1234567891011121314151617181920212223242526272829303132333435
/** * Return mime type of a file * @param headerString - header of file * List here: * https://en.wikipedia.org/wiki/List_of_file_signatures * https://mimesniff.spec.whatwg.org/#matching-an-image-type-pattern */export function mimeType(imgFile: Uint8Array) {  // Get mime type  const arr = imgFile.subarray(0, 4);  let header = "";  for (let i = 0; i < arr.length; i++) {    header += arr[i].toString(16);  }
  let type = "unknown";  switch (header) {    case "89504e47":      type = "image/png";      break;    case "47494638":      type = "image/gif";      break;    case "ffd8ffe0":    case "ffd8ffe1":    case "ffd8ffe2":      type = "image/jpeg";      break;    default:      type = "unknown";      break;  }  return type;}