Hi
Please have a look at this similar forum thread:-
Link:- http://help-forums.adobe.com/content/adobeforums/en/experience-manager-forum/adobe-experience-manage...
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There is a community article for restricting the upload based on size of the file - http://experience-aem.blogspot.com/2014/12/aem-6-sp1-classic-ui-restrict-large-or-small-files-upload.... You can customize it and add your logic of checking the file types. You can either just check the file extensions in the javascript or invoke a backend servlet to check the file headers for the mime types. Also, this is limited to Classic UI only.
'DAM Update Asset' workflow, there you can configure which file types should be allowed. Similarly, you can write custom workflowprocess service to check the type and size of the asset and restrict the uploads accordingly.
You could create a custom sling servlet, that will upload assets for you. There you can insert you logic to restrict anything.
Link:- https://helpx.adobe.com/experience-manager/using/uploading-files-aem1.html
Link:- http://help-forums.adobe.com/content/adobeforums/en/experience-manager-forum/adobe-experience-manage...
// AEM 6.1 : DAM - Prevent adding of some asset format
I hope this would help you.
~kautuk
Kautuk Sahni