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D3：SVG中的缩放/平移线图在Canvas中不起作用

[英]D3: Zooming/Panning Line Graph in SVG is not working in Canvas

 原文  2017-08-23 15:28:50  9   2    javascript/ d3.js/ canvas/ svg

问题描述

我使用SVG创建了d3 zooming/panning图。 我正在尝试使用Canvas创建相同的图形。 我的问题是，当涉及到Canvas图的缩放和平移时，图表正在消失，我无法弄清楚原因。 我创建了两个JSBin来显示两者的代码。 有人可以帮助我。

SVG - JSBin

画布 - JSBin

我的SVG缩放代码如下所示： 

// Zoom Components
zoom = d3.zoom()
        .scaleExtent([1, dayDiff*12])
        .translateExtent([[0, 0], [width, height]])
        .extent([[0, 0], [width, height]])
        .on("zoom", zoomed);

function zoomed(){
    t = d3.event.transform;
    xScale.domain(t.rescaleX(x2).domain());
    xAxis = d3.axisBottom(xScale).tickSize(0).tickFormat(d3.timeFormat('%b'));
    focus.select(".axis--x").call(xAxis); //xAxis changes
    usageLinePath.attr('d',line); //line path reference, regenerate
}

我的Canvas缩放代码如下所示： 

// Zoom Components
zoom = d3.zoom()
        .scaleExtent([1, dayDiff*12])
        .translateExtent([[0, 0], [width, height]])
        .extent([[0, 0], [width, height]])
        .on("zoom", zoomed);

function zoomed() {
    t = d3.event.transform;
    x.domain(t.rescaleX(x2).domain());
    context.save();
    context.clearRect(0, 0, width, height);
    draw();
    context.restore();
}

function draw() {
    xAxis();
    yAxis();

    context.beginPath();
    line(data);
    context.lineWidth = 1.5;
    context.strokeStyle = "steelblue";
    context.stroke();
}

2 个解决方案

解决方案1
 5 已采纳  2017-08-25 19:13:23

有一个主要的悲伤源导致你的线消失，它只在缩放时触发： 

function zoomed() {
    t = d3.event.transform;
    x.domain(t.rescaleX(x2).domain());  // here
    ...
}

由于您尚未定义其域，因此重新缩放将无法在x2 。 x2是用于在每次缩放时设置x参考比例，它应该与x一样开始。 但是， d3.timeScale()的默认域是2000年1月1日到2000年1月2日（请参阅API文档 ），由于您的数据与此期间不重叠，因此无法确定您的数据。

您需要设置x2和x的域。 如果在使用x2.domain(x.domain())设置x的初始域后执行此操作，则应获得一个更新（ jsbin ）的图表，因为现在您拥有一个与您的数据重叠的域。

但是，现在问题是你需要剪切你的行，你在你的svg例子中而不是画布。 为此，您可以使用以下内容： 

function draw() {
    xAxis();
    yAxis();

  // save context without clip apth
  context.save();

  // create a clip path:
  context.beginPath()
  context.rect(0, 0, width, height);
  context.clip();

  // draw line in clip path
  context.beginPath()
  line(data);

  context.lineWidth = 1.5;
  context.strokeStyle = "steelblue";
  context.stroke();

