WordPress/wp-content/themes/twentytwelve/image.php

<?php
/**
 * The template for displaying image attachments
 *
 * @link https://developer.wordpress.org/themes/basics/template-hierarchy/
 *
 * @package WordPress
 * @subpackage Twenty_Twelve
 * @since Twenty Twelve 1.0
 */

get_header(); ?>

	<div id="primary" class="site-content">
		<div id="content" role="main">

		<?php
		while ( have_posts() ) :
			the_post();
			?>

				<article id="post-<?php the_ID(); ?>" <?php post_class( 'image-attachment' ); ?>>
					<header class="entry-header">
						<h1 class="entry-title"><?php the_title(); ?></h1>

						<footer class="entry-meta">
							<?php
								$metadata = wp_get_attachment_metadata();
								printf(
									/* translators: 1: date, 2: date, 3: attachment URL, 4: image width in pixels, 5: image height in pixels, 6: post parent permalink, 7: post parent title, 8: post parent title */
									__( '<span class="meta-prep meta-prep-entry-date">Published </span> <span class="entry-date"><time class="entry-date" datetime="%1$s">%2$s</time></span> at <a href="%3$s" title="Link to full-size image">%4$s &times; %5$s</a> in <a href="%6$s" title="Return to %7$s" rel="gallery">%8$s</a>.', 'twentytwelve' ),
									esc_attr( get_the_date( 'c' ) ),
									esc_html( get_the_date() ),
									esc_url( wp_get_attachment_url() ),
									$metadata['width'],
									$metadata['height'],
									esc_url( get_permalink( $post->post_parent ) ),
									esc_attr( strip_tags( get_the_title( $post->post_parent ) ) ),
									get_the_title( $post->post_parent )
								);
							?>
							<?php edit_post_link( __( 'Edit', 'twentytwelve' ), '<span class="edit-link">', '</span>' ); ?>
						</footer><!-- .entry-meta -->

						<nav id="image-navigation" class="navigation" role="navigation">
							<span class="previous-image"><?php previous_image_link( false, __( '&larr; Previous', 'twentytwelve' ) ); ?></span>
							<span class="next-image"><?php next_image_link( false, __( 'Next &rarr;', 'twentytwelve' ) ); ?></span>
						</nav><!-- #image-navigation -->
					</header><!-- .entry-header -->

					<div class="entry-content">

						<div class="entry-attachment">
							<div class="attachment">
			<?php
			/*
			* Grab the IDs of all the image attachments in a gallery so we can get the URL of the next adjacent image in a gallery,
			* or the first image (if we're looking at the last image in a gallery), or, in a gallery of one, just the link to that image file
			*/
			$attachments = array_values(
				get_children(
					array(
						'post_parent'    => $post->post_parent,
						'post_status'    => 'inherit',
						'post_type'      => 'attachment',
						'post_mime_type' => 'image',
						'order'          => 'ASC',
						'orderby'        => 'menu_order ID',
					)
				)
			);
			foreach ( $attachments as $k => $attachment ) :
				if ( $attachment->ID == $post->ID ) {
					break;
				}
endforeach;

			// If there is more than 1 attachment in a gallery
			if ( count( $attachments ) > 1 ) :
				$k++;
				if ( isset( $attachments[ $k ] ) ) :
					// get the URL of the next image attachment
					$next_attachment_url = get_attachment_link( $attachments[ $k ]->ID );
				else :
					// or get the URL of the first image attachment
					$next_attachment_url = get_attachment_link( $attachments[0]->ID );
				endif;
else :
	// or, if there's only 1 image, get the URL of the image
	$next_attachment_url = wp_get_attachment_url();
endif;
?>
								<a href="<?php echo esc_url( $next_attachment_url ); ?>" title="<?php the_title_attribute(); ?>" rel="attachment">
													<?php
													/**
													 * Filter the image attachment size to use.
													 *
													 * @since Twenty Twelve 1.0
													 *
													 * @param array $size {
													 *     @type int The attachment height in pixels.
													 *     @type int The attachment width in pixels.
													 * }
													 */
													$attachment_size = apply_filters( 'twentytwelve_attachment_size', array( 960, 960 ) );
													echo wp_get_attachment_image( $post->ID, $attachment_size );
													?>
								</a>

								<?php if ( ! empty( $post->post_excerpt ) ) : ?>
								<div class="entry-caption">
									<?php the_excerpt(); ?>
								</div>
								<?php endif; ?>
							</div><!-- .attachment -->

						</div><!-- .entry-attachment -->

						<div class="entry-description">
							<?php the_content(); ?>
							<?php
							wp_link_pages(
								array(
									'before' => '<div class="page-links">' . __( 'Pages:', 'twentytwelve' ),
									'after'  => '</div>',
								)
							);
							?>
						</div><!-- .entry-description -->

					</div><!-- .entry-content -->

				</article><!-- #post -->

				<?php comments_template(); ?>

			<?php endwhile; // end of the loop. ?>

		</div><!-- #content -->
	</div><!-- #primary -->

<?php get_footer(); ?>