Resize-Image.ps1

using namespace System.Drawing

Add-Type -AssemblyName System.Drawing

function Resize-Picture {
    [CmdletBinding()]
    param(
        [Parameter(Mandatory)]
        [string] $SourcePath,

        [Parameter(Mandatory)]
        [int] $Width,

        [Parameter(Mandatory)]
        [int] $Height,

        [Parameter(Mandatory)]
        [string] $DestinationPath
    )

    end {
        try {
            $DestinationPath = $PSCmdlet.GetUnresolvedProviderPathFromPSPath($DestinationPath)

            $source   = Get-Item $SourcePath -ErrorAction Stop
            $inStream = $source.OpenRead()

            $sourceImage = [Image]::FromStream($inStream)
            $newSize     = [Size]::new($Width, $Height)
            $destination = [Bitmap]::new($sourceImage, $newSize)
            $destination.Save($DestinationPath)
        }
        catch {
            $PSCmdlet.ThrowTerminatingError($_)
        }
        finally {
            $sourceImage, $inStream, $destination | ForEach-Object Dispose
        }
    }
}