use gujarati fonts shruti with tcpdf

I want to use gujarati fonts in pdf. I used TCPDF V6.4.4. I am using google indic for input gujarati text. My php version is 8.0. I put shruti fonts into fonts folder. I wrote these code.

require_once('TCPDF/tcpdf.php');
$patient1 = "ચિરાગ";
    $patient2 = "પરમાર";
    $patient3 = "મારું";
    $patient4 = "નામ";
    $patient5 = "કલીનીક";

    $doctorname="doctorname";
    $filename="filename1.pdf";
    $billreport = "Billreport";
    $pdf_clinicname="pdf clicnicname"; $pdf_address="pdf address";

    $html = '';
    $pdfheader='';
    $html .= '<style>
              body { 
        font-size: 13px;
        color: #000;
        overflow-x: hidden;
        font: inherit;
        }
        .pdfprint{width: 100%; clear: both; float: left; margin: 10px; padding: 10px; color: #000; border: 1px solid #121010; }
        .pdfheader{}
        .leftheader{}
        .red{color: red;}
        .clinicname{font-size: 24px; font-weight: 800;}
        .doctorname{font-size: 20px; font-weight: 800;}
        .doctordegree{font-weight: 600; color: #000; font-size: 12px;}
        .dtagline{}
        .hrtag{clear:both; width: 100%; border: 1px solid #d9d6d6; height: 1px;}
        .namebox{float: left; background-color: #eee;border: 1px solid #e5e6e7;border-radius: 1px; color: inherit; display: block; padding: 6px 6px; margin-right: 10px;}
        .pipesymbol{padding-left: 15px; padding-right: 15px;}
        .rx{font-size: x-large;width: 49%; float: left;}
        .rx2{font-size: x-large; }
        .doclasssection{padding-left: 15px;}
        .patientsection{width: 100%;clear: both; float: left; padding-top: 5px; padding-bottom: 10px;}
        .prescription{width: 49%; float: left;}
        .doclasssection{width: 49%; float: left;}
        .comeafter{width: 100%; float: left; clear: both;}
        .medicinetimetable{float: left; padding-left:50px;}
        </style>';
        $html .= '<body>
                <div id="wrapper">
                    <div id="page-wrapper" class="gray-bg1 dashbard-1">
                        <div id="pdfprint" class="pdfprint chirag1">';

                        $html.='<div class="patientsection" >
                    <div class="patientname">
                        <span class="namebox">'.utf8_encode($patient1).'</span>
                        <span class="namebox">Age : '.utf8_encode($patient2).'</span> <span class="namebox">'.utf8_encode($patient2).'</span>
                        <span class="namebox">ID : '.utf8_encode($patient3).'</span>
                        <span class="namebox">Case No : '.utf8_encode($patient4).'</span>
                        <span class="namebox">Date : '.utf8_encode($patient5).'</span>
                    </div>
                </div> <div class="hrtag"></div>';
         $html.='</div> </div> 
        </div>'; // end wrapper id
        $html.='</body>';

        $pdf = new TCPDF(PDF_PAGE_ORIENTATION, PDF_UNIT, PDF_PAGE_FORMAT, true, 'UTF-8', false);

        // convert TTF font to TCPDF format and store it on the fonts folder
        $fontname = TCPDF_FONTS::addTTFfont('/TCPDF/fonts/shruti.ttf', 'TrueTypeUnicode', '', 96);

        // use the font
        $pdf->SetFont($fontname, '', 14, '', false);

         // set document information
    $pdf->SetCreator(PDF_CREATOR);
    //$pdf->SetAuthor('Nicola Asuni');
    $pdf->SetAuthor($doctorname);
    //$pdf->SetTitle('TCPDF Example 021');
    $pdf->SetTitle($filename);
    //$pdf->SetSubject('TCPDF Tutorial');
    $pdf->SetSubject($billreport);
    $pdf->SetHeaderData(PDF_HEADER_LOGO, PDF_HEADER_LOGO_WIDTH, utf8_encode($pdf_clinicname), utf8_encode($pdf_address));

 // set margins
    $pdf->SetMargins(PDF_MARGIN_LEFT, PDF_MARGIN_TOP, PDF_MARGIN_RIGHT);
    $pdf->SetHeaderMargin(PDF_MARGIN_HEADER);
    $pdf->SetFooterMargin(PDF_MARGIN_FOOTER);

    // set auto page breaks
    $pdf->SetAutoPageBreak(TRUE, PDF_MARGIN_BOTTOM);

    // set image scale factor
    //$pdf->setImageScale(PDF_IMAGE_SCALE_RATIO);

    // set some language-dependent strings (optional)
    if (@file_exists(dirname(__FILE__).'/lang/eng.php')) {
        require_once(dirname(__FILE__).'/lang/eng.php');
        //$pdf->setLanguageArray($l);
    }

    // set font
    $pdf->SetFont('shruti', '', 6);

   $pdf->setFontSubsetting(true);
    // add a page
    $pdf->AddPage();

    // output the HTML content
    $pdf->writeHTML(utf8_encode($html), true, 0, true, 0);

    // reset pointer to the last page
    $pdf->lastPage();

    //Close and output PDF document
    //$pdf->Output('example_021.pdf', 'I');
    $pdf->Output($filename, 'D');

When I run this code, I got this output.
pdf output

Gujrati fonts are not displayed. Please help me to display gujrati fonts into pdf. Thank you in advance.