Source

File: wp-admin/includes/image.php

function wp_read_image_metadata( $file ) {
	if ( ! file_exists( $file ) ) {
		return false;
	}

	list( , , $image_type ) = @getimagesize( $file );

	/*
	 * EXIF contains a bunch of data we'll probably never need formatted in ways
	 * that are difficult to use. We'll normalize it and just extract the fields
	 * that are likely to be useful. Fractions and numbers are converted to
	 * floats, dates to unix timestamps, and everything else to strings.
	 */
	$meta = array(
		'aperture'          => 0,
		'credit'            => '',
		'camera'            => '',
		'caption'           => '',
		'created_timestamp' => 0,
		'copyright'         => '',
		'focal_length'      => 0,
		'iso'               => 0,
		'shutter_speed'     => 0,
		'title'             => '',
		'orientation'       => 0,
		'keywords'          => array(),
	);

	$iptc = array();
	/*
	 * Read IPTC first, since it might contain data not available in exif such
	 * as caption, description etc.
	 */
	if ( is_callable( 'iptcparse' ) ) {
		@getimagesize( $file, $info );

		if ( ! empty( $info['APP13'] ) ) {
			$iptc = @iptcparse( $info['APP13'] );

			// Headline, "A brief synopsis of the caption".
			if ( ! empty( $iptc['2#105'][0] ) ) {
				$meta['title'] = trim( $iptc['2#105'][0] );
				/*
				* Title, "Many use the Title field to store the filename of the image,
				* though the field may be used in many ways".
				*/
			} elseif ( ! empty( $iptc['2#005'][0] ) ) {
				$meta['title'] = trim( $iptc['2#005'][0] );
			}

			if ( ! empty( $iptc['2#120'][0] ) ) { // Description / legacy caption.
				$caption = trim( $iptc['2#120'][0] );

				mbstring_binary_safe_encoding();
				$caption_length = strlen( $caption );
				reset_mbstring_encoding();

				if ( empty( $meta['title'] ) && $caption_length < 80 ) {
					// Assume the title is stored in 2:120 if it's short.
					$meta['title'] = $caption;
				}

				$meta['caption'] = $caption;
			}

			if ( ! empty( $iptc['2#110'][0] ) ) { // Credit.
				$meta['credit'] = trim( $iptc['2#110'][0] );
			} elseif ( ! empty( $iptc['2#080'][0] ) ) { // Creator / legacy byline.
				$meta['credit'] = trim( $iptc['2#080'][0] );
			}

			if ( ! empty( $iptc['2#055'][0] ) && ! empty( $iptc['2#060'][0] ) ) { // Created date and time.
				$meta['created_timestamp'] = strtotime( $iptc['2#055'][0] . ' ' . $iptc['2#060'][0] );
			}

			if ( ! empty( $iptc['2#116'][0] ) ) { // Copyright.
				$meta['copyright'] = trim( $iptc['2#116'][0] );
			}

			if ( ! empty( $iptc['2#025'][0] ) ) { // Keywords array.
				$meta['keywords'] = array_values( $iptc['2#025'] );
			}
		}
	}

	$exif = array();

	/**
	 * Filters the image types to check for exif data.
	 *
	 * @since 2.5.0
	 *
	 * @param array $image_types Image types to check for exif data.
	 */
	$exif_image_types = apply_filters( 'wp_read_image_metadata_types', array( IMAGETYPE_JPEG, IMAGETYPE_TIFF_II, IMAGETYPE_TIFF_MM ) );

	if ( is_callable( 'exif_read_data' ) && in_array( $image_type, $exif_image_types, true ) ) {
		$exif = @exif_read_data( $file );

		if ( ! empty( $exif['ImageDescription'] ) ) {
			mbstring_binary_safe_encoding();
			$description_length = strlen( $exif['ImageDescription'] );
			reset_mbstring_encoding();

			if ( empty( $meta['title'] ) && $description_length < 80 ) {
				// Assume the title is stored in ImageDescription.
				$meta['title'] = trim( $exif['ImageDescription'] );
			}

			if ( empty( $meta['caption'] ) && ! empty( $exif['COMPUTED']['UserComment'] ) ) {
				$meta['caption'] = trim( $exif['COMPUTED']['UserComment'] );
			}

			if ( empty( $meta['caption'] ) ) {
				$meta['caption'] = trim( $exif['ImageDescription'] );
			}
		} elseif ( empty( $meta['caption'] ) && ! empty( $exif['Comments'] ) ) {
			$meta['caption'] = trim( $exif['Comments'] );
		}

		if ( empty( $meta['credit'] ) ) {
			if ( ! empty( $exif['Artist'] ) ) {
				$meta['credit'] = trim( $exif['Artist'] );
			} elseif ( ! empty( $exif['Author'] ) ) {
				$meta['credit'] = trim( $exif['Author'] );
			}
		}

		if ( empty( $meta['copyright'] ) && ! empty( $exif['Copyright'] ) ) {
			$meta['copyright'] = trim( $exif['Copyright'] );
		}
		if ( ! empty( $exif['FNumber'] ) ) {
			$meta['aperture'] = round( wp_exif_frac2dec( $exif['FNumber'] ), 2 );
		}
		if ( ! empty( $exif['Model'] ) ) {
			$meta['camera'] = trim( $exif['Model'] );
		}
		if ( empty( $meta['created_timestamp'] ) && ! empty( $exif['DateTimeDigitized'] ) ) {
			$meta['created_timestamp'] = wp_exif_date2ts( $exif['DateTimeDigitized'] );
		}
		if ( ! empty( $exif['FocalLength'] ) ) {
			$meta['focal_length'] = (string) wp_exif_frac2dec( $exif['FocalLength'] );
		}
		if ( ! empty( $exif['ISOSpeedRatings'] ) ) {
			$meta['iso'] = is_array( $exif['ISOSpeedRatings'] ) ? reset( $exif['ISOSpeedRatings'] ) : $exif['ISOSpeedRatings'];
			$meta['iso'] = trim( $meta['iso'] );
		}
		if ( ! empty( $exif['ExposureTime'] ) ) {
			$meta['shutter_speed'] = (string) wp_exif_frac2dec( $exif['ExposureTime'] );
		}
		if ( ! empty( $exif['Orientation'] ) ) {
			$meta['orientation'] = $exif['Orientation'];
		}
	}

	foreach ( array( 'title', 'caption', 'credit', 'copyright', 'camera', 'iso' ) as $key ) {
		if ( $meta[ $key ] && ! seems_utf8( $meta[ $key ] ) ) {
			$meta[ $key ] = utf8_encode( $meta[ $key ] );
		}
	}

	foreach ( $meta['keywords'] as $key => $keyword ) {
		if ( ! seems_utf8( $keyword ) ) {
			$meta['keywords'][ $key ] = utf8_encode( $keyword );
		}
	}

	$meta = wp_kses_post_deep( $meta );

	/**
	 * Filters the array of meta data read from an image's exif data.
	 *
	 * @since 2.5.0
	 * @since 4.4.0 The `$iptc` parameter was added.
	 * @since 5.0.0 The `$exif` parameter was added.
	 *
	 * @param array  $meta       Image meta data.
	 * @param string $file       Path to image file.
	 * @param int    $image_type Type of image, one of the `IMAGETYPE_XXX` constants.
	 * @param array  $iptc       IPTC data.
	 * @param array  $exif       EXIF data.
	 */
	return apply_filters( 'wp_read_image_metadata', $meta, $file, $image_type, $iptc, $exif );

}