colors.py

Color manipulation and conversion utilities for Houdini.

This module provides functions for converting between different color formats and managing node color palettes within Houdini. It handles hex colors, RGB floats, and Houdini's native color representations.

Functions:

Name	Description
hex_to_float_rgb	Convert hex color strings to RGB float values
float_rgb_to_hex	Convert RGB float values to hex color strings
color_selected_nodes	Apply colors to selected nodes
validate_palette_file	Validate Houdini color palette files
load_default_palette	Get Houdini's default color palette

color_selected_nodes(node)

Changes the color of the selected nodes with a color palette window.

Opens a color picker dialog and applies the chosen color to selected nodes and an optional target node.

Parameters:

Name	Type	Description	Default
node	Optional[Node]	Additional node to apply color to besides selection. If None, only selected nodes will be colored.	required

Returns:

Type	Description
None	None

Raises:

Type	Description
RuntimeError	If color application fails
ValueError	If node is invalid

Example

change_node_color(hou.node('/obj/geo1')) # Colors geo1 and selection

Source code in utils/colors.py

def color_selected_nodes(node:hou.Node) -> None:
    """Changes the color of the selected nodes with a color palette window.

    Opens a color picker dialog and applies the chosen color to selected nodes
    and an optional target node.

    Args:
        node (Optional[hou.Node]): Additional node to apply color to besides selection.
            If None, only selected nodes will be colored.

    Returns:
        None

    Raises:
        RuntimeError: If color application fails
        ValueError: If node is invalid

    Example:
        >>> change_node_color(hou.node('/obj/geo1'))  # Colors geo1 and selection
    """
    sel = list(hou.selectedNodes())+[node]
    color = (None, sel[0].color())[len(sel) > 0]
    color = hou.ui.selectColor(color)
    if len(sel) > 0 and color != None:
        print(f"The picked color is {color}\nNote: You need to disable the 'Color Correction' flag in the color picker (ramp in the top right) for the colors to be accurate.")
        for sel_node in sel:
            sel_node.setColor(color)

float_rgb_to_hex(red, green, blue)

Convert RGB float values to hex color string.

Parameters:

Name	Type	Description	Default
red	float	Red value (0-1)	required
green	float	Green value (0-1)	required
blue	float	Blue value (0-1)	required

Returns:

Type	Description
str	6-character hex color string without # prefix

Examples:

>>> float_rgb_to_hex(1.0, 0.0, 0.0)
'ff0000'
>>> float_rgb_to_hex(0.0, 1.0, 0.0)
'00ff00'

Source code in utils/colors.py

def float_rgb_to_hex(red: float, green: float, blue: float) -> str:
    """Convert RGB float values to hex color string.

    Args:
        red: Red value (0-1)
        green: Green value (0-1)
        blue: Blue value (0-1)

    Returns:
        6-character hex color string without # prefix

    Examples:
        >>> float_rgb_to_hex(1.0, 0.0, 0.0)
        'ff0000'
        >>> float_rgb_to_hex(0.0, 1.0, 0.0)
        '00ff00'
    """
    red = int(red * 255)
    green = int(green * 255)
    blue = int(blue * 255)
    return f"{red:02x}{green:02x}{blue:02x}"

hex_to_float_rgb(hex_value)

Convert a hex color string to RGB float values.

Parameters:

Name	Type	Description	Default
hex_value	str	Hex color string (e.g. "FF0000" or "#FF0000")	required

Returns:

Type	Description
Tuple[float, float, float]	Tuple of RGB float values from 0-1

Examples:

>>> hex_to_float_rgb("#FF0000")
(1.0, 0.0, 0.0)
>>> hex_to_float_rgb("00FF00")
(0.0, 1.0, 0.0)

Source code in utils/colors.py

def hex_to_float_rgb(hex_value: str) -> Tuple[float, float, float]:
    """Convert a hex color string to RGB float values.

