PowerShell script to prefix files by DateTime from file name or Date Taken from EXIF data

Rename-ItemsByDateTimeFromFileNameOrExifData.ps1

function Get-DateTakenFromExifData {
  param([String] $filePath)

  try { 
    $imgData = New-Object System.Drawing.Bitmap($filePath)
    try {
      [Byte[]]$dateTakenExifData = $imgData.GetPropertyItem(36867).Value
      [String]$dateString = [System.Text.Encoding]::ASCII.GetString($dateTakenExifData)
      return [DateTime]::ParseExact($dateString, "yyyy:MM:dd HH:mm:ss`0", $null) 
    }
    finally {
      $imgData.Dispose()
    }
  }
  catch { }

  return $null
}

function Get-DateFromFileName {
  param([String] $fileName)

  if ($fileName -match '\d{8}') {
    return [DateTime]::ParseExact($Matches[0], "yyyyMMdd", [Globalization.CultureInfo]::CreateSpecificCulture('en-GB'))
  }
}

function Get-DateTimeFromFileName {
  param([String] $fileName)

  if ($fileName -match '\d{8}_\d{6}') {
    return [DateTime]::ParseExact($Matches[0], "yyyyMMdd_HHmmss", [Globalization.CultureInfo]::CreateSpecificCulture('en-GB'))
  }
}

function Get-DateTimeForFilePrefix {
  param([System.IO.FileInfo] $fileInfo)

  $date = Get-DateTimeFromFileName ($fileInfo.Name)
  if ($date) {
    return $date
  }

  $date = Get-DateFromFileName ($fileInfo.Name)
  if ($date) {
    return $date
  }

  $date = Get-DateTakenFromExifData ($fileInfo.FullPath)
  if ($date) {
    return $date
  }

  return $fileInfo.LastWriteTime
}

Get-ChildItem | ForEach-Object {
  $from = $_.Name
  $dateTimeForPrefix = Get-DateTimeForFilePrefix $_
  $to = "$($dateTimeForPrefix.ToString('yyyy-MM-dd HH.mm.ss')) $from"
  Write-Host "Renaming `"$from`" to `"$to`""
  Rename-Item $from $to
}