How to add image/icon below y-axis in column highcharts - highcharts

Question

I have integrated a column highchart in my application having primary and secondary y-axis(dual-axis). Now I need to add an image/icon below both y-axes for reference of the axis. I have implemented below code:
Highcharts.chart('container', {
chart: {
type: 'column'
},
title: {
text: null
},
subtitle: {
text: null
},
xAxis: [{
categories: ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'],
crosshair: true
}],
yAxis: [{ // Primary yAxis
labels: {
format: '{value}°C',
style: {
color: Highcharts.getOptions().colors[1]
}
},
title: {
text: 'Temperature',
style: {
color: Highcharts.getOptions().colors[1]
}
}
}, { // Secondary yAxis
title: {
text: 'Rainfall',
style: {
color: Highcharts.getOptions().colors[0]
}
},
labels: {
format: '{value} mm',
style: {
color: Highcharts.getOptions().colors[0]
}
},
opposite: true
}],
tooltip: {
shared: true
},
legend: {
layout: 'horizontal',
align: 'center',
verticalAlign: 'bottom'
},
series: [{
name: 'Rainfall',
type: 'column',
yAxis: 1,
data: [49.9, 71.5, 106.4, 129.2, 144.0, 176.0, 135.6, 148.5, 216.4, 194.1, 95.6, 54.4],
tooltip: {
valueSuffix: ' mm'
}
}, {
name: 'Temperature',
type: 'spline',
data: [7.0, 6.9, 9.5, 14.5, 18.2, 21.5, 25.2, 26.5, 23.3, 18.3, 13.9, 9.6],
tooltip: {
valueSuffix: '°C'
}
}]
});
<script src="https://code.highcharts.com/highcharts.js"></script>
<figure class="highcharts-figure">
<div id="container"></div>
</figure>
Now I need to add an icon below both y-axes for reference of the axis. Any help would be definitely appreciated!

Answer 1

You can add the image as an axis title located below the plot area:
yAxis: [{
title: {
text: '<img src="https://www.highcharts.com/samples/graphics/sun.png" />',
align: 'low',
useHTML: true,
rotation: 0,
reserveSpace: false,
y: 40
}
}, {...}]
Live demo: http://jsfiddle.net/BlackLabel/mzquL6je/
API Reference: https://api.highcharts.com/highcharts/yAxis.title