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POHow do I use the WIC API to read/write custom EXIF data?
 

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  1. POHow do I use the WIC API to read/write custom EXIF data?
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    <p>I have gone through the documentation at: <a href="http://msdn.microsoft.com/en-us/library/windows/desktop/ee719799(v=vs.85).aspx" rel="nofollow">http://msdn.microsoft.com/en-us/library/windows/desktop/ee719799(v=vs.85).aspx</a></p> <p>As context, I am trying to encode in the JPEG-XR format and I want to emulate GDI+'s <code>SetPropertyItem</code>, <code>GetPropertyItem</code> functionality.</p> <p>I basically have 3 questions:</p> <ol> <li>If I want to add a custom property to the exif header what is the correct query path?</li> <li>Can I use a custom ID, say <code>{ushort=1111}</code> to identify it and how do I verify if an ID is already defined?</li> <li>Is this the same as the <code>id</code> field of GdiPlus::PropertyItem?</li> </ol> <p>For example, is the following valid:</p> <pre><code>PROPVARIANT value; value.vt = VT_LPWSTR; value.pwszVal= L"Metadata Test"; hr = piFrameQWriter-&gt;SetMetadataByName(L"/ifd/exif/{ushort=1111}"); </code></pre> <p>This code block succeeds, but when I try to read back the same metadata using:</p> <pre><code>IWICMetadataQueryReader *pQueryReader = NULL; if(SUCCEEDED(hr)) { hr = piFrame-&gt;GetMetadataQueryReader(&amp;pQueryReader); } if (SUCCEEDED(hr)) { PROPVARIANT value; hr = pQueryReader-&gt;GetMetadataByName(L"/ifd/exif/{ushort=1111}", &amp;value); } </code></pre> <p>This returns E_INVALIDARG error.</p> <p>I'd appreciate some help in understanding how this works. I feel like I have not understood the documentation correctly.</p> <p>Thank you.</p>
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    1. USSau
    1. USSau
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      1. POHow do I use the WIC API to read/write custom EXIF data?
      1. USRoman R.
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      1. POHow do I use the WIC API to read/write custom EXIF data?
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    1. CODoes the `value` need to be initialized before using it in the call to `GetMetadataByName`? At a minimum, I would try setting `value.vt` to `VT_EMPTY`. The function says its an in/out parameter, not just an out one, so you probably should make sure it's initialized.
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      1. POHow do I use the WIC API to read/write custom EXIF data?
      1. USAdrian McCarthy
 

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