Resizes high-resolution images to appropriate sizes for use in websites

resize.ps1

Add-Type -AssemblyName System.Drawing
# https://gist.github.com/Hashbrown777/fae023538705a1f3f01cd795a2314e61#file-metadata-ps1
. './metadata.ps1'

Filter PointF {
	[System.Drawing.PointF]::new($_[0], $_[1])
}

Function ToArray {
	Begin { $output = [System.Collections.ArrayList]::new() }
	Process { $output.Add($_) | Out-Null }
	End { return ,$output }
}

Function precrop {
	Param(
		$Image,
		[int32]$X = 0,
		[int32]$Y = 0,
		[int32]$Width,
		[int32]$Height,
		[int32]$U = 0,
		[int32]$V = 0
	)
	if ($X -lt 0) {
		$X += $Image.Width
	}
	if ($Y -lt 0) {
		$Y += $Image.Height
	}
	if ($Width) {
		$U = $X + $Width
	}
	else {
		if ($U -lt 1) {
			$U += $Image.Width
		}
		$Width = $U - $X
	}
	if ($Height) {
		$V = $Y + $Height
	}
	else {
		if ($V -lt 1) {
			$V += $Image.Height
		}
		$Height = $V - $Y
	}

	[PSCustomObject]@{
		width  = $Width
		height = $Height
		x      = $X
		y      = $Y
		u      = $U
		v      = $V
	}
}

Function Crop {
	Param(
		[int32]$X = 0,
		[int32]$Y = 0,
		[int32]$Width,
		[int32]$Height,
		[int32]$U = 0,
		[int32]$V = 0
	)
	Process {
		$data = precrop `
			-Image $_ `
			-X $X -Y $Y `
			-Width $Width -Height $Height `
			-U $U -V $V
		$new = New-Object System.Drawing.Bitmap($data.width, $data.height)
		[System.Drawing.Graphics]::FromImage($new).DrawImage(
			$_,
			((0,0),($data.width,0),(0,$data.height) | PointF | ToArray),
			[System.Drawing.RectangleF]::new($data.x, $data.y, $data.u, $data.v),
			[System.Drawing.GraphicsUnit]::Pixel
		)
		$new
	}
}

Function prescale {
	Param(
		$Image,
		$Width,
		$Height,
		$Scale,
		$MinWidth,
		$MinHeight
	)
	Process {
		if ($Width) {
			$Scale = $Width / $Image.Width
		}
		elseif ($Height) {
			$Scale = $Height / $Image.Height
		}
		$Width = $Image.Width * $Scale
		$Height = $Image.Height * $Scale

		if ($Width -lt $MinWidth) {
			$Height = $Image.Height * ($Scale = ($Width = $MinWidth) / $Image.Width)
		}
		if ($Height -lt $MinHeight) {
			$Width = $Image.Width * ($Scale = ($Height = $MinHeight) / $Image.Height)
		}

		[PSCustomObject]@{
			width  = [int32][Math]::Round($Width)
			height = [int32][Math]::Round($Height)
		}
	}
}

Function Scale {
	Param(
		$Width,
		$Height,
		$Scale,
		$MinWidth,
		$MinHeight
	)
	Process {
		$data = prescale `
			-Image $_ `
			-Width $Width `
			-Height $Height
		$new = New-Object System.Drawing.Bitmap($data.width, $data.height)
		[System.Drawing.Graphics]::FromImage($new).DrawImage(
			$_,
			0,
			0,
			$data.width,
			$data.height
		)
		$new
	}
}

Function SaveJPG {
	Param(
		[long]$Quality = 90L,
		$Name,
		[switch]$PassThru
	)
	Begin {
		$encoder = `
			[System.Drawing.Imaging.ImageCodecInfo]::GetImageEncoders() `
			| ?{ $_.FormatDescription -eq 'JPEG' }
		$params = [System.Drawing.Imaging.EncoderParameters]::new(1)
		$params.Param[0] = [System.Drawing.Imaging.EncoderParameter]::new(
			[System.Drawing.Imaging.Encoder]::Quality,
			$Quality
		)
	}
	Process {
		$_.Save($Name, $encoder, $params)
		if ($PassThru) {
			$_
		}
	}
}


Get-ChildItem -Filter '*-56.jpg' -Recurse `
| %{
	$file = $_
	#Destination NSW images are suffixed with -56
	$name = $file.BaseName -replace '-56',''
	$folder = $file.Directory.Parent
	"$folder`t$name"
	$folder = $folder.FullName
	$image = [System.Drawing.Image]::FromFile((Get-Item $file.FullName))
	
	'' + [Math]::Round($file.Length / 1MB, 2) + 'mB'
	''

	$properties = $file | MetaData '^(Tags|Subject|Title|Dimensions)$'
	$properties `
	| Get-Member -Type NoteProperty `
	| %{
		$_.Name,$properties."$($_.Name)" -join "`t"
		''
	}

	#Destination NSW images contain...
	$bottom = $image.Height - 1;
	for (
		$index = 0;
		#...a white field with black text (grey pixels)...
		$image.GetPixel(200, $bottom).Name -match '^..(..)\1\1$' -and
		$image.GetPixel(400, $bottom).Name -match '^..(..)\1\1$' -and
		$image.GetPixel(600, $bottom).Name -match '^..(..)\1\1$';
		#...starting at 543px in height +50n
		#where n is the number of extra lines in the description
		$bottom -= @(50,543)[!$index++]
	) {}
	"Cropping out $($image.Height - $bottom)px footer",''
	$image = $image `
	| Crop -V $bottom `
	| SaveJPG `
		-Quality 95L `
		-Name "$folder/_original/$name.jpg" `
		-PassThru

	$scale = prescale -Image $image -Width 1920 -MinHeight 720
	"Scaling to 1920x$($scale.height)"
	$file = "$folder/$name.jpg"
	$image `
	| Scale -Width 1920 -MinHeight 720 `
	| SaveJPG -Name $file
	'' + [Math]::Round((gci $file).Length / 1MB, 2) + 'mB'
	''

	if ($scale.Height -gt 720) {
		$scale = prescale -Image $image -Height 720 -MinWidth 768
		"Mobile scaling to $($scale.width)x720"
		$file = "$folder/mobile-$name.jpg"
		$image `
		| Scale -Height 720 -MinWidth 768 `
		| SaveJPG -Name $file
		'' + [Math]::Round((gci $file).Length / 1MB, 2) + 'mB'
		''
	}

	''
} `
| Tee 'carousel.txt'