好的，所以我似乎有工作代码，但我确信我可以做很多改进仍然是为了使它更有效等等 . 我现在也必须处理其他7个调整大小的句柄(这只是顶部 - 中间一个)：

var RADIANS = Math.PI/180;

var rotated_coords = {x: coords.x, y: coords.y};

if (shape.rotate) {

var rads = -shape.rotate*RADIANS;

var middle = {x: shape.x + shape.w/2, y: shape.y + shape.h/2}; //

middle of rotation

var offset = {

x: middle.x - coords.x,

y: middle.y - coords.y

};

rotated_coords.x = middle.x - (offset.x * Math.cos(rads) - offset.y

* Math.sin(rads));

rotated_coords.y = middle.y - (offset.x * Math.sin(rads) + offset.y

* Math.cos(rads));

}

// 1. get centre before resize

var middle = {

x: shape.x + shape.w/2,

y: shape.y + shape.h/2

};

// 2. get bottom-middle of rotated shape

var bottom_middle = {

x: middle.x - shape.h/2 * sin_th,

y: middle.y + shape.h/2 * cos_th

};

// 3. resize (get difference in height, dh) from bottom-middle point

var dh = shape.y - rotated_coords.y;

// 4. get new centre point

var new_middle = {

x: bottom_middle.x + (shape.h + dh) / 2 * sin_th,

y: bottom_middle.y - (shape.h + dh) / 2 * cos_th

};

// 5. return to non-rotated top-left point

shape.x = new_middle.x - shape.w / 2;

shape.y = new_middle.y - (shape.h + dh) / 2;

// 6. set our new height

shape.h += dh;