Uploading and displaying image

I have different images of different sizes. I am uploading these images to a fix path. Now when I am displaying the images in a Image control of size 280 * 280 then the image expanded dis-proportionally. For  example if it is a mobile image which height is more and width is less then in displaying view it will make height and width similar. Means the image got distorted.
How can I display it so that the area covered by image will reduce proportionally.
Please help.