Correct GIF file extensions in a folder tree

correct-gif-file-extensions-in-a-folder-tree.md

Correct GIF file extensions in a folder tree

The script searches all files with extension .gif and appends the real extension, if necessary

The attached powershell script searches all files with extension .gif in the specified folder (including its subfolders), examines the file by checking the file header and appends the correct extension for the file content found.
The file formats JPG, PNG, WebM and WebP are recognized.

correct_gif_file_extensions.ps1

if (!$args[0]) {
    Write-Host "No Folder specified!"
    Exit
}

$path = $args[0]

$riff = 0x52,0x49,0x46,0x46
$webm = 0x1A,0x45,0xDF,0xA3
$jpg = 0xFF,0xD8,0xFF
$png = 0x89,0x50,0x4E,0x47

foreach ($item in Get-ChildItem $path -Recurse -Filter *.gif)
{
    $fn = $item.FullName
    $bytes = Get-Content -LiteralPath $fn -Encoding byte -TotalCount 4
    if (($bytes[0] -eq $riff[0]) -and ($bytes[1] -eq $riff[1]) -and ($bytes[2] -eq $riff[2]) -and ($bytes[3] -eq $riff[3])) {
        $newName = "$fn.webp"
        Rename-Item -Path $fn -NewName $newName
        Write-Host "$fn.webp"
    }
    if (($bytes[0] -eq $webm[0]) -and ($bytes[1] -eq $webm[1]) -and ($bytes[2] -eq $webm[2]) -and ($bytes[3] -eq $webm[3])) {
        $newName = "$fn.webm"
        Rename-Item -Path $fn -NewName $newName
        Write-Host "$fn.webm"
    }
    if (($bytes[0] -eq $jpg[0]) -and ($bytes[1] -eq $jpg[1]) -and ($bytes[2] -eq $jpg[2])) {
        $newName = "$fn.jpg"
        Rename-Item -LiteralPath $fn -NewName $newName
        Write-Host "$fn.jpg"
    }
    if (($bytes[0] -eq $png[0]) -and ($bytes[1] -eq $png[1]) -and ($bytes[2] -eq $png[2]) -and ($bytes[3] -eq $png[3])) {
        $newName = "$fn.png"
        Rename-Item -LiteralPath $fn -NewName $newName
        Write-Host "$fn.png"
    }
}