The method of correcting digital verification code in DEDECMS _php skill

Input letter verification Code, I feel very annoying, especially to enter capital letters. It then finds the file and modifies it to a digital captcha.
Modify the location of the file verification code file
include\validateimg.php
Found it
For ($i =0 $i <4; $i + +)
{
$rndstring. = Chr (Mt_rand (65,90));
}
Change into
For ($i =0 $i <4; $i + +)
{
$rndstring. = Chr (Mt_rand (48,57));
}
This function is to produce random characters, see inside the number does not, it is to produce a character keyboard code range, the original is
Mt_rand (65,90), this 65 to 90 is the uppercase A to Z keyboard code.
Now modify to (48,57) the keyboard code that represents 0 through 9: Mt_rand (48,57).
According to this theory, it is estimated that Chinese can be produced.
and this file.
$bgcolor = Imagecolorallocate ($im, 248,212,20);
$black = Imagecolorallocate ($im, 0,0,0);
is to set the background color and text color of the generated picture. The three digits represent the red, green, and blue values of the colors. Range is 0 to 255,
Like what
0,0,0 represents Black,
255,0,0 said pure red,
The 0,255,0 represents pure green,
0,0,255 says Blue.
255.255.255 represents White.