Word compresses images

[vnagel]

Word compresses images by default. This results in not maintaining the original OneNote image quality.

I was successfully able to turn off image compression in Word for the conversion script by updating the relevant setting via the registry. Note that the registry key path could vary by Word version (I'll include a comment below with a more generic script that handles this).

Set-ItemProperty -Path "HKCU:\Software\Microsoft\Office\16.0\Word\Options" `
                 -Name "AutomaticPictureCompressionDefault" `
                 -Type DWord -Value 0

I confirmed that this causes the "Do not compress images in file" setting in the generated docx file to be checked, and the resulting image resolution to be what's expected (or at least larger than the compressed version).

Note that if "Do not compress images in file" is checked, the "Default resolution" setting doesn't matter. If you want to enable compression but change the default resolution, you could try setting AutomaticPictureCompressionDefault to 1 and modifying the ExportBitmapResolution registry value.

I tried just updating the compression setting via Word's GUI located at File > Options > Advanced (see pic below), but even though I selected "All New Documents", Word docs created via the conversion script still had the default compression settings (confirmed by checking the setting in the generated docx file - not shown in pic below) and the resulting image resolution indicated compression occurred.

*Note that you can't interact with the settings unless you have a document open.

[vnagel]

Here's a more generic script to disable image compression. Yes, I used ChatGPT :)

EDIT: I realized that, since this project requires Microsoft Word >= 2016, the path should always be the same ("HKCU:\Software\Microsoft\Office\<version>\Word\Options" where <version> is always 16.0 for Office 2016/2019/365. But, I guess making it generic might still be valuable to help prevent breaking if word version is bumped.

EDIT 2: Also, the if ($null -eq $currentVal) check below is probably not a good idea in case it hasn't been set yet. That's an artifact of my investigation.

# Create a COM object to detect Word version
try {
    $word = New-Object -ComObject Word.Application -ErrorAction Stop
    $wordVersion = $word.Version
    Write-Host "Detected Word version: $wordVersion"
}
catch {
    Write-Warning "Unable to launch Word. Ensure Word is installed. Aborting."
    return
}
finally {
    if ($null -ne $word) {
        $word.Quit()
        [System.Runtime.InteropServices.Marshal]::ReleaseComObject($word) | Out-Null
    }
}

# Parse out major version number (e.g., '16' from '16.0')
$majorVersion = ($wordVersion -split '\.')[0]

# Construct registry path
$keyPath  = "HKCU:\Software\Microsoft\Office\$($majorVersion).0\Word\Options"
$valueName = "AutomaticPictureCompressionDefault"

Write-Host "Using registry path: $keyPath"

# Check if registry path exists
if (Test-Path $keyPath) {
    # Try to get the current value
    $currentVal = (Get-ItemProperty -Path $keyPath -Name $valueName -ErrorAction SilentlyContinue).$valueName
    
    if ($null -eq $currentVal) {
        Write-Host "Registry key exists, but '$valueName' not found under '$keyPath'."
    }
    else {
        Write-Host "Current value of '$valueName' is '$currentVal'."
        
        # Example: If it's not 0, set it to 0
        if ($currentVal -ne 0) {
            Write-Host "Setting $valueName to 0 (disable image compression)."
            Set-ItemProperty -Path $keyPath -Name $valueName -Type DWord -Value 0
            Write-Host "Set $valueName = 0 in $keyPath."
        }
        else {
            Write-Host "$valueName is already set to 0."
        }
    }
}
else {
    Write-Warning "Registry path '$keyPath' does NOT exist. Not creating or modifying the key."
}

Write-Host "Done."

[vnagel]

Optimally, I think the conversion script should disable compression by default and allow configuring it via config.ps1.

[leojonathanoh]

Thanks for the bug report. This is a nice finding. Word should not be mutating images, since want a complete conversion.

It could be a newly introduced setting in newer Word versions (past few years). First, we will need other users to confirm the GUI setting fix to disable compression works across various Word versions, and also confirm the associated registry key and their Word version, before adding the fix as part of the script. This is to be safe so we don’t modify registry keys wrongly.

[vnagel]

Sounds good. Just to clarify, when I updated the setting via the Word GUI, it did not persist for the word docs created with the conversion script. Only the registry update worked for me.

Also, I suspect Word could have been compressing images by default since Word 2016 based on this article: https://support.microsoft.com/en-us/office/turn-off-picture-compression-81a6b603-0266-4451-b08e-fc1bf58da658

Applies To: Excel for Microsoft 365 Word for Microsoft 365 Outlook for Microsoft 365 PowerPoint for Microsoft 365 Excel 2024 Outlook 2024 PowerPoint 2024 Excel 2021 Word 2021 Outlook 2021 PowerPoint 2021 Excel 2019 Word 2019 Outlook 2019 PowerPoint 2019 Excel 2016 Word 2016 Outlook 2016 PowerPoint 2016

Though maybe it was only more recent versions where compression was enabled by default.

[leojonathanoh]

Good information. It seems like a fix worth implementing soon.