

<dl>
<dt><b>-sigma=</b><i>number</i>

<dd>This is the sigma parameter of the Gaussian function (if it were a 
Gaussian probability function, this would be its the standard deviation).
The higher the number, the more spread out the function is.  Normally, you
want to make this number low enough that the function reaches zero value
before the edge of your image.

<p><i>number</i> is in units of pixels.

<p>This option is required.  There is no default.

<dt><b>-maxval=</b><i>number</i>
<dd>This is the maxva