如何用PowerShell拆分并重新写入.tif文件的IPTC关键词？

Got it, let's get those messed-up TIFF keywords sorted out! PowerShell doesn't have native, out-of-the-box support for IPTC metadata, but we've got two solid approaches here—one using a reliable third-party tool (my go-to) and another using .NET classes if you want to avoid external tools.

Option 1: Use ExifTool (Recommended) #

ExifTool is a powerful, free metadata editor that handles IPTC (and pretty much every other metadata standard) flawlessly. It's way simpler than rolling your own solution with .NET.

Step 1: Install ExifTool #

• If you use Chocolatey, run this in an elevated PowerShell window:

  choco install exiftool
  

• Alternatively, download the standalone executable from the official site, extract it, and add its folder to your system PATH (or just use the full path to exiftool.exe in the script below).

Step 2: PowerShell Script to Split and Re-Write Keywords #

This script will loop through all TIFFs in your target folder, split the merged keyword string, and write them back as individual IPTC keywords.

# Replace with your TIFF folder path
$targetFolder = "C:\Your\TIFF\Folder\Path"
# Set the delimiter that's separating your merged keywords (e.g., ", ", "; ", " | ")
$keywordDelimiter = ", "

# Grab all TIFF files in the folder
$tiffFiles = Get-ChildItem -Path $targetFolder -Filter "*.tif" -File

foreach ($file in $tiffFiles) {
    Write-Host "Processing: $($file.Name)"

    # Read the current merged keyword string from IPTC
    $currentKeywords = & exiftool -s3 -Keywords $file.FullName

    if (-not [string]::IsNullOrEmpty($currentKeywords)) {
        # Split the string, trim whitespace, and filter out empty entries
        $splitKeywords = $currentKeywords -split $keywordDelimiter | ForEach-Object { $_.Trim() } | Where-Object { $_ }

        if ($splitKeywords.Count -gt 0) {
            # Write the split keywords back to the file (ExifTool auto handles IPTC multi-keyword format)
            & exiftool "-Keywords=$($splitKeywords -join ', ')" $file.FullName

            # Clean up the backup file ExifTool creates (remove this line if you want to keep backups!)
            Remove-Item -Path "$($file.FullName)_original" -Force -ErrorAction SilentlyContinue

            Write-Host "✅ Updated keywords for $($file.Name)"
        } else {
            Write-Host "⚠️ No valid keywords left after splitting for $($file.Name)"
        }
    } else {
        Write-Host "ℹ️ No keywords found in $($file.Name)"
    }
}

Write-Host "`nProcessing finished!"

Key Notes: #

• Adjust $keywordDelimiter to match whatever character(s) are separating your merged keywords (common ones are commas, semicolons, or pipes).
• ExifTool creates a backup file by default (e.g., image.tif_original). The script deletes it automatically, but you can remove that Remove-Item line if you want to keep backups.

Option 2: Use .NET's System.Drawing (No External Tools) #

If you prefer not to install third-party software, you can use .NET's built-in imaging classes. This is more complex and has some caveats (like handling encoding inconsistencies), but it works for basic cases.

Add-Type -AssemblyName System.Drawing

$targetFolder = "C:\Your\TIFF\Folder\Path"
$keywordDelimiter = ", "

$tiffFiles = Get-ChildItem -Path $targetFolder -Filter "*.tif" -File

foreach ($file in $tiffFiles) {
    Write-Host "Processing: $($file.Name)"
    $bitmap = [System.Drawing.Bitmap]::FromFile($file.FullName)
    
    try {
        # Find the existing IPTC Keywords property (ID 0x0250)
        $existingKeywordItems = $bitmap.PropertyItems | Where-Object { $_.Id -eq 0x0250 }

        if ($existingKeywordItems) {
            # Decode the merged keyword string (assumes UTF-8 encoding; adjust if needed)
            $currentKeywords = [System.Text.Encoding]::UTF8.GetString($existingKeywordItems[0].Value).TrimEnd([char]0)
            
            if (-not [string]::IsNullOrEmpty($currentKeywords)) {
                $splitKeywords = $currentKeywords -split $keywordDelimiter | ForEach-Object { $_.Trim() } | Where-Object { $_ }
                
                if ($splitKeywords.Count -gt 0) {
                    # Keep all non-keyword metadata properties
                    $nonKeywordItems = $bitmap.PropertyItems | Where-Object { $_.Id -ne 0x0250 }
                    $newPropertyItems = $nonKeywordItems.Clone()

                    # Add each split keyword as a separate IPTC entry
                    foreach ($kw in $splitKeywords) {
                        $newItem = $bitmap.PropertyItems[0].Clone()
                        $newItem.Id = 0x0250
                        $newItem.Type = 2 # String data type
                        $kwBytes = [System.Text.Encoding]::UTF8.GetBytes($kw + [char]0)
                        $newItem.Value = $kwBytes
                        $newItem.Len = $kwBytes.Length
                        $newPropertyItems += $newItem
                    }

                    # Apply the updated metadata and save the file
                    $bitmap.SetPropertyItems($newPropertyItems)
                    $bitmap.Save($file.FullName, [System.Drawing.Imaging.ImageFormat]::Tiff)
                    Write-Host "✅ Updated keywords for $($file.Name)"
                } else {
                    Write-Host "⚠️ No valid keywords left after splitting for $($file.Name)"
                }
            } else {
                Write-Host "ℹ️ No keywords found in $($file.Name)"
            }
        } else {
            Write-Host "ℹ️ No IPTC Keywords property exists in $($file.Name)"
        }
    } finally {
        # Always dispose the bitmap to free up resources
        $bitmap.Dispose()
    }
}

Write-Host "`nProcessing finished!"

Caveats for the .NET Approach: #

• Encoding can be hit-or-miss: Some TIFFs might use ASCII instead of UTF-8 for IPTC data. If you see garbled text, replace [System.Text.Encoding]::UTF8 with [System.Text.Encoding]::ASCII.
• This might overwrite other TIFF metadata if not handled carefully, whereas ExifTool preserves all other metadata by default.

内容的提问来源于stack exchange，提问作者Rico Komenda