Create icon from an image file.

ConvertTo-Icon.ps1

function ConvertTo-Icon {
    [CmdletBinding(DefaultParameterSetName = 'BySuffix')]
    Param (
        # Specifies the source image filename
        [Parameter(Mandatory = $true, ValueFromPipeline = $true)]
        [string]$Path
        ,
        # the name of the .ico file
        [Parameter(Mandatory = $true, ParameterSetName = 'ByLiteralName')]
        [string]$Destination
        ,
        # what to append to the end of the source path to give our new filename
        [Parameter(Mandatory = $false, ParameterSetName = 'BySuffix')]
        [string]$Suffix = '.ico'
    )
    Process {
        if ($PSCmdlet.ParameterSetName -eq 'BySuffix') {
            $Destination = '{0}{1}' -f $Path, $Suffix
        }
        try {
            $outstream = [System.IO.File]::OpenWrite($Destination)
            $sourceImage = [System.Drawing.Bitmap]([System.Drawing.Image]::FromFile($Path))
            [System.Drawing.Icon]::FromHandle($sourceImage.GetHicon()).Save($outstream)
            (New-Object -TypeName 'PSObject' -Property @{SourceImage = $Path; IconPath = $Destination})
        } finally {
            $outstream.Dispose()
        }
    }
}