How Do I...?

Note

This section is currently under active development.

Basics

How do I...

  • render data to an image file?
def save_plot(plot, filename, width, height):
    plot.outer_bounds = [width, height]
    plot.do_layout(force=True)
    gc = PlotGraphicsContext((width, height), dpi=72)
    gc.render_component(plot)
    gc.save(filename)
  • integrate a Chaco plot into my WX app?
import wx
from numpy import arange
from scipy.special import jn
from chaco.api import HPlotContainer, create_line_plot
from enable.api import Window

class PlotFrame(wx.Frame):
    def __init__(self, *args, **kw):
        kw["size"] = (850, 550)
        wx.Frame.__init__( *(self,) + args, **kw )
        self.plot_window = Window(self, component=self._create_plot())
        sizer = wx.BoxSizer(wx.HORIZONTAL)
        sizer.Add(self.plot_window.control, 1, wx.EXPAND)
        self.SetSizer(sizer)
        self.SetAutoLayout(True)
        self.Show(True)
        return

    def _create_plot(self):
        x = arange(-5.0, 15.0, 20.0/100)
        y = jn(0, x)
        plot = create_line_plot((x,y), bgcolor="white",
                                    add_grid=True, add_axis=True)
        container = HPlotContainer(spacing=20, padding=50, bgcolor="lightgray")
        container.add(plot)
        return container

if __name__ == "__main__":
    app = wx.PySimpleApp()
    frame = PlotFrame(None)
    app.MainLoop()

Note that this will require for the ETS_TOOLKIT environment variable to be set to ‘wx’.

  • integrate a Chaco plot into my QT app?
  • integrate a Chaco plot into my Traits UI?
import numpy
from chaco.api import Plot, ArrayPlotData
from enable.component_editor import ComponentEditor
from traits.api import HasTraits, Instance
from traitsui.api import Item, View

class MyPlot(HasTraits):
    plot = Instance(Plot)

    traits_view = View(Item('plot', editor=ComponentEditor()))

    def __init__(self, index, data_series, **kw):
        super(MyPlot, self).__init__(**kw)

        plot_data = ArrayPlotData(index=index)
        plot_data.set_data('data_series', data_series)
        self.plot = Plot(plot_data)
        self.plot.plot(('index', 'data_series'))

index = numpy.array([1,2,3,4,5])
data_series = index**2

my_plot = MyPlot(index, data_series)
my_plot.configure_traits()
  • make an application to render many streams of data?
def plot_several_series(index, series_list):
    plot_data = ArrayPlotData(index=index)
    plot = Plot(plot_data)

    for i, data_series in enumerate(series_list):
        series_name = "series_%d" % i
        plot_data.set_data(series_name, data_series)
        plot.plot(('index', series_name))
  • make a plot the right size?
def resize_plot(plot, width, height):
    plot.outer_bounds = [width, height]
  • copy a plot the the clipboard?
def copy_to_clipboard(plot):
    # WX specific, though QT implementation is similar using
    # QImage and QClipboard
    import wx

    width, height = plot.outer_bounds

    gc = PlotGraphicsContext((width, height), dpi=72)
    gc.render_component(plot_component)

    # Create a bitmap the same size as the plot
    # and copy the plot data to it

    bitmap = wx.BitmapFromBufferRGBA(width+1, height+1,
                                 gc.bmp_array.flatten())
    data = wx.BitmapDataObject()
    data.SetBitmap(bitmap)

    if wx.TheClipboard.Open():
        wx.TheClipboard.SetData(data)
        wx.TheClipboard.Close()
    else:
        wx.MessageBox("Unable to open the clipboard.", "Error")

Layout and Rendering

How do I...

  • put multiple plots in a single window?
  • change the background color?
def make_black_plot(index, data_series):
    plot_data = ArrayPlotData(index=index)
    plot_data.set_data('data_series', data_series)
    plot = Plot(plot_data, bgcolor='black')
    plot.plot(('index', 'data_series'))

def change_bgcolor(plot):
    plot.bgcolor = 'black'
  • turn off borders?
def make_borderless_plot(index, data_series):
    plot_data = ArrayPlotData(index=index)
    plot_data.set_data('data_series', data_series)
    plot = Plot(plot_data, border_visible=False)
    plot.plot(('index', 'data_series'))

def change_to_borderless_plot(plot):
    plot.border_visible = False

Writing Components

How do I...

  • compose multiple renderers?
  • write a custom renderer?
  • write a custom overlay/underlay?
  • write a custom tool?
  • write a new container?

Advanced

How do I...

  • properly change/override draw dispatch?
  • modify event dispatch?
  • customize backbuffering?
  • embed custom/native WX widgets on the plot?

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