Code:

procedure TForm1.Button1Click(Sender: TObject);

var

b : tbitmap;

fr: TFormatRange;

r : TRect;

begin

b:=tbitmap.create;

b.width:=rxrichedit1.width;

b.height:=rxrichedit1.height;

r:=rect(0,0,RXRichEdit1.Width*screen.Pixelsperinch,

   RXRichEdit1.Height*screen.Pixelsperinch);

fr.hdc:=b.Canvas.handle;

fr.hdctarget:=b.Canvas.handle;

fr.rc:=r;

fr.rcpage:=r;

fr.chrg.cpMin:=0;

fr.chrg.cpMax:=-1;

Sendmessage(RXRichEdit1.handle,EM_FORMATRANGE,1,longint(@fr));

image1.Picture.assign(b);

b.free;

end;