如何在另一台计算机上从第一台计算机绘制相同的线？ [关闭]答案

【问题标题】：How can I draw the same lines from the first computer on a different computer? [closed]如何在另一台计算机上从第一台计算机绘制相同的线？ [关闭]
【发布时间】：2014-01-19 21:51:54
【问题描述】：

我正在开发一个绘图应用程序。 HTML 代码是客户端，server.js 是服务器。我使用 node.js 和 socket.io 作为连接

index.html

<html>
<head>
    <script src="http://localhost:4000/socket.io/socket.io.js"></script>
<script>
      var socket = io.connect('http://localhost:4000');
    </script>

<script>
var canvas, ctx, flag = false,
    prevX = 0,
    currX = 0,
    prevY = 0,
    currY = 0,
    dot_flag = false;

var x = "black",
    y = 2;

function init() {
    canvas = document.getElementById('can');
    ctx = canvas.getContext("2d");
    w = canvas.width;
    h = canvas.height;

    canvas.addEventListener("mousemove", function (e) {
        findxy('move', e)
    }, false);
    canvas.addEventListener("mousedown", function (e) {
        findxy('down', e)
    }, false);
    canvas.addEventListener("mouseup", function (e) {
        findxy('up', e)
    }, false);
    canvas.addEventListener("mouseout", function (e) {
        findxy('out', e)
    }, false);
}

function draw() {
    ctx.beginPath();
    ctx.moveTo(prevX, prevY);
    ctx.lineTo(currX, currY);
    ctx.strokeStyle = x;
    ctx.lineWidth = y;
    ctx.stroke();
    ctx.closePath();

    var segment = {
    startX:prevX, 
    startY:prevY, 
    endX:currX, 
    endY:currY, 
    color:x, 
    linewidth:y
};

var segmentJSON = JSON.stringify(segment);

socket.emit('drawcanvas',segmentJSON);
socket.on('serverdrawcanvas',function(data)
{drawFromOtherComputer(data);});

}

function erase() {
    var m = confirm("Want to clear");
    if (m) {
        ctx.clearRect(0, 0, w, h);
    }
}

function findxy(res, e) {
    if (res == 'down') {
        prevX = currX;
        prevY = currY;
        currX = e.clientX - canvas.offsetLeft;
        currY = e.clientY - canvas.offsetTop;

        flag = true;
        dot_flag = true;
        if (dot_flag) {
            ctx.beginPath();
            ctx.fillStyle = x;
            ctx.fillRect(currX, currY, 2, 2);
            ctx.closePath();
            dot_flag = false;
        }
    }
    if (res == 'up' || res == "out") {
        flag = false;
    }
    if (res == 'move') {
        if (flag) {
            prevX = currX;
            prevY = currY;
            currX = e.clientX - canvas.offsetLeft;
            currY = e.clientY - canvas.offsetTop;
            draw();
        }
    }
}
function drawFromOtherComputer(segmentJSON) {
    var segment = JSON.parse(segmentJSON);
    ctx.beginPath();
    ctx.moveTo(segment.startingX, segment.startingY);
    ctx.lineTo(segment.endingX, segment.endingY);
    ctx.strokeStyle = segment.color;
    ctx.lineWidth = segment.linewidth;
    ctx.stroke();
}

</script>
</head>
<body onload="init()">
    <canvas id="can" width="400" height="400" style="position:absolute;top:10%;left:10%;border:2px solid;"></canvas>
    <input type="button" value="clear" id="clr" size="23" onclick="erase()" style="position:absolute;top:80%;left:15%;">
</body>
</html>

server.js

var httpd = require('http').createServer(handler);
var io = require('socket.io').listen(httpd);
var fs = require('fs');

httpd.listen(4000);

function handler(req, res) {
  fs.readFile(__dirname + '/index.html',
    function(err, data) {
      if (err) {
       res.writeHead(500);
       return res.end('Error loading index.html');
      }

      res.writeHead(200);
      res.end(data);
    }
  );
}
io.sockets.on('connection', function (socket) {
    socket.on('drawcanvas', function(segmentjson){
    socket.emit('serverdrawcanvas', segmentjson);
  });
});

输出.txt 这是我在谷歌浏览器上画一条小线后得到的日志文件

info: socket.io started
debug: served static content /socket.io.js
debug: client authorized
info: handshake authorized nvbhnJFo-BL7xL09u9PY
debug: setting request GET /socket.io/1/websocket/nvbhnJFo-BL7xL09u9PY
debug: set heartbeat interval for client nvbhnJFo-BL7xL09u9PY
debug: client authorized for 
debug: websocket writing 1::
debug: websocket writing 5:::{"name":"serverdrawcanvas","args":["{\"startX\":145,\"startY\":40,\"endX\":146,\"endY\":40,\"color\":\"black\",\"linewidth\":2}"]}
debug: websocket writing 5:::{"name":"serverdrawcanvas","args":["{\"startX\":146,\"startY\":40,\"endX\":147,\"endY\":41,\"color\":\"black\",\"linewidth\":2}"]}
debug: websocket writing 5:::{"name":"serverdrawcanvas","args":["{\"startX\":147,\"startY\":41,\"endX\":148,\"endY\":41,\"color\":\"black\",\"linewidth\":2}"]}
debug: emitting heartbeat for client nvbhnJFo-BL7xL09u9PY
debug: websocket writing 2::
debug: set heartbeat timeout for client nvbhnJFo-BL7xL09u9PY
debug: got heartbeat packet
debug: cleared heartbeat timeout for client nvbhnJFo-BL7xL09u9PY
debug: set heartbeat interval for client nvbhnJFo-BL7xL09u9PY

【问题讨论】：

通过读取 output.txt，我认为 server.js 能够将字符串发送给其他人，但无法从中提取。

标签： javascript html node.js canvas drawing

【解决方案1】：

创建两个函数。

一个用来读取您的 JSON，另一个用来处理它。

如果您的 JSON 还没有固化，它可能看起来像这样：

{
"action_type": "line",
"line_start_x": 1,
"line_start_y": 2,
"line_length": 4,
"line_end_x": 5,
"line_end_y": 6
}

然后，创建一个循环执行此操作的函数（我对此很陌生，所以如果我做错了什么，我很抱歉）：

while(actions = your_json_var['action_type']) {
drawPeerLine(your_json_var['line_start_x'], your_json_var['line_start_y']); // Keep adding in the varibles you need
}

现在，我在那里添加了另一个函数。使用两个包含的变量来画线。您已经为其他客户完成了此操作，现在只需执行相同操作即可。

【讨论】：