一个很简单的颜色混合函数 只要提供前景色和背景色以及 Alpha 就可返回混合后的颜色 不太适合大型图像的混合 比较适合小图标 (附带示例)-a very simple color mixing function for as long as the foreground color and background color and can be returned to the Alpha mixed after less suitable for the large-scale c