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<#
.SYNOPSIS
Resize an image
.DESCRIPTION
Resize an image based on a new given height or width or a single dimension and a maintain ratio flag.
The execution of this CmdLet creates a new file named "OriginalName_resized" and maintains the original
file extension
.PARAMETER Width
The new width of the image. Can be given alone with the MaintainRatio flag
.PARAMETER Height
The new height of the image. Can be given alone with the MaintainRatio flag
.PARAMETER ImagePath
The path to the image being resized
.PARAMETER MaintainRatio
Maintain the ratio of the image by setting either width or height. Setting both width and height and also this parameter
results in an error
.PARAMETER Percentage
Resize the image *to* the size given in this parameter. It's imperative to know that this does not resize by the percentage but to the percentage of
the image.
.PARAMETER SmoothingMode
Sets the smoothing mode. Default is HighQuality.
.PARAMETER InterpolationMode
Sets the interpolation mode. Default is HighQualityBicubic.
.PARAMETER PixelOffsetMode
Sets the pixel offset mode. Default is HighQuality.
.EXAMPLE
Resize-Image -Height 45 -Width 45 -ImagePath "Path/to/image.jpg"
.EXAMPLE
Resize-Image -Height 45 -MaintainRatio -ImagePath "Path/to/image.jpg"
.EXAMPLE
#Resize to 50% of the given image
Resize-Image -Percentage 50 -ImagePath "Path/to/image.jpg"
.NOTES
Written By:
Christopher Walker
#>
Function Resize-Image() {
[CmdLetBinding(
SupportsShouldProcess=$true,
PositionalBinding=$false,
ConfirmImpact="Medium",
DefaultParameterSetName="Absolute"
)]
Param (
[Parameter(Mandatory=$True)]
[ValidateScript({
$_ | ForEach-Object {
Test-Path $_
}
})][String[]]$ImagePath,
[Parameter(Mandatory=$False)][Switch]$MaintainRatio,
[Parameter(Mandatory=$False, ParameterSetName="Absolute")][Int]$Height,
[Parameter(Mandatory=$False, ParameterSetName="Absolute")][Int]$Width,
[Parameter(Mandatory=$False, ParameterSetName="Percent")][Double]$Percentage,
[Parameter(Mandatory=$False)][System.Drawing.Drawing2D.SmoothingMode]$SmoothingMode = "HighQuality",
[Parameter(Mandatory=$False)][System.Drawing.Drawing2D.InterpolationMode]$InterpolationMode = "HighQualityBicubic",
[Parameter(Mandatory=$False)][System.Drawing.Drawing2D.PixelOffsetMode]$PixelOffsetMode = "HighQuality",
[Parameter(Mandatory=$False)][String]$NameModifier = "resized"
)
Begin {
If ($Width -and $Height -and $MaintainRatio) {
Throw "Absolute Width and Height cannot be given with the MaintainRatio parameter."
}
If (($Width -xor $Height) -and (-not $MaintainRatio)) {
Throw "MaintainRatio must be set with incomplete size parameters (Missing height or width without MaintainRatio)"
}
If ($Percentage -and $MaintainRatio) {
Write-Warning "The MaintainRatio flag while using the Percentage parameter does nothing"
}
}
Process {
ForEach ($Image in $ImagePath) {
$Path = (Resolve-Path $Image).Path
$Dot = $Path.LastIndexOf(".")
#Add name modifier (OriginalName_{$NameModifier}.jpg)
$OutputPath = $Path.Substring(0,$Dot) + "_" + $NameModifier + $Path.Substring($Dot,$Path.Length - $Dot)
$OldImage = New-Object -TypeName System.Drawing.Bitmap -ArgumentList $Path
# Grab these for use in calculations below.
$OldHeight = $OldImage.Height
$OldWidth = $OldImage.Width
If ($MaintainRatio) {
$OldHeight = $OldImage.Height
$OldWidth = $OldImage.Width
If ($Height) {
$Width = $OldWidth / $OldHeight * $Height
}
If ($Width) {
$Height = $OldHeight / $OldWidth * $Width
}
}
If ($Percentage) {
$Product = ($Percentage / 100)
$Height = $OldHeight * $Product
$Width = $OldWidth * $Product
}
$Bitmap = New-Object -TypeName System.Drawing.Bitmap -ArgumentList $Width, $Height
$NewImage = [System.Drawing.Graphics]::FromImage($Bitmap)
#Retrieving the best quality possible
$NewImage.SmoothingMode = $SmoothingMode
$NewImage.InterpolationMode = $InterpolationMode
$NewImage.PixelOffsetMode = $PixelOffsetMode
$NewImage.DrawImage($OldImage, $(New-Object -TypeName System.Drawing.Rectangle -ArgumentList 0, 0, $Width, $Height))
If ($PSCmdlet.ShouldProcess("Resized image based on $Path", "save to $OutputPath")) {
$Bitmap.Save($OutputPath)
}
$Bitmap.Dispose()
$NewImage.Dispose()
$OldImage.Dispose()
}
}
}
@someshinyobject

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Owner Author

commented Dec 31, 2017

Fixed an issue with the percentage variable.

@adbertram

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commented Sep 30, 2018

Thanks for this function! I'm including it in an upcoming TechSnips.io video I'm doing. You may want to include Add-Type -AssemblyName 'System.Drawing' though. It won't work without it loaded.

Good work on this. Feel free to join us if you'd like. ;) https://www.techsnips.io/join-us

@piers7

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commented Oct 15, 2018

I tried this on a bunch of JPEGs at 50%, but whilst the pixel sizes were halved, the file sizes all went up! Think there is a quality setting you need to expose somewhere.

@jonathancounihan

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commented May 21, 2019

@piers7, You must save the file as a jpeg, the default value is png.

ie use

    $Bitmap.Save($OutputPath, [System.Drawing.Imaging.ImageFormat]::Jpeg)
@kirillito

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commented Jul 19, 2019

Probably worth to add $OldImage.Dispose() next to

            $Bitmap.Dispose()
            $NewImage.Dispose()

to release original files.

@someshinyobject

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commented Jul 30, 2019

@Kirill Yea that's a great idea! Thanks. Updated the gist.

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