javascript - 从 D3 转换后 Canvas 的定位

Question

我刚刚设法将相应的热图从 SVG 转换为 Canvas 。 (由于大数据集与性能问题)但是生成的热图的位置已经转到了一个新区域。我不确定我该怎么做。通过改变转换也不会改变任何东西。

我的代码:

var units = [];
for(var unit_i = 0; unit_i<=101;){
	if(unit_i==0){
	units.push(1);
	unit_i = unit_i + 5;
	}
	else{
	units.push(unit_i);
	unit_i = unit_i + 4;
	}
}
var	times = [];
for(var times_i = 0; times_i<=1440;){
	if(times_i==0){
	times.push(1);
	times_i = times_i + 10;
	}
	else{
	times.push(times_i);
	times_i = times_i + 9;
	}
}

var newSample = [{unit:null, timestamp: null, level: null}];


//by using below method we can observe the delay is not due to the data during insertion
for(var unit=1; unit<=99; unit++){
	for(var timestamp = 1; timestamp<=100; timestamp++){
		var i = Math.random() * 1400;
		newSample.push({unit:unit, timestamp: timestamp, level:i});
	}
}

var hours = 0;
var hoursIndicator = 0;
var margin = {
	top: 170,
	right: 100,
	bottom: 70,
	left: 100
};

var width = 2500,//optimized width
	//gridSize = Math.floor(width / times.length),//optimized gridsize
	gridSize = 10;//if 20 each interval will have 5
	height = 50 * (units.length); //optimized, the greater the length, the greater the height

console.log("this is gridSize:" + gridSize +", this is height: " + height + ", and this is width: " + width);

//SVG container
var svg = d3.select('.trafficCongestions')
	.append("svg")
	//.style("position", "absolute")
	.attr("width", width + margin.left + margin.right)//optimization
	.attr("height", height + margin.top + margin.bottom)//optimization
	.append("g")
	.attr("transform", "translate(" + margin.left + "," + margin.top + ")");


var canvas = d3.select('.trafficCongestions').append("canvas")
			   .attr("id", "canvas")
			   .attr("width", width + margin.left + margin.right)//optimization
	           .attr("height", height + margin.top + margin.bottom);//optimization

var context = canvas.node().getContext("2d");
context.clearRect(0, 0, width, height);

var detachedContainer = document.createElement("custom");
var dataContainer = d3.select(detachedContainer);

//Reset the overall font size
var newFontSize = width * 62.5 / 900;


//heatmap drawing starts from here
var colorScale = d3.scaleLinear()
	.domain([0, d3.max(newSample, function(d, i) {return d.level; })/2, d3.max(newSample, function(d, i) {return d.level; })])
	.range(["#009933", "#FFCC00", "#990000"])//obtain the max data value of count


//y-axis (solely based on data of days)
var dayLabels = svg.selectAll(".dayLabel")
    .data(units)
    .enter().append("text")
    .text(function (d) { return d; })
    .attr("x", 0)
    .attr("y", function (d, i) { 
    	return (i) * (gridSize * 4)/*adjusts the interval distance with (n - 1) concept*/; })
    .style("text-anchor", "end")
    .attr("transform", "translate(-6," + gridSize  + ")");

//x-axis (solely based on data of times)
var timeLabels = svg.selectAll(".timeLabel")
    .data(times)
    .enter().append("text")
    .text(function(d, i) {
    	var hrs = Math.floor(d/60);
  		var mins = d%60;
  			if(hrs<10){
    			if(mins<10){
      				return "0"+hrs + ":0" + mins;
    			}
    			return "0"+ hrs + ":" + mins;
  			}
  			return hrs +":"+ mins; 
  		})
    .attr("x", function(d, i) { return i * (gridSize * 9)/*adjusts the interval distance with (n - 1) concept*/; })
    .attr("y", 0)
    .style("text-anchor", "middle")
    .attr("transform", "translate(" + 1  + ", -6)")

	var heatMap = dataContainer.selectAll("custom.rect")
    .data(newSample)
    .enter().append("custom")
    .attr("x", function(d) { 
    	return (d.timestamp - 1) * (gridSize); 
    })
    .attr("y", function(d) { 
    	console.log(d.unit);
    	return (d.unit - 1) * (gridSize); 
    })
    .classed("rect", true)
    .attr("class", " rect bordered")
    .attr("width", gridSize)
    .attr("height", gridSize)
    .attr("strokeStyle", "rgba(255,255,255, 0.6)")//to have the middle line or not
    .attr("fillStyle", function(d,i){
    	return colorScale(d.level);
    });

    drawCanvas();


