Get-FileType.ps1

function Get-FileType {
    <#
        .SYNOPSIS
            Try to get the file type based on it's file signature.
        .DESCRIPTION
            This function uses Get-FileSignature by Boe Prox and a list of
            known file signatures to try to find the file type of a given file.
        .EXAMPLE
            Get-FileType c:\path\to\file.pdf
        .LINK
            https://gallery.technet.microsoft.com/scriptcenter/Get-FileSignature-f5ae19f5
        .NOTES
            Author: Øyvind Kallstad
            Date: 15.12.2014
            Version: 1.0
    #>
    [CmdletBinding()]
    param (
        # Path to file.
        [Parameter(Position = 0, ValueFromPipelineByPropertyName)]
        [string[]] $Path
    )

    begin {
        # description, hex signature, byte offset, byte limit
        $fileSignatures = @(
            @('JPG/JPEG','FFD8FF',0,3),
            @('Portable Network Graphics (PNG)','89504E470D0A1A0A',0,8),
            @('Graphics Interchange Format - GIF87a (GIF)','474946383761',0,6),
            @('Graphics Interchange Format - GIF89a (GIF)','474946383961',0,6),
            @('Icon (ICO)','00000100',0,4),
            @('MPEG-4 (MP4)','000000*66747970',0,8),
            @('MPEG-4 (MP4)','336770',0,3),
            @('Windows/DOS executable file (EXE/COM/DLL/DRV/PIF/OCX/OLB/SCR/CPL ++)','4D5A',0,2),
            @('Archive (RAR)','526172211A0700',0,7),
            @('Archive (RAR)','526172211A070100',0,8),
            @('Adobe Portable Document Format (PDF) / Forms Document file (FDF)','25504446',0,4),
            @('MPEG-1 Audio Layer 3 (MP3)','FFFB',0,2),
            @('MPEG-1 Audio Layer 3 (MP3)','494433',0,3),
            @('ISO9660 CD/DVD image (ISO)','4344303031','0x8001',5),
            @('ISO9660 CD/DVD image (ISO)','4344303031','0x8801',5),
            @('ISO9660 CD/DVD image (ISO)','4344303031','0x9001',5),
            @('Install Shield compressed file (CAB/HDR)','49536328',0,4),
            @('Microsoft cabinet file (CAB) / Powerpoint Packaged Presentation (PPZ) / Microsoft Access Snapshot Viewer file (SNP)','4D534346',0,4),
            @('Microsoft Windows Imaging Format file (WIM)','4D5357494D',0,5),
            @('Rich text format (RTF)','7B5C72746631',0,6),
            @('TrueType font file (TTF)','0001000000',0,5),
            @('Windows shell link (shortcut) file (LNK)','4C00000001140200',0,8),
            @('Windows Help (HLP/GID)','4C4E0200',0,4),
            @('Windows Help (HLP/GID)','3F5F0300',0,4),
            @('Windows Help (HLP)','0000FFFFFFFF',0,6),
            @('Windows Registry (REG/SUD)','52454745444954',0,7),
            @('Windows Registry (REG)','FFFE',0,2),
            @('Archive (ZIP/JAR)','504B0304',0,4),
            @('Microsoft security catalog file (CAT)','30',0,1),
            @('Windows memory dump (DMP)','5041474544554D50',0,8),
            @('Windows 64-bit memory dump (DMP)','5041474544553634',0,8),
            @('Windows minidump (DMP) / Windows heap dump (HDMP)','4D444D5093A7',0,6),
            @('Microsoft Compiled HTML Help (CHM/CHI)','49545346',0,4),
            @('Waveform Audio (WAV)','52494646*57415645',0,12)
        )
    }

    process {
        foreach ($filePath in $Path) {
            if (Test-Path $Path) {
                foreach($signature in $fileSignatures) {
                    if($thisSig = Get-FileSignature -Path $filePath -HexFilter $signature[1] -ByteOffset $signature[2] -ByteLimit $signature[3]) {
                        Write-Output (,([PSCustomObject] [Ordered] @{
                            Path = $filePath
                            FileType = ($signature[0])
                            HexSignature = $thisSig.HexSignature
                            ASCIISignature = $thisSig.ASCIISignature
                            Extension = $thisSig.Extension
                        }))
                    }
                }
            }
            else {
                Write-Warning "$filePath not found!"
            }
        }
    }
}