  // restore context without clip path
  context.restore();
}

看到这个jsbin

因为我们不应该让轴自己覆盖：这是一个擦除前一个轴的jsbin （带有注释掉的代码块，根据所选x域中包含的值重新定义y域）。

为了更好地衡量，这里是最后一个jsbin的片段（缩小为片段视图）： 

 var data = getData().map(function (d) { return d; }); var canvas = document.querySelector("canvas"), context = canvas.getContext("2d"); var margin = { top: 20, right: 20, bottom: 30, left: 50 }, width = canvas.width - margin.left - margin.right, height = canvas.height - margin.top - margin.bottom; var parseTime = d3.timeParse("%d-%b-%y"); // setup scales var x = d3.scaleTime() .range([0, width]); var x2 = d3.scaleTime().range([0, width]); var y = d3.scaleLinear() .range([height, 0]); // setup domain x.domain(d3.extent(data, function (d) { return moment(d.Ind, 'YYYYMM'); })); y.domain(d3.extent(data, function (d) { return d.KSum; })); x2.domain(x.domain()); // get day range var dayDiff = daydiff(x.domain()[0],x.domain()[1]); // line generator var line = d3.line() .x(function (d) { return x(moment(d.Ind, 'YYYYMM')); }) .y(function (d) { return y(d.KSum); }) .curve(d3.curveMonotoneX) .context(context); // zoom var zoom = d3.zoom() .scaleExtent([1, dayDiff]) .translateExtent([[0, 0], [width, height]]) .extent([[0, 0], [width, height]]) .on("zoom", zoomed); d3.select("canvas").call(zoom) context.translate(margin.left, margin.top); draw(); // function draw() { // remove everything: context.clearRect(-margin.left, -margin.top, canvas.width, canvas.height); /* // Calculate the y axis domain across the selected x domain: newYDomain = d3.extent(data, function(d) { if ( (x(moment(d.Ind, 'YYYYMM')) > 0) && (x(moment(d.Ind, 'YYYYMM')) < width) ) { return d.KSum; } }); // Don't update the y axis if there are no points to set a new domain, just keep the old domain. if ((newYDomain[0] !== undefined) && (newYDomain[0] != newYDomain[1])) { y.domain(newYDomain); } //*/ // draw axes: xAxis(); yAxis(); // save context without clip apth context.save(); // create a clip path: context.beginPath() context.rect(0, 0, width, height); context.clip(); // draw line in clip path context.beginPath() line(data); context.lineWidth = 1.5; context.strokeStyle = "steelblue"; context.stroke(); // restore context without clip path context.restore(); } function zoomed() { t = d3.event.transform; x.domain(t.rescaleX(x2).domain()); draw(); } function xAxis() { var tickCount = 10, tickSize = 6, ticks = x.ticks(tickCount), tickFormat = x.tickFormat(); context.beginPath(); ticks.forEach(function (d) { context.moveTo(x(d), height); context.lineTo(x(d), height + tickSize); }); context.strokeStyle = "black"; context.stroke(); context.textAlign = "center"; context.textBaseline = "top"; ticks.forEach(function (d) { context.fillText(tickFormat(d), x(d), height + tickSize); }); } function yAxis() { var tickCount = 10, tickSize = 6, tickPadding = 3, ticks = y.ticks(tickCount), tickFormat = y.tickFormat(tickCount); context.beginPath(); ticks.forEach(function (d) { context.moveTo(0, y(d)); context.lineTo(-6, y(d)); }); context.strokeStyle = "black"; context.stroke(); context.beginPath(); context.moveTo(-tickSize, 0); context.lineTo(0.5, 0); context.lineTo(0.5, height); context.lineTo(-tickSize, height); context.strokeStyle = "black"; context.stroke(); context.textAlign = "right"; context.textBaseline = "middle"; ticks.forEach(function (d) { context.fillText(tickFormat(d), -tickSize - tickPadding, y(d)); }); context.save(); context.rotate(-Math.PI / 2); context.textAlign = "right"; context.textBaseline = "top"; context.font = "bold 10px sans-serif"; context.fillText("Price (US$)", -10, 10); context.restore(); } function getDate(d) { return new Date(d.Ind); } function daydiff(first, second) { return Math.round((second - first) / (1000 * 60 * 60 * 24)); } function getData() { return [ { "BriteID": "BI-43dd32fe-ecbc-48d4-a8dc-e1f66110a542", "Ind": 201501, "TMin": 30.43, "TMax": 77.4, "KMin": 0.041, "KMax": 1.364, "KSum": 625.08 }, { "BriteID": "BI-43dd32fe-ecbc-48d4-a8dc-e1f66110a542", "Ind": 201502, "TMin": 35.3, "TMax": 81.34, "KMin": 0.036, "KMax": 1.401, "KSum": 542.57 }, { "BriteID": "BI-43dd32fe-ecbc-48d4-a8dc-e1f66110a542", "Ind": 201503, "TMin": 32.58, "TMax": 81.32, "KMin": 0.036, "KMax": 1.325, "KSum": 577.83 }, { "BriteID": "BI-43dd32fe-ecbc-48d4-a8dc-e1f66110a542", "Ind": 201504, "TMin": 54.54, "TMax": 86.55, "KMin": 0.036, "KMax": 1.587, "KSum": 814.62 }, { "BriteID": "BI-43dd32fe-ecbc-48d4-a8dc-e1f66110a542", "Ind": 201505, "TMin": 61.35, "TMax": 88.61, "KMin": 0.036, "KMax": 1.988, "KSum": 2429.56 }, { "BriteID": "BI-43dd32fe-ecbc-48d4-a8dc-e1f66110a542", "Ind": 201506, "TMin": 69.5, "TMax": 92.42, "KMin": 0.037, "KMax": 1.995, "KSum": 2484.93 }, { "BriteID": "BI-43dd32fe-ecbc-48d4-a8dc-e1f66110a542", "Ind": 201507, "TMin": 71.95, "TMax": 98.62, "KMin": 0.037, "KMax": 1.864, "KSum": 2062.05 }, { "BriteID": "BI-43dd32fe-ecbc-48d4-a8dc-e1f66110a542", "Ind": 201508, "TMin": 76.13, "TMax": 99.59, "KMin": 0.045, "KMax": 1.977, "KSum": 900.05 }, { "BriteID": "BI-43dd32fe-ecbc-48d4-a8dc-e1f66110a542", "Ind": 201509, "TMin": 70, "TMax": 91.8, "KMin": 0.034, "KMax": 1.458, "KSum": 401.39 }]; } 
 <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.10.0/d3.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.18.1/moment.js"></script> <canvas width="500" height="200"></canvas>

