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Javascript 如何在不同的计算机上从第一台计算机绘制相同的线？

javascript html node.js canvas

Javascript 如何在不同的计算机上从第一台计算机绘制相同的线？,javascript,html,node.js,canvas,drawing,Javascript,Html,Node.js,Canvas,Drawing,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

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>
output.txt 这是我在Google Chrome上画了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
创建两个函数

一个用于读取JSON，另一个用于处理JSON

如果您还没有固化JSON，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，创建一个函数，该函数将在一个循环中完成此操作（我对此非常陌生，因此如果我做错了什么，我很抱歉）：

现在，我加入了另一个函数。使用包含的两个变量来绘制线。你已经为另一个客户做了，现在也做同样的事情

通过读取output.txt，我认为server.js可以将字符串发送给其他人，但不能从中提取。 
{
"action_type": "line",
"line_start_x": 1,
"line_start_y": 2,
"line_length": 4,
"line_end_x": 5,
"line_end_y": 6
}

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
}