RGB和RGBA之間的轉換

function RGB2RGBA(rgb_color,alp){
//注：rgb_color的格式爲#FFFFFFF
var r = parseInt("0x" + rgb_color.substr(1,2));
var g = parseInt("0x" + rgb_color.substr(3,2));
var b = parseInt("0x" + rgb_color.substr(5,2));
var a = alp;//爲透明度
return "rgba(" + r + "," + g + "," + b + "," + a + ")";
}


function RGBA2RGB(rgba_color){
//注：rgba_color的格式爲rgba(0,0,0,0.1)
var BGcolur = 1;
var arr = rgba_color.split("(")[1].split(")")[0].split(",");
var a = arr[3];
var r = BGcolur * (1 - a) + arr[0] * a;
var g = BGcolur * (1 - a) + arr[1] * a;
var b = BGcolur * (1 - a) + arr[2] * a;
return "rgb(" + r + "," + g + "," + b +")";
}