let data: Data? = try? Data(contentsOf: Bundle.main.url(forResource: "exposure_tab_gray_arrow_right@2x", withExtension: "png")!)

internal struct ImageHeaderData {
    static var PNG: [UInt8] = [0x89]
    static var JPEG: [UInt8] = [0xFF]
    static var GIF: [UInt8] = [0x47]
    static var BMP: [UInt8] = [0x42]
    static var TIFF_01: [UInt8] = [0x49]
    static var TIFF_02: [UInt8] = [0x4D]
  }

do {
    let start = (data! as NSData).bytes.bindMemory(to: UInt8.self, capacity: data!.count)
    let byte: UInt8? = UnsafeBufferPointer(start: start, count: 1).first
    print(byte as Any)

        switch byte {
        case ImageHeaderData.PNG:
            return .PNG
        case ImageHeaderData.JPEG:
            return .JPEG
        case ImageHeaderData.GIF:
            return .GIF
        case ImageHeaderData.TIFF_01:
            fallthrough
        case ImageHeaderData.TIFF_02:
            return .TIFF
        case ImageHeaderData.BMP:
            return .BMP
           }
}

do {
    var buffer = [UInt8](repeating: 0, count: 1)
    (data! as NSData).getBytes(&buffer, range: NSRange(location: 0, length: 1))
    print(buffer as Any)

    switch buffer {
        case ImageHeaderData.PNG:
            return .PNG
        case ImageHeaderData.JPEG:
            return .JPEG
        case ImageHeaderData.GIF:
            return .GIF
        case ImageHeaderData.TIFF_01:
            fallthrough
        case ImageHeaderData.TIFF_02:
            return .TIFF
        case ImageHeaderData.BMP:
            return .BMP
           }
}