URI::GoogleChart - Generate Google Chart URIs


 use URI::GoogleChart;
 my $chart = URI::GoogleChart->new("lines", 300, 100,
     data => [45, 80, 55, 68],
     range_show => "left",
     range_round => 1,

 # save chart to a file
 use LWP::Simple qw(getstore);
 getstore($chart, "chart.png");

 # or embed chart in an HTML file
 use HTML::Entities;
 my $enc_chart = encode_entities($chart);

 open(my $fh, ">", "chart.html") || die;
 print $fh qq(
     <h1>My Chart</h1>
     <p><img src="$enc_chart"></p>
 close($fh) || die;


This module provide a constructor method for Google Chart URLs. When dereferenced Google will serve back PNG images of charts based on the provided parameters.

The Google Chart service is described at and these pages also define the Web API in terms of the parameters these URLs take. This module make it easier to generate URLs that conform to this API as it automatically takes care of data encoding and scaling, as well as hiding most of the cryptic parameter names that the API uses in order to generate shorter URLs.

The following constructor method is provided:

$uri = URI::GoogleChart->new( $type, $width, $height, %opt )

The constructor method's first 3 arguments are mandatory and they define the type of chart to generate and the dimension of the image in pixels. Additional arguments are provided as key/value pairs. The return value is an HTTP URI object, which can also be treated as a string.

The $type argument can either be one of the type code documented at the Google Charts page or one of the following more readable aliases:






The additional arguments in the form of key/value pairs can either be one of the chXXX parameters documented on the Google Chart pages or one of the following:

data => [{ v => [$v1, $v2,...], %opt }, ...]
data => [[$v1, $v2,...], [$v1, $v2,...], ...]
data => [$v1, $v2,...]
data => $v1

The data to be charted is provided as an array of data series. In the most general form each series is defined by a hash with the "v" element being an array of data points (numbers) in the series. Missing data points should be provided as undef. Other hash elements can be provided to define various properties of the series. These are described below.

As a short hand when you don't need to define other properties besides the data points you can provide an array of numbers instead of the series hash.

As a short hand when you only have a single data series, you can provide a single array of numbers, and finally if you only have a single number you can provide it without wrapping it in an array.

Data series belong to ranges. A range is defined by a minimum and a maximum value. Data points are scaled so that they are plotted relative to the range they belong to. For example if the range is (5 .. 10) then a data point value of 7.5 is plotted in the middle of the chart area. Ranges are automatically calculated based on the data provided, but you can also force certain minimum and maximum values to apply.

The following data series properties can be provided in addition to "v" described above:

The "range" property can be used to group data series together that belong to the same range. The value of the "range" property is a range name. Data series without a "range" property belong to the default range.

min => $num
max => $num

Defines the default minimum and maximum value for the default range. If not provided the minimum and maximum is calculated from the data points belonging to this range.

The specified minimum or maximum are ignored if some of data values provided are outside this range.

Chart types that plot relative values (like bar charts or venn diagrams) should use 0 as the minimum, as this make the relative size of the data points stay the same after scaling. Because of this the default default minimum for these charts is 0, so you don't actually need to specify it.

range_round => $bool

Extend the default range so that the min/max values are nice multiples of 1, 5, 10, 50, 100,... and such numbers. This gives the chart more "air" and look better if you display the range of values with "range_show".

range_show => "left"
range_show => "right"
range_show => "top"
range_show => "bottom"

Makes the given axis show the range of values charted for the default range.

range => { $name => \%opt, ...},

Define parameters for named data series ranges. The range named "" is the default range.

The option values that can be set are "min", "max", "round", "show". See the description of the corresponding entry for the default range above.

encoding => "t"
encoding => "s"
encoding => "e"

Select what kind of data encoding you want to be used. They differ in the resolution they provide and in their readability and verbosity. Resolution matters if you generate big charts. Verbosity matters as some web client might refuse to dereference URLs that are too long.

The "t" (or "text") encoding is the most readable and verbose. It might consume up to 5 bytes per data point. It provide a resolution of 1/1000.

The "s" (or "simple") encoding is the most compact; only consuming 1 byte per data point. It provide a resolution of 1/62.

The "e" (or "extended") encoding provides the most resolution and it consumes 2 bytes per data point. It provide a resolution of 1/4096.

The default encoding is automatically selected based on the resolution of the chart and the number of data points provided.

color => $color
color => [$color1, $color2, ...]

Sets the colors to use for charting the data series. The canonical form for $color is hexstrings either of "RRGGBB" or "RRGGBBAA" form. When you use this interface you might also use "RGB" form as well as some comon names like "red", "blue", "green", "white", "black",... which are expanded to the canonical form in the URL.

The built in colors are the 16 colors of the HTML specification (see If you want to use additional color names you can assign your mapping to the %URI::GoogleChart::COLOR_ALIAS hash before start creating charts. Example:

    local $URI::GoogleChart::COLOR_ALIAS{"gold"} = "FFD700";
background => $color

Sets the color for the chart background. See description for color above for how to specify color values. The color value "transparent" gives you a fully transparent background.

title => $str
title => [ $str, $color, $fontsize ]

Sets the title for the chart; optionally changing the color and fontsize used for the title.

label = $str
label = [ $str, $str,... ]

Labels the data (or data series) of the chart.

rotate => $degrees

Rotate the orientation of a pie chart (clockwise).

The first slice starts at the right side of the pie (at 3 o'clock). If you rotate the pie 90 degrees the first slice starts at the bottom. If you rotate -90 degrees (or 270) the first slices starts at the top of the pie.

margin => $num
margin => [ $left, $right, $top, $bottom ]

Sets the chart margins in pixels. If a single number is provided then all the margins are set to this number of pixels.




Copyright 2009 Gisle Aas.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.