Pillow Image Basic Operations

After installing the Pillow library, we need to import the necessary modules:

# 导入模块
from PIL import Image, ImageFilter, ImageEnhance, ImageDraw, ImageFont
import os

Test image (download to local for testing):

Example

The following is a complete example demonstrating the following operations:

  1. Open and display basic image information
    • Format, size, mode, etc.
  2. Resize image
    • Resize image to specified dimensions
  3. Crop image
    • Extract a specific region from the original image
  4. Rotate image
    • Rotate 45 degrees and keep the entire image
  5. Flip image
    • Horizontal and vertical flip
  6. Convert color mode
    • Convert color image to grayscale
  7. Apply filters
    • Effects such as blur, edge enhancement, contour, etc.
  8. Adjust image properties
    • Brightness, contrast, and sharpness adjustment
  9. Add text
    • Draw text on the image
  10. Merge images
    • Simple image stitching
  11. Save in different formats and qualities
    • PNG, BMP, and JPEG of different qualities

Example

"""
Python Pillow Image Basic Operations Tutorial
Test image used: tiger.jpeg
"""

from PIL import Image, ImageFilter, ImageEnhance, ImageDraw, ImageFont
import os

def main():
    # Ensure there is an output folder in our working directory
    output_dir = "output"
    if not os.path.exists(output_dir):
        os.makedirs(output_dir)
   
    # 1. Open image
    print("1. Open image")
    try:
        img = Image.open("tiger.jpeg")
        print(f"Successfully opened image - Format: {img.format}, Size: {img.size}, Mode: {img.mode}")
    except Exception as e:
        print(f"Unable to open image: {e}")
        return
   
    # 2. Display basic image information
    print("\n2. Basic image information")
    print(f"Image format: {img.format}")
    print(f"Image size (width x height): {img.size}")
    print(f"Image mode: {img.mode}")
   
    # 3. Resize image
    print("\n3. Resize image")
    resized_img = img.resize((400, 300))
    resized_img.save(f"{output_dir}/resized_tiger.jpg")
    print("Saved the resized image")
   
    # 4. Crop image
    print("\n4. Crop image")
    # Crop area (left, top, right, bottom)
    width, height = img.size
    crop_area = (width//4, height//4, 3*width//4, 3*height//4)  # Crop the middle area
    cropped_img = img.crop(crop_area)
    cropped_img.save(f"{output_dir}/cropped_tiger.jpg")
    print(f"Cropped image area {crop_area} and saved")
   
    # 5. Rotate image
    print("\n5. Rotate image")
    rotated_img = img.rotate(45, expand=True)  # Rotate 45 degrees, expand=True keeps the entire image
    rotated_img.save(f"{output_dir}/rotated_tiger.jpg")
    print("Saved the rotated image")
   
    # 6. Flip image
    print("\n6. Flip image")
    # Horizontal flip
    h_flipped = img.transpose(Image.FLIP_LEFT_RIGHT)
    h_flipped.save(f"{output_dir}/horizontal_flip_tiger.jpg")
    # Vertical flip
    v_flipped = img.transpose(Image.FLIP_TOP_BOTTOM)
    v_flipped.save(f"{output_dir}/vertical_flip_tiger.jpg")
    print("Saved the horizontally and vertically flipped images")
   
    # 7. Convert color mode
    print("\n7. Convert color mode")
    grayscale_img = img.convert('L')  # Convert to grayscale
    grayscale_img.save(f"{output_dir}/grayscale_tiger.jpg")
    print("Saved the grayscale image")
   
    # 8. Apply filters
    print("\n8. Apply filters")
    # Blur filter
    blurred_img = img.filter(ImageFilter.BLUR)
    blurred_img.save(f"{output_dir}/blurred_tiger.jpg")
    # Edge enhancement
    edge_img = img.filter(ImageFilter.EDGE_ENHANCE)
    edge_img.save(f"{output_dir}/edge_enhanced_tiger.jpg")
    # Contour filter
    contour_img = img.filter(ImageFilter.CONTOUR)
    contour_img.save(f"{output_dir}/contour_tiger.jpg")
    print("Saved images with different filters applied")
   
    # 9. Adjust brightness, contrast, and sharpness
    print("\n9. Adjust image properties")
    # Increase brightness
    brightness = ImageEnhance.Brightness(img)
    bright_img = brightness.enhance(1.5)  # Brightness increased by 50%
    bright_img.save(f"{output_dir}/brighter_tiger.jpg")
   
    # Increase contrast
    contrast = ImageEnhance.Contrast(img)
    contrast_img = contrast.enhance(1.5)  # Contrast increased by 50%
    contrast_img.save(f"{output_dir}/contrast_tiger.jpg")
   
    # Increase sharpness
    sharpness = ImageEnhance.Sharpness(img)
    sharp_img = sharpness.enhance(2.0)  # Sharpness increased by 100%
    sharp_img.save(f"{output_dir}/sharper_tiger.jpg")
    print("Saved the image after brightness, contrast, and sharpness adjustments")
   
    # 10. Add text
    print("\n10. Add text")
    # Create a copy for drawing
    text_img = img.copy()
    draw = ImageDraw.Draw(text_img)
    # Try to use a system font, fall back to default if it fails
    try:
        # Different operating systems may require different font paths
        # Windows font path example
        font = ImageFont.truetype("arial.ttf", 36)
    except IOError:
        font = ImageFont.load_default()
   
