My-PowerShell

$image = New-Object -ComObject Wia.ImageFile
Get-ChildItem -Recurse -Include *.jpg -Path "..\images" | foreach {
$file = $_.fullname
$image.LoadFile($file)
if ( $image.Width -gt $image.Height) {
Remove-Item -Path $file -Force
}
}

If (-not (Test-Path "dossier_test")) { New-Item -ItemType Directory -Name "dossier_test" }