getImageMimeType static method

String getImageMimeType(List<int> bytes)

Decode the first 2 bytes of the picture stream

• JPEG: 0xFF 0xD8
• PNG: 0x89 0x50
• GIF: 0x47 0x49
• BMP: 0x42 0x4D
• TIFF: 0x4D 0x4D or 0x49 0x49

Implementation

static String getImageMimeType(List<int> bytes) {
  final typeBytes = bytes.sublist(0, 2);
  bool equal(List<int> a, List<int> b) {
    if (a.length != b.length) return false;
    for (int i = 0; i < a.length; i++) {
      if (a[i] != b[i]) {
        return false;
      }
    }
    return true;
  }

  if (equal(typeBytes, [0xFF, 0xD8])) {
    return "image/jpeg";
  } else if (equal(typeBytes, [0x89, 0x50])) {
    return "image/png";
  } else if (equal(typeBytes, [0x47, 0x49])) {
    return "image/gif";
  } else if (equal(typeBytes, [0x42, 0x4D])) {
    return "image/bmp";
  } else if (equal(typeBytes, [0x4D, 0x4D]) ||
      equal(typeBytes, [0x49, 0x49])) {
    return "image/tiff";
  } else {
    return "";
  }
}