Zend Barcode label distance ajustment

Question

I used Zend bacode library to generate barcode images of items in my codeigniter based project. The images are generted correctly as follows :

Generated Sample

Then I want to increse the hieght of the barcode image & increase the distance between two labels.

Tried

I tried with the follwing code in the controller.

$bci_size = ($style == 10 || $style == 12 ? 50 : ($style == 20 || $style == 18 ? 45 : 18));

Result

But the barcode image generated out of the label when I increase the height greater than 45. And the distance beween two labels didn't change.

Can anyone help me ?