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Gradient or image in background (chartjs) #1846

Open Thomas opened this topic on on Jan 13 - 3 comments

Thomas commented on Jan 13

Is it possible to add a gradient to the background of a chart?

If not, could I add an image to the background of the data area? With css I can only add it to the whole background but I want it to show only in the data area (without the scale).

David Winterburn commented on Jan 14

Which type of chart (bar, line, area, etc) are you talking about? Thanks!

Thomas commented on Jan 14

Bubble chart (chartjs).

David Winterburn commented on Jan 15

At the moment it's not easy to set an option for Chartjs' bubble chart to have a gradient background. Please try the following method:

1 . Create a file call MyBubbleChart.php in koolreport/chartjs directory with the following content:


namespace koolreport\chartjs;
use \koolreport\core\Utility;

class MyBubbleChart extends BubbleChart
    protected function processData()
        $datasets = array();
        foreach($this->series as $i=>$series)
            $columnKeys = array();
            $dataset = array(
                "label"=>"Series $i",
                "backgroundColor"=>"function getGradient() {
                    var ctx = document.getElementById('{$this->name}').getContext('2d');
                    var gradient = ctx.createLinearGradient(0, 0, 0, 400);
                    gradient.addColorStop(0, 'rgba(250,174,50,1)');  //modify these lines for your preferred gradient
                    gradient.addColorStop(1, 'rgba(250,174,50,0)');
                    return gradient;
            foreach($series as $item)
                    $dataset = array_merge($dataset,$item);
            $dataset["data"] = array();
            while($row = $this->dataStore->pop())
        return array(


Then in your report view use \koolreport\chartjs\MyBubbleChart widget instead of \koolreport\chartjs\BubbleChart.

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