//Append title to the top
svg.append("text")
	.attr("class", "title")
    .attr("x", width/2)
    .attr("y", -90)
    .style("text-anchor", "middle")
    .text("Sample Result");
svg.append("text")
	.attr("class", "subtitle")
    .attr("x", width/2)
    .attr("y", -60)
    .style("text-anchor", "middle")
    .text("HEATMAP");

//Append credit at bottom
svg.append("text")
	.attr("class", "credit")
    .attr("x", width/2)
    .attr("y", gridSize * (units.length+1) + 80)
    .style("text-anchor", "middle");

//Extra scale since the color scale is interpolated
var countScale = d3.scaleLinear()
	.domain([0, d3.max(newSample, function(d) {return d.level; })])
	.range([0, width])

//Calculate the variables for the temp gradient
var numStops = 10;
countRange = countScale.domain();
countRange[2] = countRange[1] - countRange[0];
countPoint = [];
for(var i = 0; i < numStops; i++) {
	countPoint.push(i * countRange[2]/(numStops-1) + countRange[0]);
}//for i

//Create the gradient
svg.append("defs")
	.append("linearGradient")
	.attr("id", "legendLevel")
	.attr("x1", "0%").attr("y1", "0%")
	.attr("x2", "100%").attr("y2", "0%")
	.selectAll("stop") 
	.data(d3.range(numStops))                
	.enter().append("stop") 
	.attr("offset", function(d,i) { 
		return countScale( countPoint[i] )/width;
	})   
	.attr("stop-color", function(d,i) { 
		return colorScale( countPoint[i] ); 
	});

var legendWidth = Math.min(width, 400);//the width of the legend
console.log(width);
//Color Legend container
var legendsvg = svg.append("g")
	.attr("class", "legendWrapper")
	.attr("transform", "translate(" + (width/2) + "," + (gridSize * 100 + 40) + ")");

//Draw the Rectangle
legendsvg.append("rect")
	.attr("class", "legendRect")
	.attr("x", -legendWidth/2)
	.attr("y", 0)
	.attr("width", legendWidth)
	.attr("height", 10)
	.style("fill", "url(#legendLevel)");
	
//Append title
legendsvg.append("text")
	.attr("class", "legendTitle")
	.attr("x", 0)
	.attr("y", -10)
	.style("text-anchor", "middle")
	.text("Level");

//Set scale for x-axis
var xScale = d3.scaleLinear()
	 .range([-legendWidth/2, legendWidth/2])
	 .domain([ 0, d3.max(newSample, function(d) { return d.level; })] );

//Define x-axis
var xAxis = d3.axisBottom()
	  .ticks(5)
	  .scale(xScale);

//Set up X axis
legendsvg.append("g")
	.attr("class", "axis")
	.attr("transform", "translate(0," + (10) + ")")
	.call(xAxis);

function drawCanvas(){

	var elements = dataContainer.selectAll("custom.rect");

	elements.each(function(d){
		var node = d3.select(this);

		context.beginPath();
		context.fillStyle = node.attr("fillStyle");
		context.rect(node.attr("x"), node.attr("y"), node.attr("width"), node.attr("height"));
    	context.fill();
    	context.closePath();
	});
}

html { font-size: 100%; } 


    .timeLabel, .dayLabel {
        font-size: 1rem;
        fill: #AAAAAA;
        font-weight: 300;
    }

    .title {
        font-size: 1.8rem;
        fill: #4F4F4F;
        font-weight: 300;
    }

    .subtitle {
        font-size: 1.0rem;
        fill: #AAAAAA;
        font-weight: 300;
    }
      
    .credit {
        font-size: 1.2rem;
        fill: #AAAAAA;
        font-weight: 400;
    }

    .axis path, .axis tick, .axis line {
          fill: none;
          stroke: none;
      }  

    .legendTitle {
          font-size: 1.3rem;
          fill: #4F4F4F;
          font-weight: 300;

<script src="https://d3js.org/d3.v4.min.js"></script>
<div id="trafficCongestions" class="trafficCongestions"></div>

Answer 1

当您使用 svg 来显示 text 和 legend 时，我会说您可以绝对定位 Canvas SVG 的顶部 - 通过 CSS。

以下是 CSS 更改:

div#trafficCongestions {
  position: relative;
}
canvas {
  position: absolute;
  top: 170px;
  left: 100px;
}

