Picture modification with PowerShell

What can we do if we need to resize, crop more than 2000 picture? Later it needs to repeat this task regularly, as a scheduled task. The answer is automatizing with PowerShell on Windows OS. I don’t like add-ons or 3rd party things importing into a corporate environment. I decided to write my code without any 3rd party things.

Firs I ask for help from .NET, because the PowerShell easily use. I loaded the .NET Framework System.Drawing class.

$a = [reflection.assembly]::LoadWithPartialName("System.Drawing")

After this I can modify any pictures. I got the following modify rules:

  • The final picture width and height must be 96×96 pixel
  • Portrait images must to insert on a white square
  • Landscape images must to cut to square


Here is my picture modification function:

Function ReDraw-Picture{
	Param (
	Write-Host 'ReDraw-Picture function started'
	$SizeLimit= 96
	$Source= $DriveLetter + $Sourcepic.Name
	$Destination= $Global:TempDir +"\"+ $Sourcepic.Name
	$OldBitmap = new-object System.Drawing.Bitmap $Source
	$text1 = $Sourcepic.Name
	$text = "  ReDrawing $text1, save as $Destination"
	Write-Host $text
	if ($OldBitmap.Height -gt $SizeLimit) { 
	 	if ($OldBitmap.Width -lt $OldBitmap.Height) {
			$offset = [int] (($newH - $newW)/2)
			$NewBitmap = new-object System.Drawing.Bitmap $SizeLimit,$SizeLimit
			$g.clear([System.Drawing.Color]::White )
        	$g.InterpolationMode = [System.Drawing.Drawing2D.InterpolationMode]::HighQualityBicubic 
        	$g.DrawImage($OldBitmap, $offset, 0, $newW, $newH)   
				$newH = $SizeLimit
				$newW = [int]($OldBitmap.Width*$SizeLimit/$OldBitmap.Height)
				$offset = [int] (($newW - $newH)/2)
				$NewBitmap = new-object System.Drawing.Bitmap $SizeLimit,$SizeLimit
        		$g.InterpolationMode = [System.Drawing.Drawing2D.InterpolationMode]::HighQualityBicubic 
        		$g.DrawImage($OldBitmap, -$offset, 0, $newW, $newH)  
		$NewBitmap.Save($Destination, ([system.drawing.imaging.imageformat]::jpeg))
	Write-Host 'ReDraw-Picture function finished'


The parameters of the ReDraw-Picture function are the picture name, and the picture location. It will save the modified picture into a TempDir directory, not overwrite the original one.


One thought on “Picture modification with PowerShell”

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