在将图像上传到媒体库之前截取图像

I've got a WordPress website where I need to have some posts with gifs as thumbnails. After researching this topic a bit I realized that I have to intercept the gif before it's passed into Media Gallery. I have no idea where to even begin as I haven't found any hooks to hook in.

How can I pass the gif, that's being uploaded, to a custom function? Is there a way to do it in WordPress?

put this function in ur functions.php of ur theme.

function custom_upload_filter( $file )
{
    // this line catch the name of the current upload file
    // and check the filetype
    $filetype = wp_check_filetype($file['name']);

    // then check the extension file if it isn't a gif file set the $file["error"] with an advertissement
    if( $filetype["ext"] != "gif" || $filetype["ext"] != "GIF )
        $file["error"] = "Please upload a file with a 'gif' extension !";

    return $file;
}
add_filter('wp_handle_upload_prefilter', 'custom_upload_filter' );

ps: after add this functions to ur theme, u can't upload anymore other file than 'gif' file

I hope that help u.