您也可以使用 d3 样式 执行上述操作，因为 边距 是在脚本中定义的。我只是想表明这是一个可以使用的选项。

var units = [];
for(var unit_i = 0; unit_i<=101;){
	if(unit_i==0){
	units.push(1);
	unit_i = unit_i + 5;
	}
	else{
	units.push(unit_i);
	unit_i = unit_i + 4;
	}
}
var	times = [];
for(var times_i = 0; times_i<=1440;){
	if(times_i==0){
	times.push(1);
	times_i = times_i + 10;
	}
	else{
	times.push(times_i);
	times_i = times_i + 9;
	}
}

var newSample = [{unit:null, timestamp: null, level: null}];


//by using below method we can observe the delay is not due to the data during insertion
for(var unit=1; unit<=99; unit++){
	for(var timestamp = 1; timestamp<=100; timestamp++){
		var i = Math.random() * 1400;
		newSample.push({unit:unit, timestamp: timestamp, level:i});
	}
}

var hours = 0;
var hoursIndicator = 0;
var margin = {
	top: 170,
	right: 100,
	bottom: 70,
	left: 100
};

var width = 2500,//optimized width
	//gridSize = Math.floor(width / times.length),//optimized gridsize
	gridSize = 10;//if 20 each interval will have 5
	height = 50 * (units.length); //optimized, the greater the length, the greater the height

//console.log("this is gridSize:" + gridSize +", this is height: " + height + ", and this is width: " + width);

//SVG container
var svg = d3.select('.trafficCongestions')
	.append("svg")
	//.style("position", "absolute")
	.attr("width", width + margin.left + margin.right)//optimization
	.attr("height", height + margin.top + margin.bottom)//optimization
	.append("g")
	.attr("transform", "translate(" + margin.left + "," + margin.top + ")");


var canvas = d3.select('.trafficCongestions').append("canvas")
			   .attr("id", "canvas")
			   .attr("width", width + margin.left + margin.right)//optimization
	           .attr("height", height + margin.top + margin.bottom);//optimization

var context = canvas.node().getContext("2d");
context.clearRect(0, 0, width, height);

var detachedContainer = document.createElement("custom");
var dataContainer = d3.select(detachedContainer);

//Reset the overall font size
var newFontSize = width * 62.5 / 900;


//heatmap drawing starts from here
var colorScale = d3.scaleLinear()
	.domain([0, d3.max(newSample, function(d, i) {return d.level; })/2, d3.max(newSample, function(d, i) {return d.level; })])
	.range(["#009933", "#FFCC00", "#990000"])//obtain the max data value of count


//y-axis (solely based on data of days)
var dayLabels = svg.selectAll(".dayLabel")
    .data(units)
    .enter().append("text")
    .text(function (d) { return d; })
    .attr("x", 0)
    .attr("y", function (d, i) { 
    	return (i) * (gridSize * 4)/*adjusts the interval distance with (n - 1) concept*/; })
    .style("text-anchor", "end")
    .attr("transform", "translate(-6," + gridSize  + ")");

//x-axis (solely based on data of times)
var timeLabels = svg.selectAll(".timeLabel")
    .data(times)
    .enter().append("text")
    .text(function(d, i) {
    	var hrs = Math.floor(d/60);
  		var mins = d%60;
  			if(hrs<10){
    			if(mins<10){
      				return "0"+hrs + ":0" + mins;
    			}
    			return "0"+ hrs + ":" + mins;
  			}
  			return hrs +":"+ mins; 
  		})
    .attr("x", function(d, i) { return i * (gridSize * 9)/*adjusts the interval distance with (n - 1) concept*/; })
    .attr("y", 0)
    .style("text-anchor", "middle")
    .attr("transform", "translate(" + 1  + ", -6)")

	var heatMap = dataContainer.selectAll("custom.rect")
    .data(newSample)
    .enter().append("custom")
    .attr("x", function(d) { 
    	return (d.timestamp - 1) * (gridSize); 
    })
    .attr("y", function(d) { 
    	//console.log(d.unit);
    	return (d.unit - 1) * (gridSize); 
    })
    .classed("rect", true)
    .attr("class", " rect bordered")
    .attr("width", gridSize)
    .attr("height", gridSize)
    .attr("strokeStyle", "rgba(255,255,255, 0.6)")//to have the middle line or not
    .attr("fillStyle", function(d,i){
    	return colorScale(d.level);
    });

    drawCanvas();


