xAxis Image Disappears in Highcharts After First Refresh - highcharts

Question

I have a page with a variety of select menus. The select options are used in an ajax call to build a Highcharts bar graph. Every time a filter changes, the graph gets recreated. I did this instead of updating the series data, because in the past I have noticed that destroying and recreating was more efficient than updating.
I want images to show on the x-axis, so I used a nice little trick of creating two x axes, used formatter to return an image on the first axis, and linked the second axis to the first. This works on first refresh. However, every time the chart gets recreated thereafter, the image disappears. I checked my console and I don't see any errors.
And idea of what's going on here?
/**
* Whenselection changes
*/
$(document).on('change', '.filter', function(){
getChartData($params)
})
});
/**
* API call to get data that will populate charts.
* #param {obj} params
*/
function getChartData(params)
{
//Get chart data
$.ajax({
url: apiURL + '/chartdata/',
data: params,
dataType: 'json',
cache: false,
success: function(data) {
initChart(data[0]);
}
});
function initChart(chartData)
{
var chart = Highcharts.chart('container', {
chart: {
type: 'bar',
backgroundColor: 'transparent', //#E8EAF6',
height: '23%',
marginLeft: 35
},
title: {
text: null
},
xAxis: {
categories: [category1, category2],
lineColor: 'transparent',
min: 0,
tickColor: 'transparent',
title: {
text: null
},
labels: {
x: -35,
useHTML: true,
overflow: 'allow',
formatter: function () {
if(this.isFirst == true)
return '<img src="../assets/img/nat-jr-grad-gold.png"><br/>';
else
return '<img src="../assets/img/nat-jr-grad-purple.png"><br/>';
}
}
},
yAxis: {
min: 0,
title: {
useHTML: true,
text: null
},
labels: {
enabled: false
},
lineWidth: 0,
minorGridLineWidth: 0,
gridLineWidth: 0,
lineColor: 'transparent',
gridLineColor: 'transparent',
},
legend: {
enabled: false
},
series: [{
name: category1,
data: [{name: category1, y:Math.round(chartData.p_grad_nongap * 100), {y: null}],
}, {
name: category2,
data: [null, {name: category2, y: Math.round(chartData.p_grad_gap * 100)}]
}]
});
}

Answer 1

I reproduced your problem on a simplified example: http://jsfiddle.net/BlackLabel/sm2r684n/
For the first time, the image is loaded asynchronously and the chart does not take it into account when calculating the margins. Every next time the result is different, so you should wait until the picture is loaded:
var img = new Image();
img.onload = function() {
initChart();
}
img.src = "https://www.highcharts.com/samples/graphics/sun.png";
Live demo: http://jsfiddle.net/BlackLabel/m09ok2cg/

Answer 2

I think ppotaczek had the cortrect root cause of the problem; the image is loaded asynchronously and the chart does not take it into account when calculating the margins. His suggestion used setTimeout function to continuously redraw the graph, which is rather inefficient. My work-around for this was to just add the images as avg elements using chart.renderer after the chart was created.
/* Render X-Axis images */
chart.renderer.image('../assets/img/img1.png', 0, 40, 32, 36)
.css({
class: 'icon-img',
zIndex: 10
})
.add();
chart.renderer.image('../assets/img/img2.png', 0, 130, 32, 36)
.css({
class: 'icon-img',
zIndex: 10
})
.add();