Chart.js 折线图设置背景色 [英] Chart.js line chart set background color
问题描述
我正在使用 Chart.js 并想将折线图转换为 PNG.问题是图像总是以透明背景下载,这不是我需要的.我尝试了很多选择,但没有任何效果.
和建议?
这是获得完全不透明版本的 ChartJS 的一种方法:
等待图表完全动画化并完成.您可以通过将 onAnimationComplete
属性添加到图表来实现这一点.
在onAnimationComplete
函数中:
- 在内存中创建一个与图表大小相同的临时画布.
- 用白色填充临时画布
drawImage
白色填充临时画布上的 ChartJS 画布- 从临时画布创建图像.
可能的做法如下:
var ctx = document.getElementById("canvas").getContext("2d");window.myLine = new Chart(ctx).Line(lineChartData, {响应:真实,onAnimationComplete:function(){var tcanvas=document.createElement('canvas');var tctx=tcanvas.getContext('2d');tcanvas.width=ctx.canvas.width;tcanvas.height=ctx.canvas.height;tctx.fillStyle='白';tctx.fillRect(0,0,tcanvas.width,tcanvas.height);tctx.drawImage(canvas,0,0);var img=new Image();img.onload=function(){document.body.appendChild(img);}img.src=tcanvas.toDataURL();}});
这是示例代码和演示:
var randomScalingFactor = function(){ return Math.round(Math.random()*100)};var randomColorFactor = function(){ return Math.round(Math.random()*255)};var lineChartData = {标签:[一月"、二月"、三月"、四月"、五月"、六月"、七月"]、数据集:[{标签:我的第一个数据集",fillColor : "rgba(220,220,220,0.2)",strokeColor : "rgba(220,220,220,1)",pointColor : "rgba(220,220,220,1)",pointStrokeColor : "#fff",pointHighlightFill : "#fff",pointHighlightStroke : "rgba(220,220,220,1)",数据:[randomScalingFactor(),randomScalingFactor(),randomScalingFactor(),randomScalingFactor(),randomScalingFactor(),randomScalingFactor(),randomScalingFactor()]},{标签:我的第二个数据集",fillColor : "rgba(151,187,205,0.2)",strokeColor : "rgba(151,187,205,1)",pointColor : "rgba(151,187,205,1)",pointStrokeColor : "#fff",pointHighlightFill : "#fff",pointHighlightStroke : "rgba(151,187,205,1)",数据:[randomScalingFactor(),randomScalingFactor(),randomScalingFactor(),randomScalingFactor(),randomScalingFactor(),randomScalingFactor(),randomScalingFactor()]}]}var ctx = document.getElementById("canvas").getContext("2d");window.myLine = new Chart(ctx).Line(lineChartData, {响应:真实,onAnimationComplete:function(){var tcanvas=document.createElement('canvas');var tctx=tcanvas.getContext('2d');tcanvas.width=ctx.canvas.width;tcanvas.height=ctx.canvas.height;tctx.fillStyle='白';tctx.fillRect(0,0,tcanvas.width,tcanvas.height);tctx.drawImage(canvas,0,0);var img=new Image();img.onload=function(){document.body.appendChild(img);}img.src=tcanvas.toDataURL();}});
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/1.0.2/Chart.min.js"></script><h4>ChartJS 折线图</h4><div style="width:30%"><div><canvas id="canvas" height="450" width="600"></canvas>
<h4>完全不透明的图表作为图像</h4>
I'm working with Chart.js and want to convert a line chart to a PNG. The problem is that the image always downloads with a transparent background, which is not what I need. I tried many options, nothing really worked.
And suggestions?
Here's one way to get a fully-opaque version of your ChartJS:
Wait until the chart is fully animated out and complete. You can do this by adding the onAnimationComplete
property to the chart.
In the onAnimationComplete
function:
- Create an in-memory temporary canvas of equal size as your chart.
- Fill the temp canvas with white
drawImage
the ChartJS canvas over the white-filled temp canvas- Create an image from the temp canvas.
Here's how that might be done:
var ctx = document.getElementById("canvas").getContext("2d");
window.myLine = new Chart(ctx).Line(lineChartData, {
responsive: true,
onAnimationComplete:function(){
var tcanvas=document.createElement('canvas');
var tctx=tcanvas.getContext('2d');
tcanvas.width=ctx.canvas.width;
tcanvas.height=ctx.canvas.height;
tctx.fillStyle='white';
tctx.fillRect(0,0,tcanvas.width,tcanvas.height);
tctx.drawImage(canvas,0,0);
var img=new Image();
img.onload=function(){
document.body.appendChild(img);
}
img.src=tcanvas.toDataURL();
}
});
Here's example code and a Demo:
var randomScalingFactor = function(){ return Math.round(Math.random()*100)};
var randomColorFactor = function(){ return Math.round(Math.random()*255)};
var lineChartData = {
labels : ["January","February","March","April","May","June","July"],
datasets : [
{
label: "My First dataset",
fillColor : "rgba(220,220,220,0.2)",
strokeColor : "rgba(220,220,220,1)",
pointColor : "rgba(220,220,220,1)",
pointStrokeColor : "#fff",
pointHighlightFill : "#fff",
pointHighlightStroke : "rgba(220,220,220,1)",
data : [randomScalingFactor(),randomScalingFactor(),randomScalingFactor(),randomScalingFactor(),randomScalingFactor(),randomScalingFactor(),randomScalingFactor()]
},
{
label: "My Second dataset",
fillColor : "rgba(151,187,205,0.2)",
strokeColor : "rgba(151,187,205,1)",
pointColor : "rgba(151,187,205,1)",
pointStrokeColor : "#fff",
pointHighlightFill : "#fff",
pointHighlightStroke : "rgba(151,187,205,1)",
data : [randomScalingFactor(),randomScalingFactor(),randomScalingFactor(),randomScalingFactor(),randomScalingFactor(),randomScalingFactor(),randomScalingFactor()]
}
]
}
var ctx = document.getElementById("canvas").getContext("2d");
window.myLine = new Chart(ctx).Line(lineChartData, {
responsive: true,
onAnimationComplete:function(){
var tcanvas=document.createElement('canvas');
var tctx=tcanvas.getContext('2d');
tcanvas.width=ctx.canvas.width;
tcanvas.height=ctx.canvas.height;
tctx.fillStyle='white';
tctx.fillRect(0,0,tcanvas.width,tcanvas.height);
tctx.drawImage(canvas,0,0);
var img=new Image();
img.onload=function(){
document.body.appendChild(img);
}
img.src=tcanvas.toDataURL();
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/1.0.2/Chart.min.js"></script>
<h4>ChartJS line chart</h4>
<div style="width:30%">
<div>
<canvas id="canvas" height="450" width="600"></canvas>
</div>
</div>
<h4>Fully opaque chart as image</h4>
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