Nolan Chou

Sometimes we forgot change our file to a available name. So the plugin can help you auto change your upload file. 
I will add a filetype option of setting in next version. 
And a rename popup before the file upload if you change setting in future, default value is post_name.

wp_upload_rename

Change upload filename to random characters / random numbers / date / other by yourself.

natekinkead

When you upload a new image in WordPress, this plugin will use the file name to automatically fill in the Title, Alt text, Caption fields, and Description so you don’t have to do it manually.

Image Automatic Alt Text and Caption

Automatically fills in the Alt text, Caption, and Description from the image file name of new image uploads.

wp_upload_rename vs Image Automatic Alt Text and Caption