An example WP plugin which adds functionalities to the WordPress Media Library

media-hacks.php

<?php
/**
 * @package Media_hacks
 * @version 1.0
 */
/*
Plugin Name: Media hacks
Plugin URI: http://wordpress.org/extend/plugins/#
Description: This is an example plugin 
Author: Carlo Daniele
Version: 1.0
Author URI: http://carlodaniele.it/en/
*/

/**
 * Filters the attachment fields to edit.
 *
 * @param array   $form_fields An array of attachment form fields.
 * @param WP_Post $post        The WP_Post attachment object.
 */
function media_hacks_attachment_fields_to_edit( $form_fields, $post ){
  
    // https://codex.wordpress.org/Function_Reference/wp_get_attachment_metadata

    $media_author = get_post_meta( $post->ID, 'media_author', true );
    
    $form_fields['media_author'] = array(
            'value' => $media_author ? $media_author : '',
            'label' => __( 'Author' )
        ); 


    // get post mime type
    $type = get_post_mime_type( $post->ID );

    // get the attachment path
    $attachment_path = get_attached_file( $post->ID );

    // get image metadata
    $metadata = wp_read_image_metadata( $attachment_path );

    if( 'image/jpeg' == $type ){

        if( $metadata ) {

            $exif_data = array( 
                'aperture'          => 'Aperture', 
                'camera'            => 'Camera', 
                'created_timestamp' => 'Timestamp',
                'focal_length'      => 'Focal Lenght', 
                'iso'               => 'ISO', 
                'shutter_speed'     => 'Exposure Time', 
                'orientation'       => 'Orientation' );

            foreach ( $exif_data as $key => $value ) {

                $exif = $metadata[$key];
                $form_fields[$key] = array(
                    'value' => $exif ? $exif : '',
                    'label' => __( $value ),
                    'input' => 'html',
                    'html'  => "<input type='text' class='text' readonly='readonly' name='attachments[$post->ID][$exif]' value='" . $exif . "' /><br />" 
                );
            }
        }
    }
    return $form_fields;
}
add_filter( 'attachment_fields_to_edit', 'media_hacks_attachment_fields_to_edit', 10, 2 );

/**
 * Update attachment metadata 
 *
 * @param int $post_ID Attachment ID.
 */
function media_hacks_edit_attachment( $attachment_id ){

    if ( isset( $_REQUEST['attachments'][$attachment_id]['media_author'] ) ) {
    
        $media_author = $_REQUEST['attachments'][$attachment_id]['media_author'];
    
        update_post_meta( $attachment_id, 'media_author', $media_author );
    
    }

}
add_action( 'edit_attachment', 'media_hacks_edit_attachment' );

/**
 * Filters the post content.
 *
 * @param string $content Content of the current post.
 */
function media_hacks_the_content( $content ){
    global $post;

    if( is_attachment() && 'image/jpeg' == get_post_mime_type( $post->ID ) ) {
        
        $fields = wp_get_attachment_metadata( $post->ID );
        $meta = $fields['image_meta'];

        if( ! empty( $meta['camera'] ) ){
            $custom_content = "
            <ul>
                <li>Camera: {$meta['camera']}</li>
                <li>Created timestamp: {$meta['created_timestamp']}</li>
                <li>Aperture: {$meta['aperture']}</li>
                <li>Focal length: {$meta['focal_length']}</li>
                <li>ISO: {$meta['iso']}</li>
                <li>Shutter speed: {$meta['shutter_speed']}</li>
                <li>Orientation: {$meta['orientation']}</li>
            </ul>";
            $content .= $custom_content; 
        }  
    }   

    return $content;
}
add_filter( 'the_content', 'media_hacks_the_content' );

/**
 * Registers post type arguments.
 *
 * @param array   $args       Array of arguments for a post type
 * @param string  $post_type  Post type key
 */
function media_hacks_register_post_type_args( $args, $post_type ){
    if( $post_type == 'attachment' ){
        $args['has_archive'] = true;
    }
    return $args;
}
add_filter( 'register_post_type_args', 'media_hacks_register_post_type_args', 10, 2 );

/**
 * Set custom query vars for WP_Query
 *
 * @param WP_Query &$this The WP_Query instance (passed by reference).
 */
function media_hacks_pre_get_posts( $query ){
    if ( !is_admin() && $query->is_main_query() ) {

        if( is_post_type_archive('attachment') ){
            $query->set('post_mime_type', 'image/jpeg');
            $query->set( 'post_status', 'inherit' );
        }
    }
}
add_action( 'pre_get_posts', 'media_hacks_pre_get_posts' );