Efficient method for putting colormaps into color ramp?

Question

I created an addon to use the colormaps from Matplotlib

You can get it here

https://github.com/TheJeran/Blender-Colormaps/

Original Question

Does anyone have an efficient method for importing color maps into a color ramp?

At the moment I have to get the hex codes for each step in a colorramp.

Anyone know a better idea?

Answer 1

Run script to add ColorRamp to specify material

Hex version

import bpy, math

material_name = "Material"  # choose your material_name here

color = [
(0xE76254, 1),  # red = 231, green = 98, blue = 84, alpha = 1, allow lower case
(0xEF8A47, 1),
(0xF7AA58, 1),
(0xFFD06F, 1),
(0xFFE6B7, 1),
(0xAADCE0, 1),
(0x72BCD5, 1),
(0x528FAD, 1),
(0x376795, 1),
(0x1E466E, 1),
]

def to_blender_color(c):    # gamma correction
    c = min(max(0, c), 255) / 255
    return c / 12.92 if c < 0.04045 else math.pow((c + 0.055) / 1.055, 2.4)

blend_color = [(
    to_blender_color(c[0] >> 16),
    to_blender_color(c[0] >> 8 & 0xff), 
    to_blender_color(c[0] & 0xff),
    c[1]) for c in color]
color_count = len(color)

for e in blend_color:
    print(e)

mat     = bpy.data.materials[material_name] # choose material name here
tree    = mat.node_tree
nodes   = tree.nodes
node    = nodes.new(type='ShaderNodeValToRGB') # add color ramp node

ramp    = node.color_ramp
el      = ramp.elements

dis     = 1 / (color_count - 1)
x       = dis
for r in range(color_count - 2):
    el.new(x)
    x += dis

for i, e in enumerate(el):
    e.color = blend_color[i]

Dec Version

import bpy, math

material_name = "Material"  # choose your material_name here

color = [
(231, 98, 84, 1),
(247, 170, 88  1),
(..., 1),
]

def to_blender_color(c):    # gamma correction
    c = min(max(0, c), 255) / 255
    return c / 12.92 if c < 0.04045 else math.pow((c + 0.055) / 1.055, 2.4)

blend_color = [(
    to_blender_color(c[0]),
    to_blender_color(c[1]), 
    to_blender_color(c[2]),
    c[3]) for c in color]
color_count = len(color)

for e in blend_color:
    print(e)

mat     = bpy.data.materials[material_name] # choose material name here
tree    = mat.node_tree
nodes   = tree.nodes
node    = nodes.new(type='ShaderNodeValToRGB') # add color ramp node

ramp    = node.color_ramp
el      = ramp.elements

dis     = 1 / (color_count - 1)
x       = dis
for r in range(color_count - 2):
    el.new(x)
    x += dis

for i, e in enumerate(el):
    e.color = blend_color[i]

Answer 2

Of course you have the possibility to use an image as color reference.

But if you really want to transfer your color values directly into a ColorRamp without knowing their HEX values, a small Python script will help you.

It simply references an image (previously imported into Blender) by name, determines the color values of the pixels at certain positions and transfers them to a ColorRamp.

All you need for this example is that the color gradient runs horizontally and that you know the number of your colors and enter them into the script.

Furthermore, you have to enter the name of the previously imported image, as well as the name of your material.

In detail the following happens here:

1. First the dimensions of the image are determined.

2. Then a reference to the specified material is created and a new node of the type ColorRamp is created there.

3. In the loop, using the number of color values you specified, the pixel for reading the color is determined.

   These color values are then transferred directly to the new positions of the ColorRamp created at the same time.

import bpy
from bpy import data as D

imageFile = "colorramp.png"
materialName = "Material"
colorCount = 10

# Get the reference to the specified image
img = D.images[imageFile]

# Determine height and width of the image
width = img.size[0]
height = img.size[1]

# Get the reference to the specified material
material = bpy.data.materials[materialName]

# Get the node collection of the material
nodes = material.node_tree.nodes

# Create a color ramp node
color_ramp = material.node_tree.nodes.new("ShaderNodeValToRGB")

# Get a reference to the colorRamp node
cr=D.materials[materialName].node_tree.nodes["ColorRamp"].color_ramp

# Set interpolation between color stops to "CONSTANT"
cr.interpolation = "CONSTANT"

# Convert sRGB to linear RGB
def sRGB2linear(s):
    if s <= 0.0404482362771082:
        lin = s / 12.92
    else:
        lin = ((s + 0.055) / 1.055) ** 2.4
    return lin

# Iterate through the colors
for x in range(colorCount):
    # Define the position of the pixel we want to read out
    target = [round(x * (width / colorCount) + width / colorCount/2), round(height / 2)]
    # Determine the index of the pixel to be read out (#RGBA)
    index = (target[1] * width + target[0]) * 4
    if (x > 0 and x < colorCount -1):
        # Add a new position to the ColorRamp
        cr.elements.new(position = 1 / (colorCount - 1) * x)
    
    # Read the color at the given index and set the color in the ColorRamp
    cr.elements[x].color=(
        sRGB2linear(img.pixels[index]), # R
        sRGB2linear(img.pixels[index + 1]), #G
        sRGB2linear(img.pixels[index + 2]), #B
        1, #A
    )

UPDATE: Added conversion from sRGB to linear.

Answer 3

I created an addon to use the colormaps from Matplotlib

You can get it here

https://github.com/TheJeran/Blender-Colormaps/