我可以获取当前的画布上下文的旋转角度吗？(Can I get the current angle of rotation of my canvas context?)

 我想知道是否有方法获得我的画布旋转角度。 而不是用像这样的变量来跟踪它： 
 
 var angle = 0; // keeps track of the current angle of the ctx
 ctx.rotate( Math.PI / 2 );
 angle+= Math.Pi / 2;
 ...
 ctx.rotate( Math.Pi / 7 );
 angle+= Math.Pi / 7; 

I was wondering if there is a way of getting an angle of rotation of my canvas. instead of keep tracking of it with a variable like this:
 
 var angle = 0; // keeps track of the current angle of the ctx
 ctx.rotate( Math.PI / 2 );
 angle+= Math.Pi / 2;
 ...
 ctx.rotate( Math.Pi / 7 );
 angle+= Math.Pi / 7; 

原文：https://stackoverflow.com/questions/43346222