如何从 Javascript 中的瓦片 map 中的一点计算瓦片

Question

I have a Tilemap written in plain JavaScript:

const map = [
    0,0,1,1,
    1,1,1,1,
    1,1,1,1,
    1,1,1,1

]

Each tile is rendered as 128*128px square.

And I have written a function that prints out the euclidean distance between two points, in my case the distance between a click event on the tile map:

function distance(x,y,x2,y2) {
    return Math.sqrt(Math.pow((x-x2), 2)+Math.pow((y-y2), 2))
}

How do I calculate on which of the tiles the click occured?

Answer 1

If map represents a 4 x 4 matrix, you could calculate the index with the following formula.

 const getIndex = (x, y) => x + 4 * y, map = [0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]; console.log(getIndex(0, 0)); console.log(getIndex(1, 0));

Answer 2

supose you have a matrix nxm where n = number of rows m = number of columns

you will have a array with n * m values

So to calculate the euclidian distance of two points, you will need to know the horizontal (x) index and vertical (y) index of that value, for example:

map = [1, 1, 1, 1] 
// map[0] is in the position (0, 0)
// map[1] is in the position (1, 0)
// map[2] is in the position (0, 1)
// map[3] is in the position (1, 1)

You can do this using this function:

const getX = (index, m) => index % m
const getY = (index, n) => Math.floor(index / n)

now you can use your function:

let m = 128,
    n = 128,
    index = 0,
    index2 = 1,
    map = [// n * m values here],
    x, y, x1, y1

x = getX(index, m)
y = getY(index, n)
x1 = getX(index1, m)
y1 = getY(index1, n)

d = distance(x, y , x1, y1)