strip-png-metadata.js

var fs = require('fs');

fs.readFile('./map-pin-default.png', function(err, buffer) {
    if(err) {
        console.log(err);
    }else {
        var list = parsePng(buffer);
        var tEXt = list[1];
        var iTXt = list[2];

        console.log(list);
        console.log(tEXt.data.toString());
        console.log(iTXt.data.toString('UTF8'));
    }
});

function parsePng(buffer) {
    var list = [];
    var position = 8;
    var length = buffer.length;

    if(isPng(buffer)) {
        while(position < length) {
            var size = buffer.readUIntBE(position, 4);
            var eofChunk = position + size + 12;
            var chunkBuffer = buffer.slice(position, eofChunk);
            var chunk = {};

            chunk.size = size;
            chunk.type = chunkBuffer.toString('utf8', 4, 8);
            chunk.data = chunkBuffer.slice(8, 8 + size);
            chunk.crc = chunkBuffer.readUIntBE(8 + size, 4);

            list.push(chunk);
            position = eofChunk;
        }
    }

    return list;
}

function isPng(buffer) {
    if (
        buffer[0] === 0x89 && buffer[1] === 0x50 && buffer[2] === 0x4E && buffer[3] === 0x47 &&
        buffer[4] === 0x0d && buffer[5] === 0x0a && buffer[6] === 0x1a && buffer[7] === 0x0a
    ) {
		return true;
	}
    return false;
}