SwiftMailer embed doesn't have access to the picture?

Question

Yii

Controller:

$res = Yii::$app->mailer->compose('hello', [
  'img'  => '/project/favicon.ico'
])

Hello.php email template:

/* @var $this \yii\web\View view component instance */
/* @var $message \yii\mail\BaseMessage instance of newly created mail message */

<img src="<?php $message->embed($img); ?>" alt="">

Result: Unable to open file for reading [/project/favicon.ico] Checked

permissions, 777