Converts image file supported by GDI+ to an ASCII representation.

i2a.ps1

#TODO: Add support for URIs

function Convert-ImageToAscii {
    [Alias('i2a')]
    [OutputType([string])]
    [CmdletBinding()]
    param(
        [Parameter(Mandatory, Position = 0, ValueFromPipeline)]
        [ValidateScript({ $PSItem.Exists -and
            $PSItem.Extension -in '.bmp', '.gif', '.jpeg', '.jpg', '.png', '.tiff' })]
        [System.IO.FileInfo]
        $Path,

        [Parameter(Position = 1)]
        [ValidateSet('Low', 'Mid', 'High')]
        [string]
        $Resolution = 'Low',

        [Parameter(Mandatory, ParameterSetName = 'SetDimensionsManually')]
        [ValidateRange(1, [int]::MaxValue)]
        [int]
        $Width,

        [Parameter(Mandatory, ParameterSetName = 'SetDimensionsManually')]
        [ValidateRange(1, [int]::MaxValue)]
        [int]
        $Height,

        [Parameter(ParameterSetName = 'SetDimensionsAutomatically')]
        [switch]
        $FitConsoleHeight,

        [switch]
        $Invert
    )

    begin {
        try {
            & {
                $ErrorActionPreference = 'Stop'
                [void][Drawing.Image]
            }
        }
        catch {
            Add-Type -AssemblyName System.Drawing
        }

        $symbols = $(if ($Invert.IsPresent) {
            @{
                Low  = '@#+. '
                Mid  = '@%#*+:,. '
                High = '@%#omCXxt?+~;:,. '
            }
        }
        else {
            @{
                Low  = ' .+#@'
                Mid  = ' .,:+*#%@'
                High = ' .,:;~+?txXCmo#%@'
            }
        })[$Resolution]
    }

    process {
        try {
            $img = [Drawing.Image]::FromFile($Path.FullName)

            [int]$w, [int]$h = switch ($PSCmdlet.ParameterSetName) {
                SetDimensionsManually {
                    ($Width / 2), $Height
                }

                SetDimensionsAutomatically {
                    @(($Host.UI.RawUI.WindowSize.Height * ($img.Width / $img.Height))
                      ($Host.UI.RawUI.WindowSize.Height - 4))
                }

                default {
                    @(($Host.UI.RawUI.WindowSize.Width / 2 - 1)
                      ($Host.UI.RawUI.WindowSize.Width / 2 / ($img.Width / $img.Height)))
                }
            }

            $bmp = [Drawing.Bitmap]::new($w, $h)
            $bmp.SetResolution($img.HorizontalResolution, $img.VerticalResolution)

            $graphics                    = [Drawing.Graphics]::FromImage($bmp)
            $graphics.CompositingMode    = [Drawing.Drawing2D.CompositingMode]::SourceCopy
            $graphics.CompositingQuality = [Drawing.Drawing2D.CompositingQuality]::HighQuality
            $graphics.InterpolationMode  = [Drawing.Drawing2D.InterpolationMode]::HighQualityBicubic
            $graphics.SmoothingMode      = [Drawing.Drawing2D.SmoothingMode]::HighQuality
            $graphics.PixelOffsetMode    = [Drawing.Drawing2D.PixelOffsetMode]::HighQuality

            $rec = [Drawing.Rectangle]::new(0, 0, $w, $h)
            $wrapMode = [Drawing.Imaging.ImageAttributes]::new()
            $wrapMode.SetWrapMode([Drawing.Drawing2D.WrapMode]::TileFlipXY)
            $graphics.DrawImage($img, $rec, 0, 0, $img.Width, $img.Height, [Drawing.GraphicsUnit]::Pixel, $wrapMode)

            -join $(foreach ($y in 0..($bmp.Height-1)) {
                foreach ($x in 0..($bmp.Width-1)) {
                    $p = $bmp.GetPixel($x, $y)
                    "$($symbols[[Math]::Floor((($p.R+$p.G+$p.B)/3)/(256/$symbols.Length))])" * 2
                }
                "`n"
            })
        }
        finally {
            if ($null -ne $wrapMode) { $wrapMode.Dispose() }
            if ($null -ne $graphics) { $graphics.Dispose() }
            if ($null -ne $bmp)      { $bmp.Dispose() }
            if ($null -ne $img)      { $img.Dispose() }
        }
    }

    <#
        .SYNOPSIS
            Convert image to ascii.

        .DESCRIPTION
            Convert any image to ascii picture by representing each pixels grayscale value as an ascii character.
            The higher the grayscale value the more space the corresponding ascii character fills. Before being
            processed the image will be cropped in memory to fit the consoles width or height.

        .PARAMETER Path
            The path to the image to process.

        .PARAMETER Resolution
            The amount of different ascii characters the grayscale values will be assigned to. The bigger the
            console window and the smaller the font size a higher resolution tends to look better when the image
            is also of high resolution.

        .PARAMETER Width
            Set the width of the output ascii picture manually.

        .PARAMETER Height
            Set the height of the output ascii picture manually.

        .PARAMETER FitConsoleHeight
            Whether the output ascii picture should fit the console height instead of width. Only applicable if
            width and height are not explicitly specified.

        .PARAMETER Invert
            Whether the output ascii picture should be inverted. Use this on light console backgrounds
            for better results.

        .INPUTS
            System.IO.FileInfo
            System.String
            System.Int32

        .OUTPUTS
            System.String

        .COMPONENT
            GDI+

        .EXAMPLE
            Convert-ImageToAscii C:\Users\Bobby\Pictures\bobby-fischer.jpg

        .EXAMPLE
            Convert-ImageToAscii -Path C:\Users\Bobby\Pictures\bobby-fischer.jpg -Resolution Mid -FitConsoleHeight

        .EXAMPLE
            Convert-ImageToAscii -Path C:\Users\Bobby\Pictures\bobby-fischer.jpg -Width 120 -Height 80 -Invert
    #>
}