const char *getHTMLImageMap(const char *url, const char *queryFormat = 0, const char *extraAttr = 0, int offsetX = 0, int offsetY = 0);

Generates an HTML image map for the chart.

This method generates an image map to represent all data points on the chart. It does not include legend box, title box or custom text box. Please use LegendBox.getHTMLImageMap or Box.getImageCoor to produce image maps for these objects.

This method should be called only after creating the chart image (eg. using BaseChart.makeChart, BaseChart.makeChart2 or BaseChart.makeChart3). The image map cannot be determined without creating the chart image first.

This method accepts a URL as its argument. When generating an image map, it appends query parameters to the URL to indicate which data point the user has clicked.

The following is an example image map generated for a bar chart with 3 bars.


The image map consists of multiple <area> tags, one for each bar in the chart. In the "href" attributes, query parameters are appended to the URL to provide information on the bar clicked.

The image map produces by ChartDirector does not include the <map> and </map> tag. This is intentional so that you can add additional custom <area> tags to the image map, or append multiple image maps together.

The type of query parameters to append to the URL depends on the chart type and layer type. The default query parameters are as follows.

Chart/Layer Type	Default Query Format
Pie chart	sector={sector}&label={label}&value={value}&percent={percent}
Bar, Line, Spline, Step Line, Area and Scatter layers	x={x}&xLabel={xLabel}&dataSet={dataSet}&dataSetName={dataSetName}&value={value}
Percentage Bar and Percentage Area layers	x={x}&xLabel={xLabel}&dataSet={dataSet}&dataSetName={dataSetName}&value={value}&percent={percent}
HLOC and CandleStick layers	x={x}&xLabel={xLabel}&high={high}&low={low}&open={open}&close={close}
Box-Whisker layer	x={x}&xLabel={xLabel}&top={top}&bottom={bottom}&max={max}&min={min}&med={med}
Trend layer	dataSetName={dataSetName}
Vector layer and Polar Vector layer	x={x}&xLabel={xLabel}&dataSetName={dataSetName}&value={value}&dir={dir}&len={len}
Polar Line, Area, Spline Line and Spline Area layers	"x={x}&label={label}&name={name}&value={value}"

The texts in curly brackets (e.g. {sector}, {dataSet}, etc.) will be replaced by the actual values when generating the image map. For example, {sector} will be replaced by the sector number of the sector.

ChartDirector allows developers to modify the query parameters by using the queryFormat argument. For example, if "x={x}&v={value}" is used as the queryFormat for a XYChart, only the x position and the value of the data point will be included in query parameters.

Please refer to Parameter Substitution and Formatting on all available parameters and their meanings.

In addition to customizing the query parameters, ChartDirector supports additional HTML attributes in the <area> tags by using the extraAttr argument.

For example, the following extraAttr will add an "title" HTML attribute to every <area> tag. The attribute which will contain the x-axis label and the value of the data point. The "title" attribute will be displayed as "tool tip" when the mouse moves over the image map.


Another common usage of the extraAttr argument is to add "onmouseover" and "onmouseout" HTML attributes to handle user interaction using Javascript on the browser.

Argument	Default	Description
url	(Mandatory)	The URL to be used in the "href" attribute of the image map. Parameter Substitution and Formatting is supported. Use an empty string if no href attribute is needed.
queryFormat	""	A text string representing the template of the query parameters to be appended to the URL. Parameter Substitution and Formatting is supported. The special keyword "{default}" represents the default query parameters. This is useful for specifying appending to the default. Note that an empty string means to use the default query query parameters. To specify no query parameter, use a space character.
extraAttr	""	A text string to specify additional attributes to add to the <area> tag. Parameter Substitution and Formatting is supported.
offsetX	0	An offset to be added to all x coordinates in the image map. This is useful if the current image will be shifted and inserted into another image. In this case, the image map will need to be shifted by the same offset.
offsetY	0	An offset to be added to all y coordinates in the image map. See offsetX above for description.

A text string containing the image map generated.