Rotate rectangle around a point

问题

How would I get 4 points rotated a certain degrees around a pointer to form a rectangle? I can rotate a point around a point, but I can't offset it to make a rectangle that isn't distorted.

回答1:

If you can rotate a point around a point then it should be easy to rotate a rectangle - you just rotate 4 points.

Here is a js function to rotate a point around an origin:

function rotate_point(pointX, pointY, originX, originY, angle) {
    angle = angle * Math.PI / 180.0;
    return {
        x: Math.cos(angle) * (pointX-originX) - Math.sin(angle) * (pointY-originY) + originX,
        y: Math.sin(angle) * (pointX-originX) + Math.cos(angle) * (pointY-originY) + originY
    };
}

And then you can do this to each point. Here is an example: http://jsfiddle.net/dahousecat/4TtvU/

Change the angle and hit run to see the result...

来源：https://stackoverflow.com/questions/4465931/rotate-rectangle-around-a-point