Add optional -Target parameter to Create-Turnaround.ps1 that defaults to '<last directory member>.jpg' in current directory, deriving name from source directory when -Source is a directory or from current directory when -Source is a file pattern, with drive root detection that throws an error for paths like 'C:\' that have no directory member to name the file after

Create-Turnaround.ps1

@@ -12,6 +12,10 @@
 .PARAMETER Target
     Path to the output turnaround image. Can be absolute or relative to current directory. .png extension is added if not provided.
     A recognised image extension (.png, .jpg, .jpeg, .webp, .bmp, .avif, .tif, .tiff) selects the output format.
+    When omitted, a JPEG named after the last directory member of the source is written to the current directory:
+    - -Source is a directory: the last directory member of that directory's full path (e.g. C:\renders\CharacterA -> CharacterA.jpg).
+    - -Source is a file pattern or a single file: the last directory member of the current directory's full path.
+    Throws when that path is a drive root (e.g. C:\), since it has no directory member to name the file after.
 .PARAMETER Rows
     Number of rows to arrange the images in. Defaults to 1 (all images in a single horizontal row).
     When only -Rows is given, the number of columns is computed as ceil(imageCount / Rows).
@@ -53,8 +57,8 @@ param(
     [Parameter(Mandatory = $true)]
     [string]$Source,
 
-    [Parameter(Mandatory = $true)]
+    [Parameter(Mandatory = $false)]
-    [string]$Target,
+    [string]$Target = $null,
 
     [Parameter(Mandatory = $false)]
     [int]$Rows = 0,
@@ -105,6 +109,31 @@ function Get-ImageDimensions {
     return [pscustomobject]@{ Width = [int]$Matches[1]; Height = [int]$Matches[2] }
 }
 
+# --- Default -Target: '<last directory member>.jpg' in the current directory ---
+# The name comes from the source directory when -Source is a directory, and from the
+# current directory when -Source is a file pattern or a single file. Either way the file
+# is written to the current directory.
+if ([string]::IsNullOrWhiteSpace($Target)) {
+    if (Test-Path -LiteralPath $Source -PathType Container) {
+        $nameSourcePath = (Resolve-Path -LiteralPath $Source).Path
+    } else {
+        $nameSourcePath = (Get-Location).Path
+    }
+
+    $nameSourcePath = [System.IO.Path]::GetFullPath($nameSourcePath)
+    $trimmedPath = $nameSourcePath.TrimEnd('\', '/')
+    $nameLeaf = Split-Path -Path $trimmedPath -Leaf
+
+    # 'C:\' trims to 'C:', which has no directory member to name the file after.
+    if ([string]::IsNullOrWhiteSpace($nameLeaf) -or $trimmedPath -match '^[A-Za-z]:$') {
+        Write-Error ('Cannot derive a target file name from ''{0}'': the path is a drive root with no directory member. Specify -Target explicitly.' -f $nameSourcePath)
+        exit 1
+    }
+
+    $Target = Join-Path (Get-Location).Path ('{0}.jpg' -f $nameLeaf)
+    Write-Host ('No -Target specified; using {0}' -f $Target)
+}
+
 # --- Resolve -Target and the output format ---
 $TargetPath = $Target
 $targetExt = [System.IO.Path]::GetExtension($TargetPath).ToLowerInvariant()