Hello, I have seen the site with the graphic and the one that shows the formula to use.
I can create a similar static page with html, css and a small javascript code. The page, would have a single text box to receive the taxable income, and accordingly, would locate the corresponding offset in the chart.
I have a little doubt concerning the graphic presentation of the page, I suppose it is a bit simpler in terms of presentation, but there is no problem in this respect in any case.
I hope you find my proposal attractive.
Have a nice day.