code: private function readBlipJPEG()
      {
          // offset: 0; size: 2; recVer and recInstance
  
          // bit: 4-15; mask: 0xFFF0; recInstance
          $recInstance = (0xFFF0 & Xls::getUInt2d($this->data, $this->pos)) >> 4;
  
          $length = Xls::getInt4d($this->data, $this->pos + 4);
          $recordData = substr($this->data, $this->pos + 8, $length);
  
          // move stream pointer to next record
          $this->pos += 8 + $length;
  
          $pos = 0;
  
          // offset: 0; size: 16; rgbUid1 (MD4 digest of)
          $rgbUid1 = substr($recordData, 0, 16);
          $pos += 16;
  
          // offset: 16; size: 16; rgbUid2 (MD4 digest), only if $recInstance = 0x46B or 0x6E3
          if (in_array($recInstance, [0x046B, 0x06E3])) {
              $rgbUid2 = substr($recordData, 16, 16);
              $pos += 16;
          }
  
          // offset: var; size: 1; tag
          $tag = ord($recordData[$pos]);
          $pos += 1;
  
          // offset: var; size: var; the raw image data
          $data = substr($recordData, $pos);
  
          $blip = new Blip();
          $blip->setData($data);
  
          $this->object->setBlip($blip);
      }
docs: Read BlipJPEG record. Holds raw JPEG image data.