javascript - 确定 Canvas 网格的单元格 x 和 y

Question

我有一个nodejs应用程序，它在当前使用for循环的 Canvas 中创建一个网格。我需要帮助编写一个算法来确定我的光标当前在 x 和 y 方向上的哪个单元格。网格当前为 25x25，我正在跟踪 Canvas 内的鼠标移动。我不想给我原始的 x 和 y 鼠标坐标，而是想要一个单元格坐标。有什么帮助吗？谢谢!

//START {EXPRESS}
var express = require('express');
var app = express();
var serv = require('http').Server(app);
 
app.get('/',function(req, res) {
    res.sendFile(__dirname + '/client/index.html');
});
app.use('/client',express.static(__dirname + '/client'));
 
serv.listen(2000);
console.log("Server started.");


var io = require('socket.io')(serv,{});
io.sockets.on('connection', function(socket){
	//RETRIEVING THE MOUSE X AND Y COORDINATES
	socket.on('mouseMove', function(data){
		console.log(data.x + ", " + data.y);
	});

});

<div id="gameDiv">
	<center>
	<canvas id="ctx" width="750" height="750" style="border:1px solid #000000;"></canvas>
	</center>
</div>
	
<script src="https://cdn.socket.io/socket.io-1.4.5.js"></script>
	
<script>
	//NETWORK VARIABLES
	var socket = io();
	//GETTING THE CANVAS BY ID
	var canvas = document.getElementById("ctx");
	context = canvas.getContext("2d");
	
	//GRID VARIABLES
	var w=30,
	h=30,
	row=25,
	col=25,
	x=0,
	y=0;
	
	//LOOP TO DRAW THE GRID
	for(x=0; x<row; x++){
		for(y=0; y<col; y++){
			context.strokeRect(w*x,h*y,w,h);
		}
	}
	
	//GETTING THE MOUSE X AND Y
	function getMousePos(canvas, event){
		var rect = canvas.getBoundingClientRect();
		return {
			x:event.clientX - rect.left,
			y:event.clientY - rect.top
		};
	}
	
	canvas.addEventListener('mousemove', function(event){
		var pos = getMousePos(canvas, event);
		var posx = pos.x;
		var posy = pos.y;
		
        socket.emit('mouseMove',{x:x, y:y});
	}, false);
	
	
	
</script>

</html>

Answer 1

啊，我最终自己弄清楚了。

算法是 posx/height 四舍五入posy/宽度向上取整

这是 html

<div id="gameDiv">
	<center>
	<canvas id="ctx" width="750" height="750" style="border:1px solid #000000;"></canvas>
	</center>
</div>
	
<script src="https://cdn.socket.io/socket.io-1.4.5.js"></script>
	
<script>
	//NETWORK VARIABLES
	var socket = io();
	//GETTING THE CANVAS BY ID
	var canvas = document.getElementById("ctx");
	context = canvas.getContext("2d");
	
	//GRID VARIABLES
	var w=30,
	h=30,
	row=25,
	col=25,
	x=0,
	y=0,
	cX=0,
	cY=0;
	
	//LOOP TO DRAW THE GRID
	for(x=0; x<row; x++){
		for(y=0; y<col; y++){
			context.strokeRect(w*x,h*y,w,h);
		}
	}
	
	//GETTING THE MOUSE X AND Y
	function getMousePos(canvas, event){
		var rect = canvas.getBoundingClientRect();
		return {
			x:event.clientX - rect.left,
			y:event.clientY - rect.top
		};
	}
	
	canvas.addEventListener('mousemove', function(event){
		
		var pos = getMousePos(canvas, event);
		var posx = pos.x;
		var posy = pos.y;
		
		**cX = Math.ceil(posx/30);
		cY = Math.ceil(posy/30);**
		
        socket.emit('mouseMove',{x:cX, y:cY});
	}, false);