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<h1>HPSF THUMBNAIL HOW-TO</h1>
</div>
<div class="h3">
<a name="The+VT_CF+Format"></a>
<div class="h3">
<h3>The VT_CF Format</h3>
</div>
<p>Thumbnail information is stored as a VT_CF, or Thumbnail Variant. The
Thumbnail Variant is used to store various types of information in a
clipboard. The VT_CF can store information in formats for the Macintosh or
Windows clipboard.</p>
<p>There are many types of data that can be copied to the clipboard, but the
only types of information needed for thumbnail manipulation are the image
formats.</p>
<p>The <span class="codefrag">VT_CF</span> structure looks like this:</p>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
<tr class="b">
<th colspan="1" rowspan="1">Element:</th>
<td colspan="1" rowspan="1">Clipboard Size</td>
<td colspan="1" rowspan="1">Clipboard Format Tag</td>
<td colspan="1" rowspan="1">Clipboard Data</td>
</tr>
<tr class="a">
<th colspan="1" rowspan="1">Size:</th>
<td colspan="1" rowspan="1">32 bit unsigned integer (DWord)</td>
<td colspan="1" rowspan="1">32 bit signed integer (DWord)</td>
<td colspan="1" rowspan="1">variable length (byte array)</td>
</tr>
</table>
<p>The Clipboard Size refers to the size (in bytes) of Clipboard Data
(variable size) plus the Clipboard Format (four bytes).</p>
<p>Clipboard Format Tag has four possible values:</p>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
<tr class="b">
<th colspan="1" rowspan="1">Value</th>
<th colspan="1" rowspan="1">Identifier</th>
<th colspan="1" rowspan="1">Description</th>
</tr>
<tr class="a">
<td colspan="1" rowspan="1"><span class="codefrag">-1L</span></td>
<td colspan="1" rowspan="1"><span class="codefrag">CFTAG_WINDOWS</span></td>
<td colspan="1" rowspan="1">a built-in Windows© clipboard format value</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1"><span class="codefrag">-2L</span></td>
<td colspan="1" rowspan="1"><span class="codefrag">CFTAG_MACINTOSH</span></td>
<td colspan="1" rowspan="1">a Macintosh clipboard format value</td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1"><span class="codefrag">-3L</span></td>
<td colspan="1" rowspan="1"><span class="codefrag">CFTAG_FMTID</span></td>
<td colspan="1" rowspan="1">a format identifier (FMTID) This is rarely used.</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1"><span class="codefrag">0L</span></td>
<td colspan="1" rowspan="1"><span class="codefrag">CFTAG_NODATA</span></td>
<td colspan="1" rowspan="1">No data This is rarely used.</td>
</tr>
</table>
<a name="Windows+Clipboard+Data"></a>
<div class="h3">
<h3>Windows Clipboard Data</h3>
</div>
<p>Windows clipboard data has four image formats for thumbnails:</p>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
<tr class="b">
<th colspan="1" rowspan="1">Value</th>
<th colspan="1" rowspan="1">Identifier</th>
<th colspan="1" rowspan="1">Description</th>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">3</td>
<td colspan="1" rowspan="1"><span class="codefrag">CF_METAFILEPICT</span></td>
<td colspan="1" rowspan="1">Windows metafile format - recommended</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1">8</td>
<td colspan="1" rowspan="1"><span class="codefrag">CF_DIB</span></td>
<td colspan="1" rowspan="1">Device Independent Bitmap</td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">14</td>
<td colspan="1" rowspan="1"><span class="codefrag">CF_ENHMETAFILE</span></td>
<td colspan="1" rowspan="1">Enhanced Windows metafile format</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1">2</td>
<td colspan="1" rowspan="1"><span class="codefrag">CF_BITMAP</span></td>
<td colspan="1" rowspan="1">Bitmap - Obsolete - Use <span class="codefrag">CF_DIB</span> instead</td>
</tr>
</table>
<a name="Windows+Metafile+Format"></a>
<div class="h3">
<h3>Windows Metafile Format</h3>
</div>
<p>The most common format for thumbnails on the Windows platform is the
Windows metafile format. The Clipboard places and extra header in front of
a the standard Windows Metafile Format data.</p>
<p>The Clipboard Data byte array looks like this when an image is stored in
Windows' Clipboard WMF format.</p>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
<tr class="b">
<th colspan="1" rowspan="1">Identifier</th>
<td colspan="1" rowspan="1">CF_METAFILEPICT</td>
<td colspan="1" rowspan="1">mm</td>
<td colspan="1" rowspan="1">width</td>
<td colspan="1" rowspan="1">height</td>
<td colspan="1" rowspan="1">handle</td>
<td colspan="1" rowspan="1">WMF data</td>
</tr>
<tr class="a">
<th colspan="1" rowspan="1">Size</th>
<td colspan="1" rowspan="1">32 bit unsigned int</td>
<td colspan="1" rowspan="1">16 bit unsigned(?) int</td>
<td colspan="1" rowspan="1">16 bit unsigned(?) int</td>
<td colspan="1" rowspan="1">16 bit unsigned(?) int</td>
<td colspan="1" rowspan="1">16 bit unsigned(?) int</td>
<td colspan="1" rowspan="1">byte array - variable length</td>
</tr>
<tr class="b">
<th colspan="1" rowspan="1">Description</th>
<td colspan="1" rowspan="1">Clipboard WMF</td>
<td colspan="1" rowspan="1">Mapping Mode</td>
<td colspan="1" rowspan="1">Image Width</td>
<td colspan="1" rowspan="1">Image Height</td>
<td colspan="1" rowspan="1">handle to the WMF data array in memory, or 0</td>
<td colspan="1" rowspan="1">standard WMF byte stream</td>
</tr>
</table>
<a name="Device+Independent+Bitmap"></a>
<div class="h3">
<h3>Device Independent Bitmap</h3>
</div>
<p>
<strong>FIXME:</strong> Describe the Device Independent Bitmap
format!</p>
<a name="Macintosh+Clipboard+Data"></a>
<div class="h3">
<h3>Macintosh Clipboard Data</h3>
</div>
<p>
<strong>FIXME:</strong> Describe the Macintosh clipboard formats!</p>
<div id="authors" align="right">by Drew Varner</div>
</div>
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