Error message: "file_get_contents(): read of 8192 bytes failed with errno=21 Is a directory"

[ntgraph]

Hi,
here is my code
$mpdf = new Mpdf();
$html = view($quoteTemplate, $payload)->render();
$lastPageFooter = view($lastPageFooterTemplate, $payload)->render();

    $mpdf->WriteHTML($html);

    $mpdf->SetHTMLFooter($lastPageFooter);

    $fileName = $quote->quote_number . '.pdf';

    return response()->json([
        'data' => [
            'pdf' => base64_encode($mpdf->output('', 'S')),
            'filename' => $fileName,
        ]
    ]);

and I get this message error, can you give me a hint to solve this problem.
file: "/vendor/mpdf/mpdf/src/Image/ImageProcessor.php"
line: 230

Below is my config/pdf.php

'utf-8', 'format' => 'Letter', 'author' => 'oneApp', 'subject' => '', 'keywords' => '', 'creator' => 'Laravel Pdf', 'display_mode' => 'fullpage', 'tempDir' => base_path('storage/app/mpdf'), 'orientation' => 'P', 'margin_left' => 0, 'margin_right' => 0, 'margin_top' => 0, 'margin_bottom' => 0, ]; Please help. Thanks in advance