function ThumbnailRawData: TBytes;
| Result | TBytes. The thumbnail stream exactly as stored, with its filters still applied. Empty when the page carries no thumbnail. |
Returns the bytes as the file holds them, so a JPEG-compressed thumbnail comes back as JPEG. That is what a caller wants when the thumbnail is to be copied into another file or handed to an image decoder untouched
For pixels rather than encoded bytes, use ThumbnailDecodedData, or ExtractThumbnail for a ready-made bitmap
An empty result means no thumbnail is stored for the current page