Libraries for Simple Image Manipulation (Pillow, Scikit-image)

While generating highly realistic synthetic images often involves complex techniques like 3D rendering or Generative Adversarial Networks (GANs), many basic synthetic image tasks and augmentations can be accomplished using standard Python image processing libraries. These tools are excellent starting points for creating simple datasets or augmenting existing ones. Let's look at two popular choices: Pillow and Scikit-image.

Pillow: Your Go-To for Basic Image Handling

Pillow is a friendly fork of the original Python Imaging Library (PIL) and is widely used for opening, manipulating, and saving many different image file formats. For synthetic data generation, Pillow is particularly useful for:

• Creating Blank Images: You can easily generate images of a specific size and background color (e.g., a white canvas) to serve as a base.
• Drawing Simple Shapes: Pillow's ImageDraw module allows you to programmatically draw basic geometric shapes like rectangles, ellipses, lines, and polygons, or add text onto an image. This is great for creating simple datasets for object detection or classification tasks (e.g., images containing only squares or circles).
• Basic Transformations: Applying simple geometric transformations like rotating, resizing, cropping, or flipping images. While often used for data augmentation on real images, these techniques can also generate variations of simple synthetic images you've created.
• Color Manipulation: Adjusting brightness, contrast, or converting between color modes (e.g., RGB to grayscale).
• Pasting Images: Combining images by pasting one onto another, useful for creating composite scenes or placing synthetic objects onto backgrounds.

Think of Pillow as a digital canvas and paintbrush set for Python. It lets you build images from scratch using fundamental building blocks or modify existing ones with straightforward operations.

# Example: Creating a simple image with Pillow (Illustrative)
from PIL import Image, ImageDraw

# Create a 200x100 white canvas
img = Image.new('RGB', (200, 100), color = 'white')
d = ImageDraw.Draw(img)

# Draw a blue rectangle
d.rectangle([(20, 20), (80, 80)], fill='blue', outline='black')

# Draw red text
d.text((100, 50), "Simple Synth", fill='red')

# img.save('simple_synthetic_image.png') # Can save the image

Scikit-image: Leveraging NumPy for Image Processing

Scikit-image is part of the scientific Python ecosystem (alongside NumPy, SciPy, and Matplotlib) and provides a collection of algorithms for image processing. Its core strength lies in treating images as NumPy arrays, which integrates smoothly with other scientific libraries. For synthetic data, Scikit-image is useful for:

• Generating Noise: You can easily add various types of noise (e.g., Gaussian, salt & pepper, Poisson) to images. Adding noise can make synthetic images appear slightly more realistic or test the robustness of machine learning models.
• Applying Filters: Using filters for blurring (e.g., Gaussian blur), edge detection, or other effects. These can simulate different camera conditions or processing artifacts.
• Generating Shapes and Textures: While Pillow also draws shapes, Scikit-image offers functions to generate shapes or even procedural textures directly as NumPy arrays.
• Morphological Operations: Applying operations like dilation or erosion, which can modify the shapes of objects within an image.
• Segmentation and Feature Extraction: Although often used for analysis, these tools can sometimes be repurposed to help create synthetic masks or specific image features.

Scikit-image shines when you need to perform more algorithmic manipulations on the pixel data itself, leveraging the power of NumPy for numerical computation.

# Example: Adding noise with Scikit-image (Illustrative)
# Assume 'image_array' is a NumPy array representing an image
# (Could be loaded with skimage.io.imread or created with Pillow/NumPy)

# from skimage.util import random_noise
# import numpy as np

# Apply Gaussian noise
# noisy_image_array = random_noise(image_array, mode='gaussian', var=0.01)

# Convert back to standard pixel range if needed
# noisy_image_array = np.clip(noisy_image_array * 255, 0, 255).astype(np.uint8)

# Can then save this noisy_image_array using skimage.io.imsave or Pillow

Combining Tools

Often, you might use these libraries together. For instance, you could use Pillow to create a base image with simple shapes and then use Scikit-image to add specific types of noise or apply a blur filter.

A simple workflow combining Pillow and Scikit-image for basic synthetic image generation.

These libraries provide accessible entry points into programmatic image creation and manipulation. They are fundamental tools for generating the kinds of basic synthetic images and augmentations discussed earlier in this course, forming a stepping stone towards more advanced generation techniques.