ICO to PNG converter demo for Windows PowerShell

icoconverter-win.ps1

function Convert-IcoToPng ([string]$icofile) {
	# Runtime validation
	if ($PSVersionTable.PSEdition -eq 'Core') {return}
	if (-not $icofile -or -not (Test-Path $icofile)) {return}
	# ICO validation
	$signature = Get-Content -Path $icofile -Encoding Byte -TotalCount 6 -ErrorAction 0
	if (([System.BitConverter]::ToInt32(($signature[0..3]),0)) -ne 0x10000) {return}
	if (([System.BitConverter]::ToInt16(($signature[4,5]),0)) -gt 1) {return} # single-size

	Add-Type -AssemblyName System.Runtime.WindowsRuntime
	$runtimeMethods = [System.WindowsRuntimeSystemExtensions].GetMethods()
	$asTaskGeneric = ($runtimeMethods | Where-Object {$_.Name -eq 'AsTask' -and $_.GetParameters().Count -eq 1 -and $_.GetParameters()[0].ParameterType.Name -eq 'IAsyncOperation`1' })[0]
	function AwaitOperation ($WinRtTask, $ResultType) {
		$asTaskSpecific = $asTaskGeneric.MakeGenericMethod($ResultType)
		$netTask = $asTaskSpecific.Invoke($null, @($WinRtTask))
		$null = $netTask.Wait()
		$netTask.Result
	}
	$asTask = ($runtimeMethods | Where-Object {$_.Name -eq 'AsTask' -and $_.GetParameters().Count -eq 1 -and $_.GetParameters()[0].ParameterType.Name -eq 'IAsyncAction' })[0]
	function AwaitAction ($WinRtTask) {
		$netTask = $asTask.Invoke($null, @($WinRtTask))
		$null = $netTask.Wait()
	}

	# Reference WinRT assemblies
	$null = [Windows.Storage.StorageFile, Windows.Storage, ContentType=WindowsRuntime]
	$null = [Windows.Graphics.Imaging.BitmapDecoder, Windows.Graphics, ContentType=WindowsRuntime]

	$file = Resolve-Path -LiteralPath $icofile
	$inputFile = AwaitOperation ([Windows.Storage.StorageFile]::GetFileFromPathAsync($file)) ([Windows.Storage.StorageFile])
	$inputFolder = AwaitOperation ($inputFile.GetParentAsync()) ([Windows.Storage.StorageFolder])
	$inputStream = AwaitOperation ($inputFile.OpenReadAsync()) ([Windows.Storage.Streams.IRandomAccessStreamWithContentType])
	$decoder = AwaitOperation ([Windows.Graphics.Imaging.BitmapDecoder]::CreateAsync($inputStream)) ([Windows.Graphics.Imaging.BitmapDecoder])

	$bitmap = AwaitOperation $decoder.GetSoftwareBitmapAsync() ([Windows.Graphics.Imaging.SoftwareBitmap])

	# Write SoftwareBitmap to output file
	$outputFileName = $inputFile.Name -replace ($inputFile.FileType + "$"), ".png"
	$outputFile = AwaitOperation ($inputFolder.CreateFileAsync($outputFileName, [Windows.Storage.CreationCollisionOption]::ReplaceExisting)) ([Windows.Storage.StorageFile])
	$outputStream = AwaitOperation ($outputFile.OpenAsync([Windows.Storage.FileAccessMode]::ReadWrite)) ([Windows.Storage.Streams.IRandomAccessStream])
	$encoder = AwaitOperation ([Windows.Graphics.Imaging.BitmapEncoder]::CreateAsync([Windows.Graphics.Imaging.BitmapEncoder]::PngEncoderId, $outputStream)) ([Windows.Graphics.Imaging.BitmapEncoder])
	$encoder.SetSoftwareBitmap($bitmap)
	$encoder.IsThumbnailGenerated = $false # PNG encoder doesn't like the thumbnail generation

	# Finishing & cleanup
	AwaitAction $encoder.FlushAsync()

	if ($bitmap) {$bitmap.Dispose()}
	if ($inputStream) {$inputStream.Dispose()}
	if ($outputStream) {$outputStream.Dispose()}
} # END Convert-IcoToPng