How to Download a Google Chart as a bitmap


Some Google Charts can be downloaded as a bitmap image and embedded in a PDF or saved to disk. A button added to a UX Component can be used to download a chart created using the Google Chart API.

For some charts, the chart object created from the Google visualizations API has a method called getImageURI that can be called to get the base64 encoded data for the chart. This data can then be integrated into a report or saved as an image.

For example, the following function creates a combo chart and displays it in the HTML element with an ID of 'visualization'.

function barAndLineChart() {
    // Some raw data (not necessarily accurate)
    var data = google.visualization.arrayToDataTable([
        ['Month', 'Bolivia', 'Ecuador', 'Madagascar', 'Papua New Guinea', 'Rwanda', 'Average'],
        ['2004/05',  165,      938,         522,             998,           450,      614.6],
        ['2005/06',  135,      1120,        599,             1268,          288,      682],
        ['2006/07',  157,      1167,        587,             807,           397,      623],
        ['2007/08',  139,      1110,        615,             968,           215,      609.4],
        ['2008/09',  136,      691,         629,             1026,          366,      569.6]

    var options = {
        title : 'Monthly Coffee Production by Country',
        vAxis: {title: "Cups"},
        hAxis: {title: "Month"},
        seriesType: "bars",
        series: {5: {type: "line"}}

    var chart = new google.visualization.ComboChart($('visualization'));
    chart.draw(data, options);

    {dialog.object}._chart = chart; 

The chart object is stored in the {dialog.object}._chart variable. This makes it possible to reference the chart in another function that is called when a button is clicked:

function downloadChart() { 
    var chart =  {dialog.object}._chart;
    if(typeof chart == 'undefined') { 
        alert('You must click a button to select a chart type before you can download a chart.');
        return false;
    if(typeof chart.getImageURI == 'function' ) { 
        var base64data = chart.getImageURI();
        var _d = A5.ajax.buildURLParam('_base64data',base64data)
        //make an ajax callback with the data
    } else { 
        alert('This type of chart does not support downloading');

The downloadChart function gets the base64 encoded image of the chart from the chart object if the chart object supports the getImageURI method. The base64 encoded image is then sent to the server to be converted into a bitmap by the printChart ajax callback:

function printChart as c (e as p)

    'this function handles the Ajax callback to download the chart as an image.
    dim data as c 
    'get the base64 encoded image
    data = e._base64data 
    'the string should start with a prefix that looks like this: data:image/png;base64,
    dim b as b 
    dim type as c 
    dim prefix as c 
    if atc("data:image",data) = 0 then 
        printChart = "alert('data is not valid. expecting a base64 encoded string');"
        exit function 
    end if 
    prefix = word(data,1,",")
    data = word(data,2,",",9999999999)
    dim type as c 
    type = word(prefix,1,";")
    type = word(type,2,"/")
    b = base64decode(data)
    dim fn as c 
    fn = a5_create_tempfile("." + type)
    dim js as c 
    if e.tmpl.embeddedMode = .t. then 'working preview
        dim xbencoded as c 
        xbencoded = "sys_open(\"" + fn + "\")"
        xbencoded = stritran(xbencoded,chr(92),"||!||")
        js  = "genericXbasicUIFromWorkingPreview('"+xbencoded+"');"
    else 'live mode
        dim key as c 
        key = file.filename_parse(fn,"ne")
        session.saveFileToSessionFile(fn,"A5SessionFile__" +key)
        fn = "A5SessionFile__" +key
        delete pu
        dim pu as p
        pu.fileToDownload = fn 
        pu.csfilename = "chart." + type
        dim url as c 
        url = a5_property_to_attribute(pu,.t.)
        url = js_escape(url)
        url = "__A5FileDownload.a5w?" + url
        js = js + "var url = '" + url + "';" + crlf()
        js = js + "var ifr = '"+e.tmpl.alias+".__IFRAME1';"
        js = js + "$(ifr).src = url;"
    end if 

    printChart = js 

end function

For a full description of how to download a Google chart object as an image, watch the video below:

Not all Google chart types support this feature.

Downloading a Google Chart as a Bitmap

Download Component


See Also