旋转后找到矩形的顶点 [英] Find vertices of rectangle after rotating it
问题描述
这个函数计算你需要的东西。 'pivot'是旋转的起点(在你的情况下矩形的中心)。
函数rotatePoint(pivot,point ,角度){
//顺时针旋转,以弧度表示的角度
var x = Math.round((Math.cos(angle)*(point [0] - pivot [0])) -
(Math.sin(angle)*(point [1] - pivot [1]))+
pivot [0]),
y = Math.round((Math.sin(angle)* (point [0] - pivot [0]))+
(Math.cos(angle)*(point [1] - pivot [1]))+
pivot [1]);
return [x,y];
};
将度数转换为randians:
函数degToRad(deg){
return deg * Math.PI / 180;
}
So I admit I didn't really know how to phrase the question. But a full explanation should help shed some light. Here is what I know. I have a rectanlge drawn on an HTML5 Canvas. I know the points of all 4 corners and the width and height. From this I can calculate the mid-point. What I want to know is if I rotate the rectangle n degress, what the new points will be. So for example I want to rotate it 45deg from the center point. What will the new vertices of the four corners be? Hopefully that fully explains what I'm looking for. Code examples, preferably in JavaScript, would be great. Thanks in advance.
This function calculates what you need. `pivot' is the origin of the rotation (the center of the rectangle in your case).
function rotatePoint(pivot, point, angle) {
// Rotate clockwise, angle in radians
var x = Math.round((Math.cos(angle) * (point[0] - pivot[0])) -
(Math.sin(angle) * (point[1] - pivot[1])) +
pivot[0]),
y = Math.round((Math.sin(angle) * (point[0] - pivot[0])) +
(Math.cos(angle) * (point[1] - pivot[1])) +
pivot[1]);
return [x, y];
};
To convert the degrees to randians:
function degToRad(deg) {
return deg * Math.PI / 180;
}
这篇关于旋转后找到矩形的顶点的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!