struct: ihdrGrammar }, { match: 'IDAT', struct: idatGrammar }, { match: 'IEND', struct: iendGrammar }, ], }), ]), ]; // png "shell", in principle just a magic number and a list of chunks const pngGrammar = [ magic('magic', { data: Buffer.from('89504e470d0a1a0a', 'hex') }), loop('chunks', { struct: chunkGrammar }) ]; // smallest possible 1x1 px transparent png const buffer = Buffer.from( '89504E470D0A1A0A0000000D494844520000000100000001' + '0100000000376EF9240000001049444154789C6260010000' + '00FFFF03000006000557BFABD40000000049454E44AE426082', 'hex' ); // parse the png const result = parse(pngGrammar, buffer); // show result JSON.stringify(result, null, ' ');