Display math powers using Ruby PDF::Writer or Ruport?

Question

Is there an easy way to display powers in PDF generated using the Ruby PDF::Writer library? I realize that I can just print the exponent a bit higher than the base number, however I thought maybe there is some easier way to do this... such as a markup tag of some sort.

Basically, I want to cleanly display x**-2.

Thanks in advance!

score 3 · Accepted Answer · answered Feb 09 '09 at 19:00

I wrote up a quick algorithm to do what I need to do. Hopefully it will work for you as well. The only requirement is that you use PDF::Writer. The method below is using PDF::Writer and Ruport. However, if you aren't using Ruport, the only thing you need to change is the "draw_text" method. Substitute it with the PDF::Writer "text" method.

def draw_text_with_exponent(text, left, font_size)
    exponent_offset = 1
    font_size_reduction = 5

    words = text.split(" ")

    buffer = ""
    words.each() do |word|
        if (word.gsub("**", '') == word)
            buffer += word + " "
        else
            number = word.split("**")
            base = number[0]
            exponent = number[1]

            buffer += base
            draw_text(buffer, :left => left, :font_size => font_size)
            left += pdf_writer.text_line_width(buffer, font_size)

            pdf_writer.y+=exponent_offset
            draw_text(exponent, :left => left, :font_size => font_size - font_size_reduction)
            left += pdf_writer.text_line_width(exponent, font_size)
            buffer = ""
            pdf_writer.y-=exponent_offset
        end
    end

    if (buffer.length > 0)
        draw_text(buffer, :left => left, :font_size => font_size)
    end
end

Here is an example call:

draw_text_with_exponent("The numbers are x**2 and y**3 ok?", 50, 11)

Let me know if you have any trouble with this method or you find an answer to my original question.

-JP

Display math powers using Ruby PDF::Writer or Ruport?

1 Answers1