function initimg(parpic,maxwidth,maxheight)
{
var scale=maxwidth/maxheight;
var realscale=parpic.width/parpic.height;

if((parpic.width>=maxwidth)||(parpic.height>=maxheight))
{
if(realscale>scale)
{
parpic.width=maxwidth;
parpic.higth=  maxwidth / realscale
}
else
{
parpic.height=maxheight;
parpic.width = maxheight * realscale
}
}

}