Configuration and Customization

# Font configuration
CAPTCHA_FONT_PATH = '/path/to/font.ttf'  # str or list of font paths
CAPTCHA_FONT_SIZE = 22                   # int, font size in points

# Image styling
CAPTCHA_BACKGROUND_COLOR = '#ffffff'     # str, hex color for background
CAPTCHA_FOREGROUND_COLOR = '#001100'     # str, hex color for text
CAPTCHA_LETTER_ROTATION = (-35, 35)      # tuple, rotation range in degrees
CAPTCHA_IMAGE_SIZE = None                # tuple, fixed (width, height) or None for auto

# High-resolution support
CAPTCHA_2X_IMAGE = True                  # bool, enable 2x resolution images

# Challenge type and length
CAPTCHA_CHALLENGE_FUNCT = 'captcha.helpers.random_char_challenge'  # str or callable
CAPTCHA_LENGTH = 4                       # int, challenge text length

# Dictionary-based challenges  
CAPTCHA_WORDS_DICTIONARY = '/usr/share/dict/words'  # str, path to word list file
CAPTCHA_DICTIONARY_MIN_LENGTH = 0        # int, minimum word length
CAPTCHA_DICTIONARY_MAX_LENGTH = 999      # int, maximum word length
CAPTCHA_PUNCTUATION = '.,;:'             # str, punctuation for word challenges

# Math challenge customization
CAPTCHA_MATH_CHALLENGE_OPERATOR = '*'    # str, display operator in math challenges

# Noise and filter functions
CAPTCHA_NOISE_FUNCTIONS = (              # tuple of noise function names/callables
    'captcha.helpers.noise_arcs',
    'captcha.helpers.noise_dots',
)
CAPTCHA_FILTER_FUNCTIONS = (             # tuple of filter function names/callables
    'captcha.helpers.post_smooth',
)

# Custom color function
CAPTCHA_LETTER_COLOR_FUNCT = None        # str or callable for custom letter coloring

# Expiration and lifecycle
CAPTCHA_TIMEOUT = 5                      # int, expiration timeout in minutes

# Performance optimization
CAPTCHA_GET_FROM_POOL = False            # bool, use pre-generated captcha pool
CAPTCHA_GET_FROM_POOL_TIMEOUT = 5        # int, pool timeout in minutes

# Testing and development
CAPTCHA_TEST_MODE = False                # bool, disable validation for testing

# Audio generation paths
CAPTCHA_FLITE_PATH = '/usr/bin/flite'    # str, path to flite text-to-speech binary
CAPTCHA_SOX_PATH = '/usr/bin/sox'        # str, path to sox audio processing binary

def math_challenge():
    """
    Generate simple arithmetic problems (addition, subtraction, multiplication).
    
    Returns:
    tuple: (challenge_text, expected_response)
    
    Example: ('2 + 3 = ?', '5')
    """

def random_char_challenge():
    """
    Generate random alphanumeric character string.
    
    Returns:
    tuple: (challenge_text, expected_response)
    
    Example: ('AB3F', 'AB3F')
    """

def unicode_challenge():
    """
    Generate challenge using unicode characters.
    
    Returns:
    tuple: (challenge_text, expected_response)
    """

def word_challenge():
    """
    Generate challenge using dictionary words.
    
    Returns:
    tuple: (challenge_text, expected_response)
    
    Requires: CAPTCHA_WORDS_DICTIONARY setting
    """

def huge_words_and_punctuation_challenge():
    """
    Generate challenge with large words and punctuation.
    
    Returns:
    tuple: (challenge_text, expected_response)
    """

def random_letter_color_challenge(idx, plaintext_captcha):
    """
    Generate random color for individual letters in captcha.
    
    Parameters:
    - idx: int, letter index in the captcha
    - plaintext_captcha: str, the complete captcha text
    
    Returns:
    str: Hex color string (e.g., "#FF5733")
    """

def noise_arcs(draw, image):
    """
    Add curved arc noise to captcha image.
    
    Parameters:
    - draw: PIL ImageDraw object
    - image: PIL Image object
    """

def noise_dots(draw, image):
    """
    Add random dot noise to captcha image.
    
    Parameters:
    - draw: PIL ImageDraw object
    - image: PIL Image object
    """

def noise_null(draw, image):
    """
    No-operation noise function (no visual noise added).
    
    Parameters:
    - draw: PIL ImageDraw object
    - image: PIL Image object
    """

def post_smooth(image):
    """
    Apply smoothing filter to reduce image harshness.
    
    Parameters:
    - image: PIL Image object
    
    Returns:
    PIL.Image: Filtered image
    """

def _callable_from_string(string_or_callable):
    """
    Import callable from string module path.
    
    Parameters:
    - string_or_callable: str or callable
    
    Returns:
    callable: Imported function or original callable
    """

def get_challenge(generator=None):
    """
    Get challenge generator function from settings or parameter.
    
    Parameters:
    - generator: str or callable, override default generator (optional)
    
    Returns:
    callable: Challenge generator function
    """

def noise_functions():
    """
    Get configured noise function generators.
    
    Returns:
    list: List of noise function callables
    """

def filter_functions():
    """
    Get configured filter function generators.
    
    Returns:
    list: List of filter function callables
    """

def get_letter_color(index, challenge):
    """
    Get color for specific letter in challenge.
    
    Parameters:
    - index: int, letter position in challenge
    - challenge: str, complete challenge text
    
    Returns:
    str: Color value for the letter
    """

# In settings.py
CAPTCHA_FONT_SIZE = 24
CAPTCHA_LENGTH = 6
CAPTCHA_TIMEOUT = 10  # 10 minutes
CAPTCHA_BACKGROUND_COLOR = '#f0f0f0'
CAPTCHA_FOREGROUND_COLOR = '#333333'

# Use math challenges instead of random text
CAPTCHA_CHALLENGE_FUNCT = 'captcha.helpers.math_challenge'
CAPTCHA_MATH_CHALLENGE_OPERATOR = '+'
CAPTCHA_LENGTH = 1  # Not used for math challenges

# Use dictionary words for challenges
CAPTCHA_CHALLENGE_FUNCT = 'captcha.helpers.word_challenge'
CAPTCHA_WORDS_DICTIONARY = '/usr/share/dict/words'
CAPTCHA_DICTIONARY_MIN_LENGTH = 4
CAPTCHA_DICTIONARY_MAX_LENGTH = 8

# Add more visual noise
CAPTCHA_NOISE_FUNCTIONS = (
    'captcha.helpers.noise_arcs',
    'captcha.helpers.noise_dots',
    'captcha.helpers.noise_dots',  # Apply dots twice for more noise
)

# Apply smoothing filter
CAPTCHA_FILTER_FUNCTIONS = (
    'captcha.helpers.post_smooth',
)

# Enable captcha pool for high-traffic sites
CAPTCHA_GET_FROM_POOL = True
CAPTCHA_GET_FROM_POOL_TIMEOUT = 10

# Longer expiration time
CAPTCHA_TIMEOUT = 15  # 15 minutes

# Enable audio captcha with custom paths
CAPTCHA_FLITE_PATH = '/opt/flite/bin/flite'
CAPTCHA_SOX_PATH = '/opt/sox/bin/sox'

# Create custom challenge function
def custom_challenge():
    import random
    import string
    
    # Generate uppercase letters only
    chars = ''.join(random.choices(string.ascii_uppercase, k=5))
    return chars, chars

# Use custom challenge
CAPTCHA_CHALLENGE_FUNCT = 'myapp.utils.custom_challenge'

# Disable captcha validation for testing
CAPTCHA_TEST_MODE = True  # Only use in development/testing!