Irfanview resize image with same width and height without quality lost : Can you help me please?

I use irfanview batch for resize my image and i have one problem.

My problem is i want to resize all image with 1840 width and height, without no ratio and no quality lost after process.

I explain me, example if i have one image with 1700 * 1700 resize to 1840* 1840 no problem quality is ok beacause quality after resize is lowest.

But the problem with this case:if i have one image with 1920*1200 1200 is height. here if i execute this command

    "C:\irfanview\i_view32.exe" "C:\photo\C0692B\*.jpg" /resize=(1840, 1840) /resample /convert="C:\photo\C0692B\test\*.jpg"

I lost quality for height i dont want resize height beacause is lowest than resize size.

Before commande
[http://www.hostingpics.net/viewer.php?id=714806photo2.jpg][1]
After:
[http://www.hostingpics.net/viewer.php?id=445086photo2.jpg][1]

For this example, i want to center image and add blanck for obtain image 1840 *1840 withotu quality lost.

It's possible?

Thanks. 


  