//Append title to the top
svg.append("text")
	.attr("class", "title")
    .attr("x", width/2)
    .attr("y", -90)
    .style("text-anchor", "middle")
    .text("Sample Result");
svg.append("text")
	.attr("class", "subtitle")
    .attr("x", width/2)
    .attr("y", -60)
    .style("text-anchor", "middle")
    .text("HEATMAP");

//Append credit at bottom
svg.append("text")
	.attr("class", "credit")
    .attr("x", width/2)
    .attr("y", gridSize * (units.length+1) + 80)
    .style("text-anchor", "middle");

//Extra scale since the color scale is interpolated
var countScale = d3.scaleLinear()
	.domain([0, d3.max(newSample, function(d) {return d.level; })])
	.range([0, width])

//Calculate the variables for the temp gradient
var numStops = 10;
countRange = countScale.domain();
countRange[2] = countRange[1] - countRange[0];
countPoint = [];
for(var i = 0; i < numStops; i++) {
	countPoint.push(i * countRange[2]/(numStops-1) + countRange[0]);
}//for i

//Create the gradient
svg.append("defs")
	.append("linearGradient")
	.attr("id", "legendLevel")
	.attr("x1", "0%").attr("y1", "0%")
	.attr("x2", "100%").attr("y2", "0%")
	.selectAll("stop") 
	.data(d3.range(numStops))                
	.enter().append("stop") 
	.attr("offset", function(d,i) { 
		return countScale( countPoint[i] )/width;
	})   
	.attr("stop-color", function(d,i) { 
		return colorScale( countPoint[i] ); 
	});

var legendWidth = Math.min(width, 400);//the width of the legend
//console.log(width);
//Color Legend container
var legendsvg = svg.append("g")
	.attr("class", "legendWrapper")
	.attr("transform", "translate(" + (width/2) + "," + (gridSize * 100 + 40) + ")");

//Draw the Rectangle
legendsvg.append("rect")
	.attr("class", "legendRect")
	.attr("x", -legendWidth/2)
	.attr("y", 0)
	.attr("width", legendWidth)
	.attr("height", 10)
	.style("fill", "url(#legendLevel)");
	
//Append title
legendsvg.append("text")
	.attr("class", "legendTitle")
	.attr("x", 0)
	.attr("y", -10)
	.style("text-anchor", "middle")
	.text("Level");

//Set scale for x-axis
var xScale = d3.scaleLinear()
	 .range([-legendWidth/2, legendWidth/2])
	 .domain([ 0, d3.max(newSample, function(d) { return d.level; })] );

//Define x-axis
var xAxis = d3.axisBottom()
	  .ticks(5)
	  .scale(xScale);

//Set up X axis
legendsvg.append("g")
	.attr("class", "axis")
	.attr("transform", "translate(0," + (10) + ")")
	.call(xAxis);

function drawCanvas(){

	var elements = dataContainer.selectAll("custom.rect");

	elements.each(function(d){
		var node = d3.select(this);

		context.beginPath();
		context.fillStyle = node.attr("fillStyle");
		context.rect(node.attr("x"), node.attr("y"), node.attr("width"), node.attr("height"));
    	context.fill();
    	context.closePath();
	});
}

html { font-size: 100%; } 

div#trafficCongestions {
  position: relative;
}
canvas {
  position: absolute;
  top: 170px;
  left: 100px;
}
    .timeLabel, .dayLabel {
        font-size: 1rem;
        fill: #AAAAAA;
        font-weight: 300;
    }

    .title {
        font-size: 1.8rem;
        fill: #4F4F4F;
        font-weight: 300;
    }

    .subtitle {
        font-size: 1.0rem;
        fill: #AAAAAA;
        font-weight: 300;
    }
      
    .credit {
        font-size: 1.2rem;
        fill: #AAAAAA;
        font-weight: 400;
    }

    .axis path, .axis tick, .axis line {
          fill: none;
          stroke: none;
      }  

    .legendTitle {
          font-size: 1.3rem;
          fill: #4F4F4F;
          font-weight: 300;
     }

<script src="https://d3js.org/d3.v4.min.js"></script>
<div id="trafficCongestions" class="trafficCongestions"></div>

让我知道这是否有意义。如果没有，让我们寻找其他方法。

根据评论编辑:(visual studio 不支持通过上述方法添加的 CSS 样式)

使用 d3 添加样式:

canvas.style('position', 'absolute').style('top', margin.top+'px').style('left', margin.left+'px')

这成功了。