wp-includes/media.php:1363A helper function to calculate the image sources to include in a 'srcset' attribute.
$size_arrayint[]$0int
$1int
$image_srcstring$image_metaarray$attachment_idintoptional0string|false3 hooks fire while wp_calculate_image_srcset() runs, in this order:
Pre-filters the image meta to be able to fix inconsistencies in the stored data.
Filters the maximum image width to be included in a 'srcset' attribute.
Filters an image's 'srcset' sources.
function wp_calculate_image_srcset( $size_array, $image_src, $image_meta, $attachment_id = 0 ) { /** * Pre-filters the image meta to be able to fix inconsistencies in the stored data. * * @since 4.5.0 * * @param array $image_meta The image meta data as returned by 'wp_get_attachment_metadata()'. * @param int[] $size_array { * An array of requested width and height values. * * @type int $0 The width in pixels. * @type int $1 The height in pixels. * } * @param string $image_src The 'src' of the image. * @param int $attachment_id The image attachment ID or 0 if not supplied. */ $image_meta = apply_filters( 'wp_calculate_image_srcset_meta', $image_meta, $size_array, $image_src, $attachment_id ); if ( empty( $image_meta['sizes'] ) || ! isset( $image_meta['file'] ) || strlen( $image_meta['file'] ) < 4 ) { return false; } $image_sizes = $image_meta['sizes']; // Get the width and height of the image. $image_width = (int) $size_array[0]; $image_height = (int) $size_array[1]; // Bail early if error/no width. if ( $image_width < 1 ) { return false; } $image_basename = wp_basename( $image_meta['file'] ); /* * WordPress flattens animated GIFs into one frame when generating intermediate sizes. * To avoid hiding animation in user content, if src is a full size GIF, a srcset attribute is not generated. * If src is an intermediate size GIF, the full size is excluded from srcset to keep a flattened GIF from becoming animated. */ if ( ! isset( $image_sizes['thumbnail']['mime-type'] ) || 'image/gif' !== $image_sizes['thumbnail']['mime-type'] ) { $image_sizes[] = array( 'width' => $image_meta['width'], 'height' => $image_meta['height'], 'file' => $image_basename, ); } elseif ( str_contains( $image_src, $image_meta['file'] ) ) { return false; } // Retrieve the uploads sub-directory from the full size image. $dirname = _wp_get_attachment_relative_path( $image_meta['file'] ); if ( $dirname ) { $dirname = trailingslashit( $dirname ); } $upload_dir = wp_get_upload_dir(); $image_baseurl = trailingslashit( $upload_dir['baseurl'] ) . $dirname; /* * If currently on HTTPS, prefer HTTPS URLs when we know they're supported by the domain * (which is to say, when they share the domain name of the current request). */ if ( is_ssl() && ! str_starts_with( $image_baseurl, 'https' ) ) { /* * Since the `Host:` header might contain a port, it should * be compared against the image URL using the same port. */ $parsed = parse_url( $image_baseurl ); $domain = $parsed['host'] ?? ''; if ( isset( $parsed['port'] ) ) { $domain .= ':' . $parsed['port']; } if ( $_SERVER['HTTP_HOST'] === $domain ) { $image_baseurl = set_url_scheme( $image_baseurl, 'https' ); } }Introduced in 4.4.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/media.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.