var
  SrcBitmap: TBitmap;
  DstBitmap: TBitmap;
  JPEGImage: TJPEGImage;
begin
  SrcBitmap := TBitmap.Create;
  try
    JPEGImage := TJPEGImage.Create;
    try
      JPEGImage.LoadFromFile('C:\Image.jpg');
      SrcBitmap.Assign(JPEGImage);
    finally
      JPEGImage.Free;
    end;

    DstBitmap := TBitmap.Create;
    try
      DstBitmap.Width := 100;
      DstBitmap.Height := 100;

      SetStretchBltMode(DstBitmap.Canvas.Handle, HALFTONE);
      StretchBlt(
        DstBitmap.Canvas.Handle, 0, 0, DstBitmap.Width, DstBitmap.Height,
        SrcBitmap.Canvas.Handle, 0, 0, SrcBitmap.Width, SrcBitmap.Height,
        SRCCOPY
      );

      Image1.Picture.Assign(DstBitmap);
    finally
      DstBitmap.Free;
    end;

  finally
    SrcBitmap.Free;
  end;
end;