(PHP 4 >= 4.0.6, PHP 5)
imagecolorresolvealpha -- Get the index of the specified color + alpha or its closest possible alternativeThis function is guaranteed to return a color index for a requested color, either the exact color or the closest possible alternative.
imageAn image resource, returned by one of the image creation functions, such as imagecreatetruecolor().
redValue of red component
greenValue of green component
blueValue of blue component
alphaA value between 0 and 127. 0 indicates completely opaque while 127 indicates completely transparent.