ChartDirector 6.0 (Python Edition)

Contour Color Scale


      

This example demonstrates using various coloring for the ContourLayer.

The ChartDirector supports two ways to configure the colors for a contour.

This example includes 4 charts to demonstrate both of the above methods.

Source Code Listing

[Standalone Version] pythondemo\contourcolor.py
#!/usr/bin/python
from pychartdir import *

def createChart(chartIndex) :

    # The x and y coordinates of the grid
    dataX = [-4, -3, -2, -1, 0, 1, 2, 3, 4]
    dataY = [-4, -3, -2, -1, 0, 1, 2, 3, 4]

    # Use random numbers for the z values on the XY grid
    r = RanSeries(99)
    dataZ = r.get2DSeries(len(dataX), len(dataY), -0.9, 0.9)

    # Create a XYChart object of size 420 x 360 pixels
    c = XYChart(420, 360)

    # Set the plotarea at (30, 25) and of size 300 x 300 pixels. Use semi-transparent grey
    # (0xdd000000) horizontal and vertical grid lines
    c.setPlotArea(30, 25, 300, 300, -1, -1, -1, 0xdd000000, -1)

    # Set the x-axis and y-axis scale
    c.xAxis().setLinearScale(-4, 4, 1)
    c.yAxis().setLinearScale(-4, 4, 1)

    # Add a contour layer using the given data
    layer = c.addContourLayer(dataX, dataY, dataZ)

    # Move the grid lines in front of the contour layer
    c.getPlotArea().moveGridBefore(layer)

    # Add a color axis (the legend) in which the top left corner is anchored at (350, 25). Set the
    # length to 400 300 and the labels on the right side.
    cAxis = layer.setColorAxis(350, 25, TopLeft, 300, Right)

    if chartIndex == 1 :
        # Speicify a color gradient as a list of colors, and use it in the color axis.
        colorGradient = [0x0044cc, 0xffffff, 0x00aa00]
        cAxis.setColorGradient(0, colorGradient)
    elif chartIndex == 2 :
        # Specify the color scale to use in the color axis
        colorScale = [-1.0, 0x1a9850, -0.75, 0x66bd63, -0.5, 0xa6d96a, -0.25, 0xd9ef8b, 0, 0xfee08b,
            0.25, 0xfdae61, 0.5, 0xf46d43, 0.75, 0xd73027, 1]
        cAxis.setColorScale(colorScale)
    elif chartIndex == 3 :
        # Specify the color scale to use in the color axis. Also specify an underflow color 0x66ccff
        # (blue) for regions that fall below the lower axis limit.
        colorScale = [0, 0xffff99, 0.2, 0x80cdc1, 0.4, 0x35978f, 0.6, 0x01665e, 0.8, 0x003c30, 1]
        cAxis.setColorScale(colorScale, 0x66ccff)

    # Output the chart
    c.makeChart("contourcolor%s.png" % chartIndex)


createChart(0)
createChart(1)
createChart(2)
createChart(3)

[CGI Version] pythondemo_cgi\contourcolor.py
#!/usr/bin/python
from pychartdir import *
import cgi, sys

# Get HTTP query parameters
query = cgi.FieldStorage()

# This script can draw different charts depending on the chartIndex
chartIndex = int(query["img"].value)

# The x and y coordinates of the grid
dataX = [-4, -3, -2, -1, 0, 1, 2, 3, 4]
dataY = [-4, -3, -2, -1, 0, 1, 2, 3, 4]

# Use random numbers for the z values on the XY grid
r = RanSeries(99)
dataZ = r.get2DSeries(len(dataX), len(dataY), -0.9, 0.9)

# Create a XYChart object of size 420 x 360 pixels
c = XYChart(420, 360)

# Set the plotarea at (30, 25) and of size 300 x 300 pixels. Use semi-transparent grey (0xdd000000)
# horizontal and vertical grid lines
c.setPlotArea(30, 25, 300, 300, -1, -1, -1, 0xdd000000, -1)

# Set the x-axis and y-axis scale
c.xAxis().setLinearScale(-4, 4, 1)
c.yAxis().setLinearScale(-4, 4, 1)

# Add a contour layer using the given data
layer = c.addContourLayer(dataX, dataY, dataZ)

# Move the grid lines in front of the contour layer
c.getPlotArea().moveGridBefore(layer)

# Add a color axis (the legend) in which the top left corner is anchored at (350, 25). Set the
# length to 400 300 and the labels on the right side.
cAxis = layer.setColorAxis(350, 25, TopLeft, 300, Right)

if chartIndex == 1 :
    # Speicify a color gradient as a list of colors, and use it in the color axis.
    colorGradient = [0x0044cc, 0xffffff, 0x00aa00]
    cAxis.setColorGradient(0, colorGradient)
elif chartIndex == 2 :
    # Specify the color scale to use in the color axis
    colorScale = [-1.0, 0x1a9850, -0.75, 0x66bd63, -0.5, 0xa6d96a, -0.25, 0xd9ef8b, 0, 0xfee08b,
        0.25, 0xfdae61, 0.5, 0xf46d43, 0.75, 0xd73027, 1]
    cAxis.setColorScale(colorScale)
elif chartIndex == 3 :
    # Specify the color scale to use in the color axis. Also specify an underflow color 0x66ccff
    # (blue) for regions that fall below the lower axis limit.
    colorScale = [0, 0xffff99, 0.2, 0x80cdc1, 0.4, 0x35978f, 0.6, 0x01665e, 0.8, 0x003c30, 1]
    cAxis.setColorScale(colorScale, 0x66ccff)

# Output the chart
print("Content-type: image/png\n")
binaryPrint(c.makeChart2(PNG))