use BLPConverter.exe from https://github.com/PatrickCyr/BLPConverter

batch_blp_to_png.ps1

param (
    [string]$folderPath,
    [string]$destinationPath = $folderPath,
    [string]$BLPConverter = "BLPConverter.exe"
)

# Check if folderPath is provided
if ([string]::IsNullOrEmpty($folderPath)) {
    Write-Error "Error: folderPath must be provided."
    Write-Host "Usage: script.ps1 -folderPath <FolderPath> [-destinationPath <DestinationPath>] [-BLPConverter <ConverterPath>]"
    exit 1
}

# Check if BLPConverter exists
if (-not (Test-Path -Path $BLPConverter)) {
    Write-Error "Error: BLPConverter not found at the specified path: $BLPConverter"
    exit 1
}

$blpFiles = Get-ChildItem -Path $folderPath -Filter *.blp

foreach ($blpFile in $blpFiles) {
    $blpFilePath = $blpFile.FullName
    $destinationFileName = [System.IO.Path]::ChangeExtension($blpFile.Name, "png")
    $destinationFilePath = Join-Path -Path $destinationPath -ChildPath $destinationFileName
    & $BLPConverter $blpFilePath $destinationFilePath
}