Color transfer function values in pvpython

ParaView Support
1

Hi there,

I’m attempting to change the colour of a section within a colour bar without impacting the overall gradient on the points outside the changed section.

The closest I have been to achieving this has been through the GUI:

  • Using the default colour bar, there are 3 data points in the ‘color transfer function values’ table - Image 1.
  • Clicking on the colour bar, I can add more values to the table, each inheriting the RBG value to maintain the natural gradient - Image 2.
  • Then I edit a few of these points and I have a yellow section within the un-affected gradient - Image 3.

Is there a way to obtain the RGB values for certain data points using pvpython?
I’ve not found a way to specify a data point (e.g. 0.3 in the example of my images) and have pvpython return the RBG values that correspond.

img1
img11341×906 172 KB

img2
img21331×895 188 KB

img3
img31356×895 198 KB

Best wishes,
Charlie

2

You can get the lookup table object in Python and access its color points with:

lut = GetColorTransferFunction('vOSI')
print(lut.RGBPoints)

RGBPoints is a list of doubles in the order (value_0, red_0, green_0, blue_0, value_1, red_1, green_1, blue_1, ...) You can set the RGB points with

lut.RGBPoints = [25.32328370098179, 0.231373, 0.298039, 0.752941, 2474.27393603584, 0.865003, 0.865003, 0.865003, 4923.224588370698, 0.705882, 0.0156863, 0.14902]

for data points 25.32328370098179, 2474.27393603584, and 4923.224588370698, for instance.

Hope that helps!

3

Hi Corey,

Thank you for the reply!
It half-way helps for sure.

I loaded up the dataset with the default cool-to-warm colour bar and inspected the ‘vOSI’ property.
print(lut.RBGPoints) outputs 3 points with RGB values - start, middle, and end.

Using the GUI on the Color Map Editor, if I then click to make a new point somewhere within that range ParaView creates those RGB values for me.
Is there a function I can call to access those RGB values too?
That way I could write something like this in my script:

# Get the default colour transfer points
lut = GetColorTransferFunction('vOSI')
points = lut.RGBPoints
print(points)
>>> [[0.0, 0.231373, 0.298039, 0.752941,
	 0.25 0.865003, 0.865003, 0.865003,
	 0.50 0.705882, 0.0156863, 0.14902]

# Add several more points with default colour mapping
new_points = [0.0, 0.15, 0.25, 0.37, 0.50]
new_points_RGB = []
for point in new_points:
	new_points_RGB.append(point)
	RGB_values = SomeFunctionToGetDefaultRGB(point)
	new_points_RGB.extend(RGB_values)

print(new_points_RGB)
>>> [[0.0, 0.231373, 0.298039, 0.752941,
	0.15, R, G, B,
	 0.25 0.865003, 0.865003, 0.865003,
	0.37, R, G, B,
	 0.50 0.705882, 0.0156863, 0.14902]

# Applly new points
lut.RGBPoints = new_points_RGB

RGB_values = SomeFunctionToGetDefaultRGB(point)
It’s this line I’m most in need of.
Since it seems something like this happens through the GUI I thought the process should be accessible somehow through Python.
It might need some more input data, like this. But do you know if it’s possible?
RGB_values = SomeFunctionToGetDefaultRGB(point, minimum, maximum, color_preset)

Sorry to be a pain!
Best wishes,
Charlie

4

You can do this:

rgb = [0, 0, 0]
lut.GetClientSideObject().GetColor(100, rgb)
print(rgb)
[0.5647058823529412, 0.6980392156862745, 0.996078431372549]
5

Brilliant, thank you very much!