解决方案2
 2  2017-08-25 20:01:05

每次绘制时都需要清除画布，只需在draw函数中添加， 

context.clearRect(0-margin.left, 0, canvas.width, canvas.height);

其余的是， 

var data = getData().map(function (d) {
            return d;
        });

        var canvas = document.querySelector("canvas"),
            context = canvas.getContext("2d");

        var margin = { top: 20, right: 20, bottom: 30, left: 50 },
            width = canvas.width - margin.left - margin.right,
            height = canvas.height - margin.top - margin.bottom;

        var parseTime = d3.timeParse("%d-%b-%y");

        // setup scales
        var x = d3.scaleTime()
            .range([0, width]);
        var x2 = d3.scaleTime().range([0, width]);
        var y = d3.scaleLinear()
            .range([height, 0]);

        // setup domain
        x.domain(d3.extent(data, function (d) { return moment(d.Ind, 'YYYYMM'); }));
        y.domain(d3.extent(data, function (d) { return d.KSum; }));
        x2.domain(x.domain());

        // get day range
        var dayDiff = daydiff(x.domain()[0],x.domain()[1]);

        // line generator
        var line = d3.line()
            .x(function (d) { return x(moment(d.Ind, 'YYYYMM')); })
            .y(function (d) { return y(d.KSum); })
            .curve(d3.curveMonotoneX)
            .context(context);

        // zoom
        var zoom = d3.zoom()
            .scaleExtent([1, dayDiff * 12])
            .translateExtent([[0, 0], [width, height]])
            .extent([[0, 0], [width, height]])
            .on("zoom", zoomed);

        d3.select("canvas").call(zoom)

        context.translate(margin.left, margin.top);

        draw();


        function draw() {
            context.clearRect(0-margin.left, 0, canvas.width, canvas.height);
            xAxis();
            yAxis();

            context.beginPath();
            line(data);
            context.lineWidth = 1.5;
            context.strokeStyle = "steelblue";
            context.stroke();
        }

        function zoomed() {
            console.log(d3.event);
            t = d3.event.transform;
            x.domain(t.rescaleX(x2).domain());
            context.save();
            context.clearRect(0, 0, width, height);
            // context.translate(d3.event.translate[0], d3.event.translate[1]);
            // context.scale(d3.event.scale, d3.event.scale);
            draw();
            context.restore();
        }

        function xAxis() {
            var tickCount = 10,
                tickSize = 6,
                ticks = x.ticks(tickCount),
                tickFormat = x.tickFormat();

            context.beginPath();
            ticks.forEach(function (d) {
                context.moveTo(x(d), height);
                context.lineTo(x(d), height + tickSize);
            });
            context.strokeStyle = "black";
            context.stroke();

