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HPSF THUMBNAIL HOW-TO
The VT_CF Format
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.
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.
The VT_CF structure looks like this:
The Clipboard Size refers to the size (in bytes) of Clipboard Data (variable size) plus the Clipboard Format (four bytes).
Clipboard Format Tag has four possible values:
Windows Clipboard Data
Windows clipboard data has four image formats for thumbnails:
Windows Metafile Format
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.
The Clipboard Data byte array looks like this when an image is stored in Windows' Clipboard WMF format.
Device Independent Bitmap
FIXME: Describe the Device Independent Bitmap format!
Macintosh Clipboard Data
FIXME: Describe the Macintosh clipboard formats!