The avalable captcha settings, set through the src url are:
width = (width of captcha in pixels)
height = (height of captcha in pixels)
characters = (number of characters)
bgcolor = (hex color of background, do not include #)
textcolor = (hex color of text, do not include #)
noisecolor = (hex color of random noise, do not include #)
font = (path to .tff file that defines the font to use)
transparent = (1 or 0 to identify whether the background should be transparent, bgcolor is used as transparent color in this case)
bgimage = (path to image to be repeated for background of captcha)
gridfreq = ( 0- 99 amount of grid lines where 0 = none and 99 = completely covered)
gridcolor = (hex color of grid lines, do not include #)
gridorder = ("in front of text" to move in front, otherwise will be behind)
noisefreq = ( 0- 99 amount of white noise where 0 = none and 99 = completely covered)
noiseorder = ("in front of text" to move in front, otherwise will be behind)
charheight = (hieght of text in pixels... text will still automatically be shrunk if it will not fit based on the width and number of characters so this setting can only be effectively used to shrink text and not make it larger since it will always shrink to fit)
so if you add or alter their values in the image src you should be able to get the effect you want. Looks like you would want to lower the noisefreq value to reduce white noise.
