Constrain Width and Height of Image or run a check.

Right now if someone uploads an image that is 2048*1536 it will break the site. There is a way to set that in the image field admin so that you can set it for 640*480. I am using the new HEAD version. When I set the maximum width and height in the text box and go to upload an image for the site that is bigger then what I have set in those fields there is no check to make sure that the image is not larger then the 640*480 that I put in the Max width and height. It will allow me to upload any image of any size at the moment.