django-chart-tools 1.0
A thin wrapper around Google Chart API that tries not to invent a new language for describing charts.
License: MIT license

==================
django-chart-tools
==================

django-chart-tools is a simple app for creating charts in django templates
using Google Chart API. It doesn't try to invent another language for defining
charts unlike other Google Chart API wrappers. It instead make it easy to
leverage the power of existing user-friendly chart-building tools like
http://dexautomation.com/googlechartgenerator.php

.. warning::

    Please note that Image Chart API (that django-chart-tools is using)
    is deprecated by Google.

Installation
============

::

    $ pip install django-chart-tools

or ::

    $ easy_install django-chart-tools

or grab the latest and the greatest version from bitbucket
(https://bitbucket.org/kmike/django-chart-tools)

Then add 'chart_tools' to your INSTALLED_APPS.

Usage
=====

1. Generate a chart you like using
   http://dexautomation.com/googlechartgenerator.php or by following API docs
   https://developers.google.com/chart/image/docs/gallery/chart_gall.

2. Copy&paste output to your template and wrap it with
   {% chart %} ... {% endchart %} tags::

        {% load chart_tags %}
        {% chart %}
            http://chart.apis.google.com/chart
               ?chxr=0,0,160
               &chxt=y
               &chbh=a
               &chs=440x220
               &cht=bvs
               &chco=4D89F9
               &chds=0,160
               &chd=t:10,50,60,80,40,60,30
               &chtt=Horizontal+bar+chart
        {% endchart %}

   You'll get the <img/> tag with generated chart in you template after rendering.

3. chart tag also allows cleaned-up version of the example above::

       {% load chart_tags %}
       {% chart %}
            chxr=0,0,160
            chxt=y
            chbh=a
            chs=440x220
            cht=bvs
            chco=4D89F9
            chds=0,160
            chd=t:10,50,60,80,40,60,30
            chtt=Horizontal+bar+chart
       {% endchart %}

4. Replace test data with your real data. For example, we want to provide
   real values. Change the test data in Image Chart Editor. The
   parameter we change will be highlited. It is 'chd' in our case. So now
   we replace 'chd' data with real data that comes from view::

      {% load chart_tags %}
      {% chart %}
           chxr=0,0,160
           chxt=y
           chbh=a
           chs=440x220
           cht=bvs
           chco=4D89F9
           chds=0,160
           chd=t:{{ values|join:',' }}
           chtt=Horizontal+bar+chart
      {% endchart %}

That's all.

There is also up-to-date API reference from Google:
https://developers.google.com/chart/image/docs/chart_params

What is {% chart %} tag for
===========================

I found plain copy-pasted <img> html tag with some {{ variables }}
unmaintainable and unreadable so the {% chart %} was introduced.

1. It removes all whitespaces;
2. builds chart url from parameter list;
3. generates the <img> tag with proper 'src', 'width' and 'height' attributes

so generated charts can be nicely formatted and it is possible to maintain
them later.


Reusable chart tags
===================

Once you created a chart you like you'll possibly want to use it multiple
times. The preferred way is to write inclusion template tag around your
template::

    from django import template
    register = template.Library()

    @register.inclusion_tag('chart_tools/bar_chart.html')
    def bar_chart(values, captions, size='580x100', max_value=None):
        max_value = max_value or max(values)
        return {
            'values': values,
            'captions': captions,
            'size': size,
            'max_value': max_value,
        }

This example bar_chart tag is included in django-chart-tools.