我正在使用Chart.js。我试图通过获取基本64字符串将图表转换为图像。教程(http://www.chartjs.org/docs/)在主题上使用了整整一行:
canvas元素还允许将内容保存为基础64 字符串,允许将图表保存为图像。
canvas
元素的方法为toDataURL
,它返回图像的base64字符串。但是,当我这样做时,它渲染的图像只是一个带有图表尺寸的透明矩形,并且它不包括图表内容。
这是一个小提琴:http://jsfiddle.net/KSgV7/
小提琴中的“图像”采用黑色边框设计,因此您可以看到它们应该在哪里,因为它们看起来只是一个很大的透明块。
有没有人成功将Chart.js图表转换为图片?
答案 0 :(得分:26)
图表似乎是异步的,因此您可能需要在动画完成时提供回调,否则画布将为空。
var options = {
bezierCurve : false,
onAnimationComplete: done /// calls function done() {} at end
};
答案 1 :(得分:13)
HTML:
<body>
<canvas id="canvas" height="450" width="600"></canvas>
<img id="url" />
</body>
JS:
function done(){
alert("haha");
var url=myLine.toBase64Image();
document.getElementById("url").src=url;
}
var options = {
bezierCurve : false,
animation: {
onComplete: done
}
};
var myLine = new
Chart(document.getElementById("canvas").getContext("2d"),
{
data:lineChartData,
type:"line",
options:options
}
);
答案 2 :(得分:6)
首先将Chart.js画布转换为base64字符串。
var url_base64 = document.getElementById('myChart').toDataURL('image/png');
将其设置为锚标记的href属性。
link.href = url_base64;
<a id='link' download='filename.png'>Save as Image</a>
答案 3 :(得分:2)
您应该使用Chartjs API函数toBase64Image()
,并在动画完成后调用它。因此:
var pieChart, URI;
var options = {
animation : {
onComplete : function(){
URI = pieChart.toBase64Image();
}
}
};
var content = {
type: 'pie', //whatever, not relevant for this example
data: {
datasets: dataset //whatever, not relevant for this example
},
options: options
};
pieChart = new Chart(pieChart, content);
您可以查看此示例并运行它
var chart = new Chart(ctx, {
type: 'bar',
data: {
labels: ['Standing costs', 'Running costs'], // responsible for how many bars are gonna show on the chart
// create 12 datasets, since we have 12 items
// data[0] = labels[0] (data for first bar - 'Standing costs') | data[1] = labels[1] (data for second bar - 'Running costs')
// put 0, if there is no data for the particular bar
datasets: [{
label: 'Washing and cleaning',
data: [0, 8],
backgroundColor: '#22aa99'
}, {
label: 'Traffic tickets',
data: [0, 2],
backgroundColor: '#994499'
}, {
label: 'Tolls',
data: [0, 1],
backgroundColor: '#316395'
}, {
label: 'Parking',
data: [5, 2],
backgroundColor: '#b82e2e'
}, {
label: 'Car tax',
data: [0, 1],
backgroundColor: '#66aa00'
}, {
label: 'Repairs and improvements',
data: [0, 2],
backgroundColor: '#dd4477'
}, {
label: 'Maintenance',
data: [6, 1],
backgroundColor: '#0099c6'
}, {
label: 'Inspection',
data: [0, 2],
backgroundColor: '#990099'
}, {
label: 'Loan interest',
data: [0, 3],
backgroundColor: '#109618'
}, {
label: 'Depreciation of the vehicle',
data: [0, 2],
backgroundColor: '#109618'
}, {
label: 'Fuel',
data: [0, 1],
backgroundColor: '#dc3912'
}, {
label: 'Insurance and Breakdown cover',
data: [4, 0],
backgroundColor: '#3366cc'
}]
},
options: {
responsive: false,
legend: {
position: 'right' // place legend on the right side of chart
},
scales: {
xAxes: [{
stacked: true // this should be set to make the bars stacked
}],
yAxes: [{
stacked: true // this also..
}]
},
animation : {
onComplete : done
}
}
});
function done(){
alert(chart.toBase64Image());
}
&#13;
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.6.0/Chart.min.js"></script>
<canvas id="ctx" width="700"></canvas>
&#13;
答案 4 :(得分:0)
您可以使用afterRender
访问plugins
。{/ p>
而且here都是可用的插件API。
在html文件中:
<html>
<canvas id="myChart"></canvas>
<div id="imgWrap"></div>
</html>
在js文件中:
var chart = new Chart(ctx, {
...,
plugins: [{
afterRender: function () {
// Do anything you want
renderIntoImage()
},
}],
...,
});
const renderIntoImage = () => {
const canvas = document.getElementById('myChart')
const imgWrap = document.getElementById('imgWrap')
var img = new Image();
img.src = canvas.toDataURL()
imgWrap.appendChild(img)
canvas.style.display = 'none'
}
答案 5 :(得分:-1)
您还可以使用toBase64Image()方法设置动画:false
var options = {
bezierCurve : false,
animation: false
};
答案 6 :(得分:-1)
@EH_warch 您需要使用Complete回调来生成base64:
onAnimationComplete: function(){
console.log(this.toBase64Image())
}
如果看到白色图像,则表示在完成渲染之前调用了toBase64Image。
答案 7 :(得分:-2)
我使用Chartjs.js库在此代码中解决了此问题
HTML代码:
<img id="ChartImage" style="margin: 0 auto;" />
<canvas id="myChart" style="margin: 0 auto;" ></canvas>
JavaScript图表选项:
options: {
legend: { position: 'bottom', display: true },
animation: {
onComplete: function(){
var url = barChart.toBase64Image(); //get image as base64
document.getElementById("ChartImage").src = url; //to fill image in html
}
}
},