/* syntax:
The amount of the conversion, specified as a <number> or a <percentage>.
A value under 100% desaturates the image, while a value over 100% 
super-saturates it. A value of 0% is completely unsaturated, while
a value of 100% leaves the input unchanged. The lacuna value for 
interpolation is 1. */
saturate(amount)

/* examples */
filter: saturate(1);
filter: saturate(2);
filter: saturate(50%);