TBitmap for the current page or any requested pageproperty Thumbnail: TBitmap; // read only
function ExtractThumbnail(PageNumber: Integer): TBitmap;
Thumbnail decodes the current page’s optional /Thumb image into an owned TBitmap
ExtractThumbnail performs the same operation for any valid one-based page number without changing PageNumber or invalidating current-page caches
Both APIs return nil when the page has no embedded thumbnail; the caller owns and must free a returned bitmap
RenderPageThumbnail when the page has no /Thumb entryExtractThumbnail returns nil for an inactive document or an out-of-range page number
var Preview: TBitmap;
begin
Preview := Pdf1.ExtractThumbnail(3);
try
if Preview <> nil then
Image1.Picture.Assign(Preview);
finally
Preview.Free;
end;
end;