wp-includes/media.php:204Scales an image to fit a particular size (such as 'thumb' or 'medium').
$idint$sizestring|int[]optional'medium'array|false$0string
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One hook fires while image_downsize() runs, in this order:
Filters whether to preempt the output of image_downsize().
function image_downsize( $id, $size = 'medium' ) { $is_image = wp_attachment_is_image( $id ); /** * Filters whether to preempt the output of image_downsize(). * * Returning a truthy value from the filter will effectively short-circuit * down-sizing the image, returning that value instead. * * @since 2.5.0 * * @param bool|array $downsize Whether to short-circuit the image downsize. * @param int $id Attachment ID for image. * @param string|int[] $size Requested image size. Can be any registered image size name, or * an array of width and height values in pixels (in that order). */ $out = apply_filters( 'image_downsize', false, $id, $size ); if ( $out ) { return $out; } $img_url = wp_get_attachment_url( $id ); $meta = wp_get_attachment_metadata( $id ); $width = 0; $height = 0; $is_intermediate = false; $img_url_basename = wp_basename( $img_url ); /* * If the file isn't an image, attempt to replace its URL with a rendered image from its meta. * Otherwise, a non-image type could be returned. */ if ( ! $is_image ) { if ( ! empty( $meta['sizes']['full'] ) ) { $img_url = str_replace( $img_url_basename, $meta['sizes']['full']['file'], $img_url ); $img_url_basename = $meta['sizes']['full']['file']; $width = $meta['sizes']['full']['width']; $height = $meta['sizes']['full']['height']; } else { return false; } } // Try for a new style intermediate size. $intermediate = image_get_intermediate_size( $id, $size ); if ( $intermediate ) { $img_url = str_replace( $img_url_basename, $intermediate['file'], $img_url ); $width = $intermediate['width']; $height = $intermediate['height']; $is_intermediate = true; } elseif ( 'thumbnail' === $size && ! empty( $meta['thumb'] ) && is_string( $meta['thumb'] ) ) { // Fall back to the old thumbnail. $imagefile = get_attached_file( $id ); $thumbfile = str_replace( wp_basename( $imagefile ), wp_basename( $meta['thumb'] ), $imagefile ); if ( file_exists( $thumbfile ) ) { $info = wp_getimagesize( $thumbfile ); if ( $info ) { $img_url = str_replace( $img_url_basename, wp_basename( $thumbfile ), $img_url ); $width = $info[0]; $height = $info[1]; $is_intermediate = true; } } } if ( ! $width && ! $height && isset( $meta['width'], $meta['height'] ) ) { // Any other type: use the real image. $width = $meta['width']; $height = $meta['height']; } if ( $img_url ) { // We have the actual image size, but might need to further constrain it if content_width is narrower. list( $width, $height ) = image_constrain_size_for_editor( $width, $height, $size ); return array( $img_url, $width, $height, $is_intermediate );Introduced in 2.5.0. 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.