Avoid calling wp_get_attachment_image_src() in srcset functions.

Improve the performance of `tevkori_get_srcset_array()` by removing the call to
`wp_get_attachment_image_src()` and use `image_get_intermediate_size()` in combination
with data we already get in the attachment post_meta to produce a srcset value. This
also gets around edge cases where the height and width attributes were being filtered
in `image_downsize()`. Updates tests.

tests/test-suite.php

@@ -198,6 +198,25 @@ function test_tevkori_get_srcset_array() {
 		$this->assertSame( $expected, $sizes );
 	}
 
+	function test_tevkori_get_srcset_array_random_size_name() {
+		// make an image
+		$id = $this->_test_img();
+		$sizes = tevkori_get_srcset_array( $id, 'foo' );
+
+		$year_month = date('Y/m');
+		$image = wp_get_attachment_metadata( $id );
+
+		$expected = array(
+			$image['sizes']['medium']['width'] => 'http://example.org/wp-content/uploads/' . $year_month = date('Y/m') . '/'
+				. $image['sizes']['medium']['file'] . ' ' . $image['sizes']['medium']['width'] . 'w',
+			$image['sizes']['large']['width'] => 'http://example.org/wp-content/uploads/' . $year_month = date('Y/m') . '/'
+				. $image['sizes']['large']['file'] . ' ' . $image['sizes']['large']['width'] . 'w',
+			$image['width'] => 'http://example.org/wp-content/uploads/' . $image['file'] . ' ' . $image['width'] .'w'
+		);
+
+		$this->assertSame( $expected, $sizes );
+	}
+
 	function test_tevkori_get_srcset_array_no_date_upoads() {
 		// Save the current setting for uploads folders
 		$uploads_use_yearmonth_folders = get_option( 'uploads_use_yearmonth_folders' );
@@ -280,7 +299,7 @@ function test_tevkori_get_srcset_array_false() {
 
 	function test_tevkori_get_srcset_array_no_width() {
 		// Filter image_downsize() output.
-		add_filter( 'image_downsize', array( $this, '_test_tevkori_get_srcset_array_no_width_filter' ) );
+		add_filter( 'wp_generate_attachment_metadata', array( $this, '_test_tevkori_get_srcset_array_no_width_filter' ) );
 
 		// Make our attachement.
 		$id = $this->_test_img();
@@ -290,14 +309,16 @@ function test_tevkori_get_srcset_array_no_width() {
 		$this->assertFalse( $srcset );
 
 		// Remove filter.
-		remove_filter( 'image_downsize', array( $this, '_test_tevkori_get_srcset_array_no_width_filter' ) );
+		remove_filter( 'wp_generate_attachment_metadata', array( $this, '_test_tevkori_get_srcset_array_no_width_filter' ) );
 	}
 
 	/**
 	 * Helper funtion to filter image_downsize and return zero values for width and height.
 	 */
-	public function _test_tevkori_get_srcset_array_no_width_filter() {
-		return array( 'http://example.org/foo.jpg', 0, 0, false );
+	public function _test_tevkori_get_srcset_array_no_width_filter( $meta ) {
+		$meta['sizes']['medium']['width'] = 0;
+		$meta['sizes']['medium']['height'] = 0;
+		return $meta;
 	}
 
 	function test_tevkori_get_srcset_string() {

wp-tevko-responsive-images.php

@@ -179,41 +179,45 @@ function tevkori_get_sizes_string( $id, $size = 'thumbnail', $args = null ) {
 function tevkori_get_srcset_array( $id, $size = 'thumbnail' ) {
 	$arr = array();
 
-	// See which image is being returned and bail if none is found.
-	if ( ! $img = wp_get_attachment_image_src( $id, $size ) ) {
-		return false;
-	}
+	// Get the intermediate size.
+	$image = image_get_intermediate_size( $id, $size );
+	// Get the post meta.
+	$img_meta = wp_get_attachment_metadata( $id );
 
-	// Break image data into url, width, and height.
-	list( $img_url, $img_width, $img_height ) = $img;
+	// Extract the height and width from the intermediate or the full size.
+	$img_width = ( $image ) ? $image['width'] : $img_meta['width'];
+	$img_height = ( $image ) ? $image['height'] : $img_meta['height'];
 
-	// If we have no width to work with, we should bail (see issue #118).
-	if ( 0 == $img_width ) {
+	// Bail early if the width isn't greater that zero.
+	if ( ! $img_width > 0 ) {
 		return false;
 	}
 
-	// Get the image meta data and bail if none is found.
-	if ( ! is_array( $img_meta = wp_get_attachment_metadata( $id ) ) ) {
-		return false;
+	// Use the url from the intermediate size or build the url from the metadata.
+	if ( ! empty( $image['url'] ) ) {
+		$img_url = $image['url'];
+	} else {
+		$uploads_dir = wp_upload_dir();
+		$img_file = ( $image ) ? path_join( dirname( $img_meta['file'] ) , $image['file'] ) : $img_meta['file'];
+		$img_url = $uploads_dir['baseurl'] . '/' . $img_file;
 	}
 
-	// Build an array with image sizes.
 	$img_sizes = $img_meta['sizes'];
 
 	// Add full size to the img_sizes array.
 	$img_sizes['full'] = array(
 		'width'  => $img_meta['width'],
 		'height' => $img_meta['height'],
-		'file'   => basename( $img_meta['file'] )
+		'file'   => wp_basename( $img_meta['file'] )
 	);
 
 	// Calculate the image aspect ratio.
 	$img_ratio = $img_height / $img_width;
 
 	/*
 	 * Images that have been edited in WordPress after being uploaded will
-	 * contain a unique hash. We look for that hash and use it later to filter
-	 * out images that are leftovers from previous renditions.
+	 * contain a unique hash. Look for that hash and use it later to filter
+	 * out images that are leftovers from previous versions.
 	 */
 	$img_edited = preg_match( '/-e[0-9]{13}/', $img_url, $img_edit_hash );