Javascript 使用JS计算两个矩形节点之间的直线交点偏移

我不喜欢问其他人这样的问题，但我不是一个三角专家，我需要一些帮助来计算直线相交的位置

使用Javascript和一组具有已知宽度和高度的已知矩形节点（节点的x和y位置表示每个节点的中心），我想计算线的起点和终点的线偏移，以便线只接触节点的边缘

[_____]---->[_____]

上面的ascii图显示了两个矩形节点，节点之间有一个箭头。箭头在起点或终点都不与节点相交。假设直线总是水平或垂直的，这很容易计算，但是如果直线成一定角度，那么我仍然希望直线只接触边缘

假设下面的ascii艺术有一个箭头指向目标节点（由管道符号表示）

已知变量：

• 资料来源（1）：{x，y，w，h}
• 目标（2）：{x，y，w，h}
• 线的θ（数学atan（y2-y1，x2-x1））

期望输出：

• 源节点上的交点
• 目标节点上的交点

例如：

{
    sourceIntersect: {x, y}, 
    targetIntersect: {x, y}
}

---

我发现有一个工具可以计算两条线的交点。如果我将矩形视为一组4条直线，我可以使用line intersect npm项目来获取其中一条直线的交点。在下面的SO问题中找到了解决方案

这是我的代码示例：

// first, get the sizes of the element.
// here we use getBoundingClientRect for an SVG
const clientRect = svgRectElement.getBoundingClientRect();

// extract the width and height
const w = clientRect.width;
const h = clientRect.height;

// trg represents the target point from the element above
// the x and y for trg relate to the center of the element
const top = trg.y - h / 2;
const bottom = trg.y + h / 2;
const left = trg.x - w / 2;
const right = trg.x + w / 2;

// a line extends from src{x,y} to trg{x,y} at the center of both rectangles

// another line extends from left to right at the top of the rectangle   
const topIntersect = lineIntersect.checkIntersection(src.x, src.y, trg.x, trg.y, left, top, right, top);

// another line extends from top to bottom at the right of the rectangle
const rightIntersect = lineIntersect.checkIntersection(src.x, src.y, trg.x, trg.y, right, top, right, bottom);

// another line extends from left to right at the bottom of the rectangle
const bottomIntersect = lineIntersect.checkIntersection(src.x, src.y, trg.x, trg.y, left, bottom, right, bottom);

// another line extends from top to bottom at the left of the rectangle
const leftIntersect = lineIntersect.checkIntersection(src.x, src.y, trg.x, trg.y, left, top, left, bottom);

// only one of the intersect variables above will have a value
if (topIntersect.type !== 'none' && topIntersect.point != null) {
  // topIntersect.point is the x,y of the line intersection with the top of the rectangle
} else if (rightIntersect.type !== 'none' && rightIntersect.point != null) {
  // rightIntersect.point is the x,y of the line intersection with the right of the rectangle
} else if (bottomIntersect.type !== 'none' && bottomIntersect.point != null) {
  // bottomIntersect.point is the x,y of the line intersection with the bottom of the rectangle
} else if (leftIntersect.type !== 'none' && leftIntersect.point != null) {
  // leftIntersect.point is the x,y of the line intersection with the left of the rectangle
}

---

为了得到源节点的交点，我将把它作为

trg

参数传递给我的函数，而目标节点将表示

src

参数，本质上诱使系统认为这条线是向后画的。这将提供源节点的交点，该交点在上面的变量

trg

中表示。

您需要知道直线的位置（直线上的点）…检查如何计算直线和点之间的最小距离，有很多方法。然后，由于您知道箭头的起点和终点位置，因此可以计算（距离>公差还是距离）

// first, get the sizes of the element.
// here we use getBoundingClientRect for an SVG
const clientRect = svgRectElement.getBoundingClientRect();

// extract the width and height
const w = clientRect.width;
const h = clientRect.height;

// trg represents the target point from the element above
// the x and y for trg relate to the center of the element
const top = trg.y - h / 2;
const bottom = trg.y + h / 2;
const left = trg.x - w / 2;
const right = trg.x + w / 2;

// a line extends from src{x,y} to trg{x,y} at the center of both rectangles

// another line extends from left to right at the top of the rectangle   
const topIntersect = lineIntersect.checkIntersection(src.x, src.y, trg.x, trg.y, left, top, right, top);

// another line extends from top to bottom at the right of the rectangle
const rightIntersect = lineIntersect.checkIntersection(src.x, src.y, trg.x, trg.y, right, top, right, bottom);

// another line extends from left to right at the bottom of the rectangle
const bottomIntersect = lineIntersect.checkIntersection(src.x, src.y, trg.x, trg.y, left, bottom, right, bottom);

// another line extends from top to bottom at the left of the rectangle
const leftIntersect = lineIntersect.checkIntersection(src.x, src.y, trg.x, trg.y, left, top, left, bottom);

// only one of the intersect variables above will have a value
if (topIntersect.type !== 'none' && topIntersect.point != null) {
  // topIntersect.point is the x,y of the line intersection with the top of the rectangle
} else if (rightIntersect.type !== 'none' && rightIntersect.point != null) {
  // rightIntersect.point is the x,y of the line intersection with the right of the rectangle
} else if (bottomIntersect.type !== 'none' && bottomIntersect.point != null) {
  // bottomIntersect.point is the x,y of the line intersection with the bottom of the rectangle
} else if (leftIntersect.type !== 'none' && leftIntersect.point != null) {
  // leftIntersect.point is the x,y of the line intersection with the left of the rectangle
}