java - SimpleCaptcha: how to make upper-case letters always larger than lower-case letters? -

i use java-based simplecaptcha web application. notice the case of letters generated simplecaptcha hard recognize in cases. see following 2 examples:

in above, difficult know "c" in lower-case or upper-case because has same height upper-case "n" has. example:

in example, difficult know "o" upper-case or lower-case.

i hope able make upper-case letters show larger lower-case letters. or make upper-case letters have same height, , lower-case letters have same height too. maybe way is: make simplecaptcha not change size of letters or digits.