[UDF] IWICImagingFactory: Manipulate Image Metadata (Read/Write, Object-Oriented Approach)

[Numeric1]

 

Hello everyone,

I'm pleased to share a UDF I developed to work with IWICImagingFactory from the Windows Imaging Component (WIC), focused exclusively on reading and writing image metadata.

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🔍 Why this UDF?

IWICImagingFactory is a powerful API but can also be particularly confusing when working with metadata. Its layers of abstraction, data formats, and interface complexity can easily distract you from your goals without a clear structure.

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🧩 Key Features:

• 🔄 Read and write metadata using WIC interfaces (IWICMetadataQueryReader, IWICMetadataQueryWriter)

• 💾 Supports common formats (JPEG, PNG, TIFF, etc.)

• 🧠 Built using an object-oriented model via AutoItObject to encapsulate complexity and avoid side effects

• ⚠️ Full support for PROPVARIANT and VARIANT types, essential for COM interaction

• 🔗 Handles the WIC metadata query language (e.g., /app1/ifd/exif:{ushort=36867} for Date Taken)

• 📜 Works with WIC-compliant hierarchical metadata queries

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🧠 Prerequisites / Recommended Knowledge

• Solid understanding of COM programming in AutoIt

• Familiarity with PROPVARIANT/VARIANT (types, conversion, init/cleanup)

• Knowledge of WIC metadata schema and hierarchy

• Comfortable with object-oriented programming in AutoIt (using AutoItObject)

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🧪 Why use an object-oriented approach?

IWICImagingFactory is as flexible as it is tricky. Exploring it directly can lead to unexpected behaviors or technical detours.
The object-oriented approach helps contain this complexity, structure features properly, and avoid common pitfalls when dealing with raw COM interfaces.

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📁 What’s Included in the UDF

• A main object WICImageMeta (or similar) that encapsulates the image, reader/writer, and associated interfaces

• Straightforward methods like .ReadMeta($sPath), .WriteMeta($sPath, $vValue, $sType), .Save($sDest), etc.

• Automatic resource management (Release, Cleanup)

• Examples for reading/writing EXIF, XMP, and other metadata

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📷 Quick Usage Example

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#include <MsgBoxConstants.au3>
#include <WinAPI.au3>
#include <Array.au3>
#include "IWICImagingMetadata.au3" ; This is your custom UDF for WIC metadata

; Path to a test image (replace with your own file path)
Local $sFilename = @DesktopDir & "\screenshot.png"

; === 1. Create the WIC Imaging Factory ===
; This is the entry point for all WIC operations
Local $oFactory = _WIC_ImagingFactory()
If Not IsObj($oFactory) Then
    MsgBox(0, "Error", "Failed to create WIC Imaging Factory")
    Exit
EndIf

; === 2. Create a decoder from the image file ===
; This will analyze the image format and prepare for frame extraction
Local $oDecoder = $oFactory.createDecoderFromFileName($sFilename)
If Not IsObj($oDecoder) Then
    MsgBox(0, "Error", "Failed to create image decoder: @error=" & @error)
    $oFactory = 0
    Exit
EndIf

; === 3. Get the first frame of the image ===
; Most still images have a single frame; this retrieves it from the decoder
Local $oFrame = $oFactory.createBitmapFrameDecode($oDecoder)
If Not IsObj($oFrame) Then
    MsgBox($MB_ICONERROR, "Error", "Failed to retrieve image frame: @error=" & @error)
    $oDecoder = 0
    $oFactory = 0
    Exit
EndIf

; === 4. Get a metadata query reader from the frame ===
; This reader allows you to query metadata values using WIC metadata paths
Local $oQueryReader = $oFactory.getMetadataQueryReader($oFrame)
If Not IsObj($oQueryReader) Then
    MsgBox(0, "Error", "Failed to get metadata query reader: @error=" & @error)
    $oFrame = 0
    $oDecoder = 0
    $oFactory = 0
    Exit
EndIf

; === 5. Enumerate available metadata names ===
; This step is crucial to explore what metadata is actually present.
; It returns an array of metadata query paths that can be used.
Local $aNames = $oFactory.enumerateMetaDataNames($oQueryReader)
If @error Then
    ConsoleWrite("Error: Failed to enumerate metadata names: @error=" & @error & @CRLF)
Else
    ConsoleWrite("Available metadata names: " & _ArrayToString($aNames, "|") & @CRLF)
EndIf

; === 6. Read a specific metadata value ===
; In this case, we're trying to read a textual field: "Creation Time" in a PNG tEXt chunk
Local $sQuery = "/tEXt/{str=Creation Time}"
Local $vData = $oFactory.queryMetadataByName($oQueryReader, $sQuery)

If Not @error Then
    ConsoleWrite("Metadata read: " & $sQuery & " = " & $vData & @CRLF)
Else
    ConsoleWrite("Error: Failed to read " & $sQuery & " : @error=" & @error & @CRLF)
EndIf

; === NOTE ===
; If your query selects a metadata **block**, then `vData` may be another IWICMetadataQueryReader object.
; In that case, you must call `queryMetadataByName` again, passing this sub-reader to reach nested values.

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💬 Conclusion

If you've worked with image metadata using WIC before, you know it's a technical challenge.
This UDF aims to simplify the process while preserving full control for those who need fine-grained access.

Feel free to try it out, give feedback, or suggest improvements.
Enjoy digging into the hidden data of your images! 📸

 

 

IWICImagingMetadata.au3