This blog will walk you through how to convert an Image to Pencil Sketch using Python, explain how the process works, and show you the complete code implementation.
Fortunately, with Python and the OpenCV library, achieving this effect is both simple and efficient.
Working of Pencil Sketch in Python Library
Before jumping into the code, it’s important to understand how this transformation happens.
When we think of a pencil sketch, we imagine a grayscale drawing with high contrast, primarily showing the outlines and textures of the image.
To replicate, We use steps in image processing.
The first step is converting the image to grayscale, which removes all color information and simplifies the visual data.
Next, we invert the grayscale image so that dark areas become light and light areas become dark. This is necessary for the next step, where we apply a Gaussian blur.
Once we have the blurred image, we invert it again and blend it with the original grayscale image using a technique called “dodge blending.”
In OpenCV, this is done using the cv2.divide() function. This combination of operations results in an image that closely resembles a hand-drawn pencil sketch.
Code to Convert an Image to Pencil Sketch using Python
Here is the complete Python script that performs the sketch transformation:
import cv2
# Load the image from the specified path
image1 = cv2.imread('E:\\demo.png')
window_name = 'Original image'
cv2.imshow(window_name, image1)
# Convert the image to grayscale
grey_img = cv2.cvtColor(image1, cv2.COLOR_BGR2GRAY)
# Invert the grayscale image
invert = cv2.bitwise_not(grey_img)
# Apply Gaussian Blur to the inverted image
blur = cv2.GaussianBlur(invert, (21, 21), 0)
# Invert the blurred image
invertedblur = cv2.bitwise_not(blur)
# Create the sketch using divide blend
sketch = cv2.divide(grey_img, invertedblur, scale=256.0)
# Save the result to a file
cv2.imwrite("E:\\sketch.png", sketch)
# Load and display the sketch image
image = cv2.imread("E:\\sketch.png")
window_name = 'Sketch image'
cv2.imshow(window_name, image)
# Wait for a key press and close all windows
cv2.waitKey(0)
cv2.destroyAllWindows()
This code reads an image, applies all the transformation steps explained earlier, and saves the final sketch image on your system. It also displays both the original and the sketch images in separate windows for visual comparison.
Applications of Pencil Sketch Effects
This pencil sketch effect is more than just a fun transformation. It has practical applications in mobile photography apps, digital portfolios, and even in automated image editing pipelines.
With some enhancements, this script can be integrated into a user interface, used for batch processing multiple images, or extended to apply other effects like color sketches or cartoon filters.
Conclusion
This project is a great starting point for anyone interested in working with images or enhancing their Python skills through practical, visual applications. There are various such python projects here.
Try experimenting with different blur levels or image types and observe how the sketch quality changes. You’ll be surprised at how much control and creativity you can unlock with just a few lines of code.
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