I think that this will distort your post screens. What you really need is the picture to be sized down to 80 pixels but on the biggest dimention proportionally.
If you have an image that is 120x60, then the script should read that 120 is the biggest number and size that down, while not forcing the 60 to become 80. With this mechanism the image will be proportionally sized down according to its original dimensions.
Warm regards
Nikos
