[TYPO3] limitation for image resolution

[LinTong]

Hallo everybody

I would like to make a limitation JUST for the size of image. for example not larger than 800pix width or not bigger than 2Mb. [BE] [maxFileSize] does not work because the beusers are allowed to upload bigger video files. And I tried " the global max image width" property in constant  editor. But user can still upload very large image and the system converts the large image to 800pix. It does not fulfill my requirement. Is there any possibility to set a limitation just for the filesize of image or for image resolution? Thanks very much.
 
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快来看看这些猫咪有多逗，爆笑！
http://cnweb.search.live.com/video/results.aspx?q=%E5%8F%AF%E7%88%B1%E7%8C%AB%E5%92%AA&Form=MEVHAA