canvas练手——ps混合图层

1. 矢量图svg不失真；位图失真
2. ps混合图层：两张图片通过正片叠底、溶解、颜色加深等合成为一张图片；
3. 目的：为了图片更少，节约内存
4. 其他方法——css3：
   mix-blend-mode: normal;          //正常
   mix-blend-mode: multiply;        //正片叠底
   mix-blend-mode: screen;          //滤色
   mix-blend-mode: overlay;         //叠加
   mix-blend-mode: darken;          //变暗
   mix-blend-mode: lighten;         //变亮
   mix-blend-mode: color-dodge;     //颜色减淡
   mix-blend-mode: color-burn;      //颜色加深
   mix-blend-mode: hard-light;      //强光
   mix-blend-mode: soft-light;      //柔光
   mix-blend-mode: difference;      //差值
   mix-blend-mode: exclusion;       //排除
   mix-blend-mode: hue;             //色相
   mix-blend-mode: saturation;      //饱和度
   mix-blend-mode: color;           //颜色
   mix-blend-mode: luminosity;      //亮度
   mix-blend-mode: initial;         //初始
   mix-blend-mode: inherit;         //继承
   mix-blend-mode: unset;           //复原
5. canvas库：https://blog.csdn.net/weixin_34395205/article/details/93886183