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Can't make transparency work with white

$CodeCogs\′s Photo$

18 Oct 09, 5:19PM

Technically this is a bug, but not one that we can be fixed easily or quickly. Given its a fairly minor fault, its not one we're likely to solve for sometime I'm affraid.

The problem is with the way transparent is done. When the equation image is generated we're unable to use transparency, so transparently is added by reasigning the color white to transparent. Thats ok, so long as you use any other color than white, but when the text is also white you clearly end up with nothing.

One way to get around this is use a secret option, \fg_###### (not advertised else where) which adjusts the forground color in a different way. In \fg_######, the 6 #'s are actually pairs of numbers in hex for Red, Green and Blue respectively.

i.e.

\fg_FF0000 is Red
\fb_00FF00 is Green
\fb_0000FF is Blue

Obviously you can insert any number from 00 to FF for each color, giving you 255 possibilities. Note also this option MUST go at the front of the equation and can be used only once unlike \color{ }

Back to your problem, if we use a forground color that is slightly off white, then the transparency is correctly handled, i.e.

http://latex.codecogs.com/gif.latex?\fg_f2f2f2 x^2+2

For those wondering what on earth Percy is doing (since you don't see much in the Equation editor), then here is an html page illustrating the problem and also our crude work around:

<html>
<body style="background-color:red">
<img src="http://latex.codecogs.com/gif.latex?\color{blue}\mathbf{\frac{-b\pm\sqrt{b^2-4ac}}{2a}}" />
(blue text)
<br/>
<img src="http://latex.codecogs.com/gif.latex?\color{white}\mathbf{\frac{-b\pm\sqrt{b^2-4ac}}{2a}}" />
(white text)
<br/>
<img src="http://latex.codecogs.com/gif.latex?\fg_f2f2f2 \mathbf{\frac{-b\pm\sqrt{b^2-4ac}}{2a}}" />
(off white text)
</body>
</html>