問題描述

我從傳單 geoJSON 地圖中選擇了兩組多邊形坐標.父子坐標是坐標是:

I'm having two sets of polygon coordinates selected from leaflet geoJSON map. The parent and child coordinates are coordinates are:

var parentCoordinates=[
    [
        32.05898221582174,
        -28.31004731142091
    ],
    [
        32.05898221582174,
        -28.308044824292978
    ],
    [
        32.06134255975485,
        -28.308044824292978
    ],
    [
        32.06134255975485,
        -28.31004731142091
    ],
    [
        32.05898221582174,
        -28.31004731142091
    ]
]
var childCoordinates=[
  [
    32.059904895722866,
    -28.30970726909422
  ],
  [
    32.059904895722866,
    -28.308743809931784
  ],
  [
    32.06089194864035,
    -28.308743809931784
  ],
  [
    32.06089194864035,
    -28.30970726909422
  ],
  [
    32.059904895722866,
    -28.30970726909422
  ]
]

child在父區域內繪制如圖:

The child is drawn inside the parent area as shown in the picture:

使用 Ray Casting 算法 來確定是否點位于多邊形內，我無法確定，因為我得到的結果是錯誤的.請讓我知道我做錯了什么或任何其他方式來確定解決方案.謝謝

Using Ray Casting algorithm to determine if the point lies inside polygon I 'm not able to determine as the result I'm getting is false. Please let me know where I'm doing wrong or any other way to determine the solution.Thanks

推薦答案

我嘗試了你的算法和另一個在這里找到的 https://rosettacode.org/wiki/Ray-casting_algorithm 并且都返回正確的值.

I tried with your algorithm and another found here https://rosettacode.org/wiki/Ray-casting_algorithm and both return the right value.

也許這個小提琴可以幫助你實現:

Maybe this fiddle can help you in the implementation :

https://jsfiddle.net/4psL2hoo/1/

您的算法

// Data
var parentCoordinates=[
    [
        32.05898221582174,
        -28.31004731142091
    ],
    [
        32.05898221582174,
        -28.308044824292978
    ],
    [
        32.06134255975485,
        -28.308044824292978
    ],
    [
        32.06134255975485,
        -28.31004731142091
    ],
    [
        32.05898221582174,
        -28.31004731142091
    ]
]
var childCoordinates=[
  [
    32.059904895722866,
    -28.30970726909422
  ],
  [
    32.059904895722866,
    -28.308743809931784
  ],
  [
    32.06089194864035,
    -28.308743809931784
  ],
  [
    32.06089194864035,
    -28.30970726909422
  ],
  [
    32.059904895722866,
    -28.30970726909422
  ]
]

// Other algo
function test(point, vs) {
    // ray-casting algorithm based on
    // http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html

    var x = point[0], y = point[1];

    var inside = false;
    for (var i = 0, j = vs.length - 1; i < vs.length; j = i++) {
        var xi = vs[i][0], yi = vs[i][1];
        var xj = vs[j][0], yj = vs[j][1];

        var intersect = ((yi > y) != (yj > y))
            && (x < (xj - xi) * (y - yi) / (yj - yi) + xi);
        if (intersect) inside = !inside;
    }

    return inside;
};

for (var i = 0; i < childCoordinates.length; i++) {
     var testPoint = childCoordinates[i];
     console.log(JSON.stringify(testPoint) + '	in parentCoordinate	' + test(testPoint, parentCoordinates));
}

Rosetta 代碼算法

//https://rosettacode.org/wiki/Ray-casting_algorithm
function contains(bounds, lat, lng) {
    //https://rosettacode.org/wiki/Ray-casting_algorithm
    var count = 0;
    for (var b = 0; b < bounds.length; b++) {
        var vertex1 = bounds[b];
        var vertex2 = bounds[(b + 1) % bounds.length];
        if (west(vertex1, vertex2, lng, lat))
            ++count;
    }
    return count % 2;

    /**
     * @return {boolean} true if (x,y) is west of the line segment connecting A and B
     */
    function west(A, B, x, y) {
        if (A.y <= B.y) {
            if (y <= A.y || y > B.y ||
                x >= A.x && x >= B.x) {
                return false;
            } else if (x < A.x && x < B.x) {
                return true;
            } else {
                return (y - A.y) / (x - A.x) > (B.y - A.y) / (B.x - A.x);
            }
        } else {
            return west(B, A, x, y);
        }
    }
}

var square = {name: 'square', bounds: [{x: 32.05898221582174, y: -28.31004731142091}, {x: 32.05898221582174, y: -28.308044824292978}, {x: 32.06134255975485, y: -28.308044824292978}, {x: 32.06134255975485, y: -28.31004731142091}]};

var shapes = [square];
var testPoints = [{lng: 32.059904895722866, lat: -28.30970726909422}, {lng: 32.059904895722866, lat: -28.308743809931784}, {lng: 32.06089194864035, lat: -28.308743809931784},
    {lng: 32.06089194864035, lat: -28.30970726909422}];

for (var s = 0; s < shapes.length; s++) {
    var shape = shapes[s];
    for (var tp = 0; tp < testPoints.length; tp++) {
        var testPoint = testPoints[tp];
        console.log(JSON.stringify(testPoint) + '	in ' + shape.name + '	' + contains(shape.bounds, testPoint.lat, testPoint.lng));
    }
}

這篇關于檢查一個多邊形點是否在傳單中的另一個內部的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！