Resize-ThumbnailPhoto.ps1

 <#
.SYNOPSIS
    Resize photos to a specified size, 648 by default
    Rename them and place them in a 'resized' folder

.EXAMPLE
    Get-ChildItem -Path C:\Picures | Resize-ThumbnailPhoto
#>

Function Resize-ThumbnailPhoto
{
    param(
        [Parameter(Mandatory = $true,
                   Position = 0,
                   ValueFromPipeline = $true)]
        $ImagePath,
        [Parameter(Mandatory = $false)]
        [int]$targetSize = 648,
        [Parameter(Mandatory = $false)]
        [int]$Quality = 85,
        [Parameter(Mandatory = $false)]
        $OutputFile = "$($ImagePath.DirectoryName)\resized\$($ImagePath.BaseName).jpg"
    )
    
    Begin
    {
        Add-Type -AssemblyName "System.Drawing"

        # Get the desired image codec
        # MimeType: image/bmp, image/jpeg, image/gif, image/tiff, image/png
        $Codec = [System.Drawing.Imaging.ImageCodecInfo]::GetImageEncoders() | Where {$_.MimeType -eq 'image/jpeg'}

        #Encoder parameter for image quality
        $ImageEncoder = [System.Drawing.Imaging.Encoder]::Quality
        #create the EncoderParameters object
        $encoderParams = New-Object System.Drawing.Imaging.EncoderParameters(1)
        $encoderParams.Param[0] = New-Object System.Drawing.Imaging.EncoderParameter($ImageEncoder, $Quality)
    }

    Process
    {
        Write-Verbose "Working on - $($ImagePath.FullName)"
        # Initialize an object for the image
        $img = [System.Drawing.Image]::FromFile($($ImagePath.FullName))

        #compute the final ratio to use
        $ratioX = $targetSize / $img.Width;
        $ratioY = $targetSize / $img.Height;
        $ratio = $ratioY
        if ($ratioX -le $ratioY) {
            $ratio = $ratioX
        }

        # Set the new width and height based on the ratio
        $newWidth = [int] ($img.Width * $ratio)
        $newHeight = [int] ($img.Height * $ratio)

        # Create the canvas for resized image and then draw it to fit
        $bmpResized = New-Object System.Drawing.Bitmap($newWidth, $newHeight)
        $graph = [System.Drawing.Graphics]::FromImage($bmpResized)
        $graph.InterpolationMode = [System.Drawing.Drawing2D.InterpolationMode]::HighQualityBicubic
        $graph.Clear([System.Drawing.Color]::White)
        $graph.DrawImage($img, 0, 0, $newWidth, $newHeight)
    }

    End
    {
        Write-Verbose "Saving to - $($OutputFile)"
        #save to file
        $bmpResized.Save($OutputFile, $Codec, $($encoderParams))
        $bmpResized.Dispose()
        $img.Dispose()
    }
}

<#
Get-ChildItem -Path "\\path\to\thumbnailPhotos" -Depth 0 -Filter '*.jpg' | % {
    if ($_.Length -gt 99000) { Resize-ThumbnailPhoto -ImagePath $_ }
}
#>