ImageColorClosestAlpha
説明
int imagecolorclosestalpha ( resource im, int red, int green, int blue, int alpha)Returns the index of the color in the palette of the image which is "closest" to the specified RGB value and alpha level.
See also imagecolorexactalpha().
注意 この関数はPHP 4.0.6で追加され、GD 2.0.1を必要とします。