            context.textAlign = "center";
            context.textBaseline = "top";
            ticks.forEach(function (d) {
                context.fillText(tickFormat(d), x(d), height + tickSize);
            });
        }

        function yAxis() {
            var tickCount = 10,
                tickSize = 6,
                tickPadding = 3,
                ticks = y.ticks(tickCount),
                tickFormat = y.tickFormat(tickCount);

            context.beginPath();
            ticks.forEach(function (d) {
                context.moveTo(0, y(d));
                context.lineTo(-6, y(d));
            });
            context.strokeStyle = "black";
            context.stroke();

            context.beginPath();
            context.moveTo(-tickSize, 0);
            context.lineTo(0.5, 0);
            context.lineTo(0.5, height);
            context.lineTo(-tickSize, height);
            context.strokeStyle = "black";
            context.stroke();

            context.textAlign = "right";
            context.textBaseline = "middle";
            ticks.forEach(function (d) {
                context.fillText(tickFormat(d), -tickSize - tickPadding, y(d));
            });

            context.save();
            context.rotate(-Math.PI / 2);
            context.textAlign = "right";
            context.textBaseline = "top";
            context.font = "bold 10px sans-serif";
            context.fillText("Price (US$)", -10, 10);
            context.restore();
        }

        function getDate(d) {
            return new Date(d.Ind);
        }

        function daydiff(first, second) {
            return Math.round((second - first) / (1000 * 60 * 60 * 24));
        }

        function getData() {
            return [
                {
                    "BriteID": "BI-43dd32fe-ecbc-48d4-a8dc-e1f66110a542",
                    "Ind": 201501,
                    "TMin": 30.43,
                    "TMax": 77.4,
                    "KMin": 0.041,
                    "KMax": 1.364,
                    "KSum": 625.08
                },
                {
                    "BriteID": "BI-43dd32fe-ecbc-48d4-a8dc-e1f66110a542",
                    "Ind": 201502,
                    "TMin": 35.3,
                    "TMax": 81.34,
                    "KMin": 0.036,
                    "KMax": 1.401,
                    "KSum": 542.57
                },
                {
                    "BriteID": "BI-43dd32fe-ecbc-48d4-a8dc-e1f66110a542",
                    "Ind": 201503,
                    "TMin": 32.58,
                    "TMax": 81.32,
                    "KMin": 0.036,
                    "KMax": 1.325,
                    "KSum": 577.83
                },
                {
                    "BriteID": "BI-43dd32fe-ecbc-48d4-a8dc-e1f66110a542",
                    "Ind": 201504,
                    "TMin": 54.54,
                    "TMax": 86.55,
                    "KMin": 0.036,
                    "KMax": 1.587,
                    "KSum": 814.62
                },
                {
                    "BriteID": "BI-43dd32fe-ecbc-48d4-a8dc-e1f66110a542",
                    "Ind": 201505,
                    "TMin": 61.35,
                    "TMax": 88.61,
                    "KMin": 0.036,
                    "KMax": 1.988,
                    "KSum": 2429.56
                },
                {
                    "BriteID": "BI-43dd32fe-ecbc-48d4-a8dc-e1f66110a542",
                    "Ind": 201506,
                    "TMin": 69.5,
                    "TMax": 92.42,
                    "KMin": 0.037,
                    "KMax": 1.995,
                    "KSum": 2484.93
                },
                {
                    "BriteID": "BI-43dd32fe-ecbc-48d4-a8dc-e1f66110a542",
                    "Ind": 201507,
                    "TMin": 71.95,
                    "TMax": 98.62,
                    "KMin": 0.037,
                    "KMax": 1.864,
                    "KSum": 2062.05
                },
                {
                    "BriteID": "BI-43dd32fe-ecbc-48d4-a8dc-e1f66110a542",
                    "Ind": 201508,
                    "TMin": 76.13,
                    "TMax": 99.59,
                    "KMin": 0.045,
                    "KMax": 1.977,
                    "KSum": 900.05
                },
                {
                    "BriteID": "BI-43dd32fe-ecbc-48d4-a8dc-e1f66110a542",
                    "Ind": 201509,
                    "TMin": 70,
                    "TMax": 91.8,
                    "KMin": 0.034,
                    "KMax": 1.458,
                    "KSum": 401.39
                }];
        }

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