(3.0.2 - 3.0.18 only, PHP 4 >= 4.0.0)

ImageColorResolve --  Get the index of the specified color or its closest possible alternative


int imagecolorresolve (int im, int red, int green, int blue)

This function is guaranteed to return a color index for a requested color, either the exact color or the closest possible alternative.

See also imagecolorclosest().