bmp2gifBackground.ps1

Add-Type -AssemblyName PresentationCore
Add-Type -AssemblyName system.drawing
[void][reflection.assembly]::LoadWithPartialName("System.Windows.Forms")

$delay = 35
$filename = "animation.gif"
$fileStream = New-Object System.IO.FileStream $filename, 'Create'
$gif = New-Object -TypeName System.Windows.Media.Imaging.GifBitmapEncoder

foreach ($frame in Get-ChildItem ".\*.bmp") {

    $bmp = [System.Drawing.Bitmap]::FromFile($frame.fullname)
    $hbmp = $bmp.GetHbitMap()
    $bmpsrc = [System.Windows.Interop.Imaging]::CreateBitmapSourceFromHBitmap($hbmp, [System.IntPtr]::Zero, 'Empty', [System.Windows.Media.Imaging.BitmapSizeOptions]::FromEmptyOptions())
    For ($i = 0; $i -lt $delay; $i++) {
        $gif.Frames.Add([System.Windows.Media.Imaging.BitmapFrame]::Create($bmpsrc))
    }
    $hbmp = $bmp = $null
}

$gif.Save($fileStream)
$fileStream.Flush()
$fileStream.Dispose()

$bytes = [System.IO.File]::ReadAllBytes("animation.gif")
$applicationExtension = [byte[]](33, 255, 11, 78, 69, 84, 83, 67, 65, 80, 69, 50, 46, 48, 3, 1, 0, 0, 0)
$newBytes = New-Object -TypeName 'System.Collections.Generic.List[byte]'
$newBytes.AddRange([byte[]]$bytes[0..12]);
$newBytes.AddRange($applicationExtension);
$newBytes.AddRange([byte[]]$bytes[13..($bytes.count)])
$streamE = New-Object System.IO.MemoryStream(,$newBytes)
$wpImage = [System.Drawing.Image]::FromStream($streamE)
#$wpImage.Save("animation-with-delay.gif", "gif") #Save gif with the new delay

[System.Windows.Forms.Application]::EnableVisualStyles();
$form = new-object Windows.Forms.Form
$form.Width =  $wpImage.Size.Width;
$form.Height =  $wpImage.Size.Height;
$form.TopMost = $false
$form.FormBorderStyle = [System.Windows.Forms.BorderStyle]::None;
$Form.ControlBox = $False
$pictureBox = new-object Windows.Forms.PictureBox
$pictureBox.Width =  $wpImage.Size.Width;
$pictureBox.Height =  $wpImage.Size.Height;
$pictureBox.Image = $wpImage;
$form.controls.add($pictureBox)
$form.Add_Shown( { $form.Activate() } )
$form.ShowDialog()| Out-Null