attachment image height en width

[ageurtse]

I would like to know how to get an attachments height and width. how could i do this.

for displaying the image i use

PHP Code:

$output .= "<img border=0 src=attachment.php?attachmentid=".$post['attachmentid']."&thumb=1>"; 


i put this in a cel from a table. but i would scale the longest size to fit in this cell so it attachment would display normal and not stretcht out.


i think i use

PHP Code:

 if ($height < $width){$output .= "<img border=0 src=attachment.php?attachmentid=".$post['attachmentid']."&thumb=1 width=100%>";} 
else 
{$output .= "<img border=0 src=attachment.php?attachmentid=".$post['attachmentid']."&thumb=1 height=100%>";}; 


but how do i get this width and height