get_raw_image_data.kt

// Get the image's Uri from shared intent etc.
val imageSelected: Uri = intent.getParcelableExtra(Intent.EXTRA_STREAM)
try {
    // get the raw file data of the photo
    val mInputPFD = contentResolver.openFileDescriptor(imageSelected, "r")
    val mContentFileDescriptor = mInputPFD.fileDescriptor
    val fIS = FileInputStream(mContentFileDescriptor)
    val mGraphicBuffer = ByteArrayOutputStream()
    val buf = ByteArray(1024)
    while (true) {
        val readNum = fIS.read(buf)
        if (readNum == -1) break
        mGraphicBuffer.write(buf, 0, readNum)
    }

    // Generate the checksum
    mChecksum = generateChecksum(mGraphicBuffer)
} catch (e: Exception) {
    e.printStackTrace()
}