如何在ASP.NET应用程序中使用图像大小调整来防止DOS攻击？

I'm currently developing a site where users can upload images to use as avatars, I know this makes me sound a little paranoid but I was wondering what if a malicious user uploads an image with incredibly large dimensions that will eat the server memory (as a DOS attack), I already have a limit on the file size that can be uploaded (250 k) but even that size can allow for an image with incredibly large dimensions if the image for example is a JPEG that contains one color and created with a very low quality setting. Taking into consideration that the image is uploaded as a bitmap in memory when being resized (ie. not compressed), I wonder if such DOS attacks occur, even to check the image dimensions it has to be uploaded in memory first, did you hear about any attacks that exploited this? Am I too worried?I'm currently developing a site where users can