Issue #3327348 by a.dmitriiev: When using base64 encoded placeholder, use image style uri, not url

        $placeholder_image_url = $style->buildUrl($file->getFileUri());

        // Serve as a data URI?

        if ($placeholder_data_uri) {

          // Requesting the URL will cause the image to be created.

          $content = @file_get_contents($placeholder_image_url);

          // Get placeholder image uri.

          $placeholder_image_uri = $style->buildUri($file->getFileUri());

          // Check if placeholder image already exists, if not - create it.

          if (!file_exists($placeholder_image_uri)) {

            $style->createDerivative($file->getFileUri(), $placeholder_image_uri);

          }

          $content = @file_get_contents($placeholder_image_uri);

          // Get the mime-type of the styled image, falls back to original.

          $mime_type = function_exists('mime_content_type') ? @mime_content_type($style->buildUri($file->getFileUri())) : $file->getMimeType();

          $mime_type = function_exists('mime_content_type') ? @mime_content_type($placeholder_image_uri) : $file->getMimeType();

          // Build the data URI with matching mime-type.

          $placeholder_image_url = "data:${mime_type};base64," . base64_encode($content);

        }