well you must debug it then.
Try to qDebug inside princi what you read and compare that to what u read for
system ("./princi 0 5 10 0 7 8 prueba_princi.bmp 0 0 +")
Sadly We cannot guess why you crash from the code shown.
Also you dump the arguments to qDebug before u
call start, just to see what u are sending also.
and then take it from there.