魔杖 black_threshold()函数- Python

black_threshold()函数是Python Wand ImageMagick 库中的一个内置函数，用于强制高于给定颜色的所有像素为黑色，并使高于阈值的所有像素保持不变。

Syntax: 
 

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.

原图：

示例 1：

Python3

black_threshold(color)

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')

输出：

示例 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 with threshold parameter as 'White'
        pic.black_threshold('White')
        # Save the image
        pic.save(filename ='black_threshold2.jpg')

输出：