fix #1529 by rounding off the scaled dimension
fix #1529 by rounding off the scaled dimension

Markismus/koreader,koreader/koreader,mihailim/koreader,poire-z/koreader,NiLuJe/koreader,NickSavage/koreader,pazos/koreader,Frenzie/koreader,chihyang/koreader,poire-z/koreader,apletnev/koreader,frankyifei/koreader,koreader/koreader,houqp/koreader,Hzj-jie/koreader,Frenzie/koreader,mwoz123/koreader,lgeek/koreader,NiLuJe/koreader,robert00s/koreader