brg_add_dropzone.php

<?php

define ( 'BP_ENABLE_ROOT_PROFILES', true );
define( 'BP_DEFAULT_COMPONENT', 'settings' );

//dropzone
define( 'DROPZONEJS_PLUGIN_URL',   get_stylesheet_directory_uri() );
define( 'DROPZONEJS_PLUGIN_VERSION', '0.0.1' );
add_action( 'init', 'dropzonejs_init' );
function dropzonejs_init() {
	add_action( 'wp_enqueue_scripts', 'dropzonejs_enqueue_scripts' );
	add_shortcode( 'dropzonejs', 'dropzonejs_shortcode' );
}
function dropzonejs_enqueue_scripts() {
	wp_enqueue_script(
		'dropzonejs',
		'https://cdnjs.cloudflare.com/ajax/libs/dropzone/4.2.0/min/dropzone.min.js',
		array(),
		DROPZONEJS_PLUGIN_VERSION
	);
	
	// Load custom dropzone javascript
	wp_enqueue_script(
		'customdropzonejs',
		DROPZONEJS_PLUGIN_URL. '/js/customize_dropzonejs.js',
		array( 'dropzonejs' ),
		DROPZONEJS_PLUGIN_VERSION
	);
	
	wp_enqueue_style(
		'dropzonecss',
		'https://cdnjs.cloudflare.com/ajax/libs/dropzone/4.2.0/min/dropzone.min.css',
		array(),
		DROPZONEJS_PLUGIN_VERSION
	);
}
// Add Shortcode
function dropzonejs_shortcode( $atts ) {
	$url         = admin_url( 'admin-ajax.php' );
	$nonce_files = wp_nonce_field( 'sis_dropzone_upload', 'dzone_nonce_field' );
	$cadastro_id = $atts['cadastro_id'];
	return <<<ENDFORM
<div id="dropzone-wordpress"><form action="$url" class="dropzone needsclick dz-clickable" id="dropzone-wordpress-form">
	$nonce_files
	<div class="dz-message needsclick">
		Clique ou arraste os arquivos aqui para salvar.<br>
  	</div>
	<input type='hidden' name='action' value='submit_dropzonejs'>
	<input type='hidden' name='cadastro_id' value='$cadastro_id'>
</form></div>
ENDFORM;
}
add_action( 'wp_ajax_nopriv_submit_dropzonejs', 'dropzonejs_upload' ); //allow on front-end
add_action( 'wp_ajax_submit_dropzonejs', 'dropzonejs_upload' );

function dropzonejs_upload() {
	if ( !empty( $_FILES ) && wp_verify_nonce( $_REQUEST['dzone_nonce_field'], 'sis_dropzone_upload' ) ) {
		$dono = $_REQUEST['dono'];
		$cadastro_id = $_REQUEST['cadastro_id'];
		require_once( ABSPATH . 'wp-admin/includes/image.php' );
		require_once( ABSPATH . 'wp-admin/includes/file.php' );
		require_once( ABSPATH . 'wp-admin/includes/media.php' );
		$attachment_id = media_handle_upload( 'file', $cadastro_id );
	
		if ( is_wp_error( $attachment_id ) ) {
			echo "Erro ao salvar a imagem";
		} else {
			echo "Imagem salva com sucesso";
			update_post_meta($attachment_id, 'dono', $dono);
		}

	}
	die();
}

customize-dropzone.js

Dropzone.options.dropzoneWordpressForm = {
	acceptedFiles: "image/*", // all image mime types
	maxFiles: 6,
	uploadMultiple: false,
	maxFilesize: 5, // 5 MB
	//addRemoveLinks: true,
	//dictRemoveFile: 'X (remove)',
	init: function() {
		this.on("sending", function(file, xhr, formData) {
			formData.append("name", "value"); // Append all the additional input data of your form here
		});
		this.on("success", function (file,response){
			alert(response);
		});
	}
};