Zend Barcode image isn't generate correctly in CodeIgniter

Question

I used Zend barcode library to generate barcodes for inventory items in my CodeIgniter project. And used the following code to do that.

public function gen_barcode($product_code = NULL, $bcs = 'code128', $height = 60, $text = 1)
    {
        
        $drawText = ($text != 1) ? FALSE : TRUE;
        $this->load->library('zend');
        $this->zend->load('Zend/Barcode');
        $barcodeOptions = array('text' => $product_code, 'barHeight' => $height, 'drawText' => $drawText, 'factor' => 1.0);
        if (0) {
            $rendererOptions = array('imageType' => 'jpg', 'horizontalPosition' => 'center', 'verticalPosition' => 'middle');
            $imageResource = Zend_Barcode::render($bcs, 'image', $barcodeOptions, $rendererOptions);
            return $imageResource;
            
        } else {
            $rendererOptions = array('renderer' => 'svg', 'horizontalPosition' => 'center', 'verticalPosition' => 'middle');
            $imageResource = Zend_Barcode::render($bcs, 'svg', $barcodeOptions, $rendererOptions);
            header("Content-Type: image/svg+xml");
            echo $imageResource;
        }
    }

But the barcode image doesn't generate correctly. The generated image is as follows :

Generated Image

Can anyone help ?