uses 
 JPEG; 

procedure JPEGtoBMP(const FileName: TFileName); 
var 
 jpeg: TJPEGImage; 
 bmp: TBitmap; 
begin 
 jpeg := TJPEGImage.Create; 
 try 
 jpeg.CompressionQuality := 100; {Default Value} 
 jpeg.LoadFromFile(FileName); 
 bmp := TBitmap.Create; 
 try 
 bmp.Assign(jpeg); 
 bmp.SaveTofile(ChangeFileExt(FileName, '.bmp')); 
 finally 
 bmp.Free 
 end; 
 finally 
 jpeg.Free 
 end; 
end; 


{ 
 CompressionQuality (default 100): 
 Set a value between 1..100, depending on your need of quality and 
 image file size. 1 = Smallest file size, 100 = Best quality. 
}