If the ratio of width and height between image and object are the same, then the image is not distored.
However, in real case, the ratio of width and height  between image and object are not the same.

width[sub]image[/sub]/width[sub]object[/sub] ? height[sub]image[/sub] /height[sub]object[/sub]

That is the reason I said the image is a distoration of the object.
Because the relation betweeb object and image are calculated from:
1/p +1/q =1/f
and
height[sub]image[/sub] /height[sub]object[/sub]= q/p

for object with width w, at position p
1/(p-w/2)+1/q1=1/f
1/(p+w/2)+1/q2=1/f
The width of the image is |q2-q1| !
The height of the image are between q2/(p+w/2) and q1/([-w/2)

Forexample:
The object is the small rectangle at the left side of the following image.
However, the image is not a square any more. And
[img]http://www.phy.ntnu.edu.tw/java/thinLens/telescope.gif[/img]