Wand black_threshold() function - Python

Last Updated : 08 Aug, 2022

The black_threshold() function is an inbuilt function in the Python Wand ImageMagick library which is used to force all pixels above a given color as black and leaves all pixels above threshold unaltered.

Syntax:
black_threshold(color)
Parameters: This function accepts single parameter as mentioned above and defined below:

color: This parameter is used to specify the value of factor in order to apply black threshold. This parameter accepts values as color strings like 'Green', 'Blue', 'Red', 'White' etc.

Return Value: This function returns the Wand ImageMagick object.

Original Image:

Example 1:

Python3

# Import library from Image 
from wand.image import Image

# Import the image
with Image(filename ='../geeksforgeeks.png') as image:
    # Clone the image in order to process
    with image.clone() as black_threshold:
        # Invoke black_threshold function with threshold parameter as 'Green'
        black_threshold.black_threshold('Green')
        # Save the image
        black_threshold.save(filename ='black_threshold1.jpg')

Output:

Example 2:

Python3

# Import libraries from the wand  
from wand.image import Image
from wand.drawing import Drawing
from wand.color import Color

with Drawing() as draw:
    # Set Stroke color the circle to black
    draw.stroke_color = Color('black')
    # Set Width of the circle to 2 
    draw.stroke_width = 1
    # Set the fill color to 'White (# FFFFFF)'
    draw.fill_color = Color('white')

    # Invoke Circle function with center at 50, 50 and radius 25
    draw.circle((200, 200), # Center point
                (100, 100)) # Perimeter point
    # Set the font style
    draw.font = '../Helvetica.ttf'
    # Set the font size 
    draw.font_size = 30
    
    with Image(width = 400, height = 400, background = Color('# 45ff33')) as pic:
        # Set the text and its location
        draw.text(int(pic.width / 3), int(pic.height / 2), 'GeeksForGeeks !')
        # Draw the picture
        draw(pic)
        # Invoke black_threshold function with threshold parameter as 'White'
        pic.black_threshold('White')
        # Save the image 
        pic.save(filename ='black_threshold2.jpg')