    Args:
        hex_value: Hex color string (e.g. "FF0000" or "#FF0000")

    Returns:
        Tuple of RGB float values from 0-1

    Examples:
        >>> hex_to_float_rgb("#FF0000")
        (1.0, 0.0, 0.0)
        >>> hex_to_float_rgb("00FF00")
        (0.0, 1.0, 0.0)
    """
    hex_value = hex_value.lstrip("#")
    lv = len(hex_value)
    rgb = tuple(int(hex_value[i:i + lv // 3], 16) for i in range(0, lv, lv // 3))
    return tuple(float(i)/256 for i in rgb)

load_default_palette()

Get Houdini's default 36 color palette.

Returns:

Type	Description
List[Tuple[float, float, float]]	List of RGB float tuples representing default colors

Note

The default palette includes white, black, grays, and various hues. Colors are returned as RGB float tuples with values from 0-1.

Source code in utils/colors.py

def load_default_palette() -> List[Tuple[float, float, float]]:
    """Get Houdini's default 36 color palette.

    Returns:
        List of RGB float tuples representing default colors

    Note:
        The default palette includes white, black, grays, and various hues.
        Colors are returned as RGB float tuples with values from 0-1.
    """
    return [
        (1, 1, 1), (0.839, 0.839, 0.839), (0.6, 0.6, 0.6),
        (0.478, 0.478, 0.478), (0.306, 0.306, 0.306), (0, 0, 0),
        (0.384, 0.184, 0.329), (0.576, 0.208, 0.475),
        (0.89, 0.412, 0.761), (0.565, 0.494, 0.863),
        (0.451, 0.369, 0.796), (0.322, 0.259, 0.58),
        (0.38, 0.408, 0.553), (0.518, 0.561, 0.741),
        (0.71, 0.784, 1), (0.584, 0.776, 1),
        (0.29, 0.565, 0.886), (0.094, 0.369, 0.69),
        (0.188, 0.529, 0.459), (0.145, 0.667, 0.557),
        (0.616, 0.871, 0.769), (0.765, 1, 0.576),
        (0.475, 0.812, 0.204), (0.302, 0.525, 0.114),
        (1, 0.725, 0), (0.996, 0.933, 0),
        (1, 0.976, 0.666), (0.976, 0.78, 0.263),
        (0.71, 0.518, 0.004), (0.573, 0.353, 0),
        (0.624, 0.329, 0.396), (1, 0.529, 0.624),
        (0.996, 0.682, 0.682), (0.98, 0.275, 0.275),
        (1, 0, 0), (0.8, 0.016, 0.016)
    ]

validate_palette_file(file_path, importing=True)

Validate if a file is a valid Houdini color palette file.

Parameters:

Name	Type	Description	Default
file_path	Union[str, Path]	Path to the palette file	required
importing	bool	Whether file is being imported (requires content)	True

Returns:

Type	Description
bool	True if file is valid, False if invalid

Notes

Valid palette files must: - Be named "opColorPalette.def" - Exist at the specified path - Contain content if importing=True

Example

validate_palette_file("path/to/opColorPalette.def") True

Source code in utils/colors.py

def validate_palette_file(file_path: Union[str, Path], importing: bool = True) -> bool:
    """Validate if a file is a valid Houdini color palette file.

    Args:
        file_path: Path to the palette file
        importing: Whether file is being imported (requires content)

    Returns:
        True if file is valid, False if invalid

    Notes:
        Valid palette files must:
        - Be named "opColorPalette.def"
        - Exist at the specified path
        - Contain content if importing=True

    Example:
        >>> validate_palette_file("path/to/opColorPalette.def")
        True
    """
    file_path = Path(file_path)
    if file_path.name != "opColorPalette.def":
        hou.ui.displayMessage("The selected file is not called opColorPalette.def, therefore it is not a Houdini node color palette file.")
        return False

    if not file_path.exists():
        hou.ui.displayMessage("The selected file does not exist. Use the 'Reset to Houdini Standard' button to populate the main list with the default colors.")
        return False

    if file_path.stat().st_size == 0 and not importing:
        hou.ui.displayMessage("The selected file is empty, so cannot import.")
        return False

    return True