用js语言生成一个等值线算法
时间: 2024-05-04 18:20:50 浏览: 11
好的,以下是一个简单的 JavaScript 实现等值线算法的代码:
```javascript
function contour(data, threshold) {
var contours = [];
// 辅助函数,获取数据矩阵中一个点的值
function get(x, y) {
return data[x + y * data.width];
}
// 辅助函数,获取某个点的等值线方向
// N: 1, E: 2, S: 4, W: 8
function getDirection(x, y) {
var value = 0;
if (get(x, y) < threshold) value |= 1;
if (get(x + 1, y) < threshold) value |= 2;
if (get(x + 1, y + 1) < threshold) value |= 4;
if (get(x, y + 1) < threshold) value |= 8;
return value;
}
// 辅助函数,获取某个等值线方向的顶点坐标
function getVertex(x, y, direction) {
switch (direction) {
case 1: return [x + 0.5, y];
case 2: return [x + 1, y + 0.5];
case 4: return [x + 0.5, y + 1];
case 8: return [x, y + 0.5];
case 3: return [x + 1, y];
case 6: return [x + 1, y + 1];
case 12: return [x, y + 1];
case 9: return [x, y];
case 5: return [x + 0.5, y + 0.5];
case 10: return [x + 0.5, y + 0.5];
}
}
// 辅助函数,获取某个等值线方向的下一个等值线方向
function getNextDirection(direction) {
switch (direction) {
case 1: return 8;
case 2: return 1;
case 4: return 2;
case 8: return 4;
case 3: return 12;
case 6: return 3;
case 12: return 9;
case 9: return 6;
case 5: return 10;
case 10: return 5;
}
}
// 辅助函数,判断某个等值线方向是否已经被访问过
function isVisited(x, y, direction) {
var visited = data.visited;
var index = x + y * visited.width;
return (visited[index] & direction) !== 0;
}
// 辅助函数,将某个等值线方向标记为已访问
function setVisited(x, y, direction) {
var visited = data.visited;
var index = x + y * visited.width;
visited[index] |= direction;
}
// 辅助函数,检查某个顶点是否已经在等值线中
function isInContour(x, y) {
var i, j, k, contour;
for (i = 0; i < contours.length; i++) {
contour = contours[i];
for (j = 0; j < contour.length; j++) {
if (contour[j][0] === x && contour[j][1] === y) {
return true;
}
}
}
return false;
}
// 辅助函数,将等值线添加到结果中
function addContour(contour) {
var i, j, k, x, y, vertex, exists;
for (i = 0; i < contour.length; i++) {
vertex = contour[i];
x = vertex[0];
y = vertex[1];
exists = false;
for (j = 0; j < contours.length; j++) {
for (k = 0; k < contours[j].length; k++) {
if (contours[j][k][0] === x && contours[j][k][1] === y) {
exists = true;
break;
}
}
if (exists) break;
}
if (!exists) {
contours.push(contour);
break;
}
}
}
// 辅助函数,从某个顶点开始生成等值线
function generateContour(x, y) {
var contour = [];
var direction = getDirection(x, y);
var startDirection = direction;
var vertex = getVertex(x, y, direction);
contour.push(vertex);
setVisited(x, y, direction);
while (true) {
direction = getNextDirection(direction);
if (isVisited(x, y, direction)) {
if (direction === startDirection) {
addContour(contour);
return;
}
} else {
setVisited(x, y, direction);
vertex = getVertex(x, y, direction);
contour.push(vertex);
x = Math.floor(vertex[0]);
y = Math.floor(vertex[1]);
direction = getNextDirection(direction + 8);
if (!isVisited(x, y, direction)) {
setVisited(x, y, direction);
vertex = getVertex(x, y, direction);
contour.push(vertex);
}
}
}
}
// 开始遍历数据矩阵
var x, y, direction;
for (y = 0; y < data.height - 1; y++) {
for (x = 0; x < data.width - 1; x++) {
if (isInContour(x, y)) continue;
direction = getDirection(x, y);
if (direction === 0 || direction === 15) continue;
generateContour(x, y);
}
}
return contours;
}
```
这个算法使用了双线性插值来获取数据矩阵中某个点的值,但它的实现并未包含插值部分。在使用时,你需要将数据矩阵和阈值传入这个函数,它将返回一个等值线的数组。