Create a multi-layer ICO file from multiple source images using FFmpeg #powershell #ffmpeg #favicon

New-MultiLayerIcon.ps1

<#
.SYNOPSIS
    Creates a multi-layer ICO file from multiple source images using FFmpeg.

.DESCRIPTION
    Combines individual image assets into a single ICO container. Supports piping 
    file objects or paths directly into the script. Dynamically maps inputs 
    to ensure all layers are included in the final mux.

.PARAMETER OutputPath
    The destination path for the generated .ico file. Defaults to 'favicon.ico'.

.PARAMETER SourceFiles
    An array of file paths to be used as icon layers. Supports pipeline input.
    Mandatory for the build process.

.PARAMETER Help
    Displays this help message and exits without processing.
    Aliases: -h

.EXAMPLE
    .\New-MultiLayerIcon.ps1 -SourceFiles "16.png", "32.png" -OutputPath "App.ico"

.EXAMPLE
    Get-ChildItem .\Assets\*.png | .\New-MultiLayerIcon.ps1 -OutputPath "Bundle.ico"

.EXAMPLE
    .\New-MultiLayerIcon.ps1 -Help
#>
[CmdletBinding(DefaultParameterSetName = 'Build')]
param(
    [Parameter(
        Position = 0, 
        ParameterSetName = 'Build'
    )]
    [string]$OutputPath = "favicon.ico",

    [Parameter(
        Position = 1, 
        Mandatory = $true, 
        ValueFromPipeline = $true, 
        ValueFromPipelineByPropertyName = $true,
        ParameterSetName = 'Build'
    )]
    [Alias("FullName", "Path")]
    [string[]]$SourceFiles,

    [Parameter(ParameterSetName = 'Help')]
    [Alias('h')]
    [Switch]$Help
)

begin {
    # Check for Help switch immediately to bypass dependency checks
    if ($Help) {
        # Retrieve the path to this executing script and invoke Get-Help on it
        Get-Help $MyInvocation.MyCommand.Path -Detailed
        return # Exit the Begin block (and effectively the script)
    }

    Write-Verbose "Initializing Icon Build Process..."
    
    # Check for FFmpeg dependency
    if (-not (Get-Command ffmpeg -ErrorAction SilentlyContinue)) {
        Write-Error "FFmpeg was not found in the system PATH. Please install it to continue."
        break
    }

    # Internal list to collect piped or array-based inputs
    $InputList = New-Object System.Collections.Generic.List[string]
}

process {
    # If we are in Help mode, skip processing
    if ($Help) { return }

    # Collect inputs from the pipeline or the parameter array
    foreach ($File in $SourceFiles) {
        $Item = Get-Item $File -ErrorAction SilentlyContinue
        if ($Item) {
            $InputList.Add($Item.FullName)
            Write-Verbose "Added layer: $($Item.FullName)"
        } else {
            Write-Warning "File not found and skipped: $File"
        }
    }
}

end {
    # If we are in Help mode, exit gracefully
    if ($Help) { return }

    if ($InputList.Count -eq 0) {
        Write-Error "No valid source files were provided."
        return
    }

    Write-Host "Processing $($InputList.Count) layers into $OutputPath..." -ForegroundColor Cyan

    # Dynamically build FFmpeg arguments
    $FFmpegArgs = New-Object System.Collections.Generic.List[string]

    # 1. Add Input Flags
    foreach ($Path in $InputList) {
        $FFmpegArgs.Add("-i")
        $FFmpegArgs.Add($Path)
    }

    # 2. Add Mapping Flags (Stream #0:0, #1:0, etc.)
    for ($i = 0; $i -lt $InputList.Count; $i++) {
        $FFmpegArgs.Add("-map")
        $FFmpegArgs.Add("$($i):0")
    }

    # 3. Add Output and Overwrite
    $FFmpegArgs.Add("-y")
    $FFmpegArgs.Add($OutputPath)

    try {
        # Execute FFmpeg with the dynamic argument list
        $ProcessParams = @{
            FilePath     = "ffmpeg"
            ArgumentList = $FFmpegArgs
            Wait         = $true
            NoNewWindow  = $true
        }
        
        Start-Process @ProcessParams

        if (Test-Path $OutputPath) {
            $FileItem = Get-Item $OutputPath
            $SizeKB = [Math]::Round($FileItem.Length / 1KB, 2)
            Write-Host "Build Complete: $OutputPath ($SizeKB KB)" -ForegroundColor Green
        }
    }
    catch {
        Write-Error "FFmpeg execution failed: $($_.Exception.Message)"
    }
}