demo/js/optipng.js
function isDataURI(filename) {
  return String.prototype.startsWith ?
      filename.startsWith(dataURIPrefix) :
      filename.indexOf(dataURIPrefix) === 0;
}
function isDataURI(filename) {
  return String.prototype.startsWith ?
      filename.startsWith(dataURIPrefix) :
      filename.indexOf(dataURIPrefix) === 0;
}
function isDataURI ( filename ) { return String . prototype . startsWith ? filename . startsWith ( dataURIPrefix ) : filename . indexOf ( dataURIPrefix ) === 0 ; }
Indicates whether filename is a base64 data URI.
Indicates whether filename is a base64 data URI .