    # Add text to the image
    draw.text((10, 10), "Tiger", fill=(255, 255, 255), font=font)
    text_img.save(f"{output_dir}/text_tiger.jpg")
    print("Saved the image with added text")
   
    # 11. Merge images (simple stitching)
    print("\n11. Merge images")
    # Create a new image with twice the width of the original and the same height
    merged_img = Image.new('RGB', (width*2, height))
    # Place the original image on the left
    merged_img.paste(img, (0, 0))
    # Place the grayscale image on the right
    merged_img.paste(grayscale_img.convert('RGB'), (width, 0))
    merged_img.save(f"{output_dir}/merged_tiger.jpg")
    print("Saved the merged image")
   
    # 12. Save in different formats
    print("\n12. Save in different formats")
    img.save(f"{output_dir}/tiger.png")  # PNG format
    img.save(f"{output_dir}/tiger.bmp")  # BMP format
   
    # Save as JPEG with quality setting
    img.save(f"{output_dir}/tiger_high_quality.jpg", quality=95)  # High quality
    img.save(f"{output_dir}/tiger_low_quality.jpg", quality=10)   # Low quality
    print("Saved images in different formats and qualities")
   
    print("\nAll operations completed! The processed images are saved in the 'output' folder.")

if __name__ == "__main__":
    main()

The code uses a structured approach, with clear comments for each operation. All processed images are saved inoutputdirectory for easy viewing and comparison of results.

Usage:

  • Make sure the tiger.jpeg image is in the same directory as the code
  • Run the code, and various processed images will be generated in the output folder
  • View the different processing effects based on the output information

If the above code executes successfully, the terminal output will be:

Operation Description

1. Open image and get basic information

Example

# Open image file
img = Image.open("tiger.jpeg")

# Get and display image information
print(f"Image format: {img.format}")  # e.g., JPEG, PNG, etc.
print(f"Image size (width x height): {img.size}")  # e.g., (800, 600)
print(f"Image mode: {img.mode}")  # e.g., RGB, RGBA, L (grayscale), etc.

Detailed Explanation：

  • Image.open()The function is used to open an image file, and the parameter is the path to the image file.
  • img.formatDisplay the image format (e.g., JPEG, PNG, GIF, etc.)
  • img.sizeReturns a tuple containing width and height, e.g., (800, 600)
  • img.modeDisplay the color mode of the image:
    • RGB: Color image
    • RGBA: Color image with transparency channel
    • L: Grayscale image
    • 1: Binary image (black and white)

2. Resize image

Example

# Resize image to 400x300 pixels
resized_img = img.resize((400, 300))

# Save the resized image
resized_img.save("output/resized_tiger.jpg")

Detailed Explanation：

  • resize()The method is used to change the image size, and the parameter is a tuple containing the new width and height.
  • This method does not modify the original image, but returns a new image object.
  • By default, nearest-neighbor interpolation is used. For higher-quality resizing, you can add parameters:resized_img = img.resize((400, 300), Image.LANCZOS)
  • save()The method saves the processed image to the specified path.

3. Crop image

Example

# Get the original image size
width, height = img.size

# Define the crop area (left, top, right, bottom)
crop_area = (width//4, height//4, 3*width//4, 3*height//4)  # Crop the middle area

# Perform the crop
cropped_img = img.crop(crop_area)

# Save the cropped image
cropped_img.save("output/cropped_tiger.jpg")

Detailed Explanation：

  • crop()The method is used to extract a rectangular region from the image.
  • The crop area is defined by a tuple(left, upper, right, lower)Definition:
    • left: x-coordinate of the left boundary
    • upper: y-coordinate of the top boundary
    • right: x-coordinate of the right boundary
    • lower: y-coordinate of the bottom boundary
  • In the example, we cropped the central part of the image (the 1/4 to 3/4 region)
  • width//4in//is integer division, ensuring the result is an integer

4. Rotate image

Example

# Rotate the image 45 degrees and expand the canvas to show the full image
rotated_img = img.rotate(45, expand=True)

# Save the rotated image
rotated_img.save("output/rotated_tiger.jpg")

Detailed Explanation：

  • rotate()The method is used to rotate the image; the first parameter is the rotation angle (counterclockwise, in degrees)
  • expand=TrueThe parameter expands the size of the output image to accommodate the entire rotated image
  • If not setexpand=True, the rotated image will be cropped to fit the original size
  • By default, the rotation center is the center point of the image

5. Flip image

Example

# Horizontal flip (left-right mirror)
h_flipped = img.transpose(Image.FLIP_LEFT_RIGHT)
h_flipped.save("output/horizontal_flip_tiger.jpg")

# Vertical flip (top-bottom mirror)
v_flipped = img.transpose(Image.FLIP_TOP_BOTTOM)
v_flipped.save("output/vertical_flip_tiger.jpg")

Detailed Explanation：

  • transpose()The method is used for image flip and transpose operations
  • Image.FLIP_LEFT_RIGHTThe constant represents horizontal flip (left-right mirror)
  • Image.FLIP_TOP_BOTTOMThe constant represents vertical flip (top-bottom mirror)
  • In addition to flipping, other constants such as can also be usedImage.ROTATE_90, Image.ROTATE_180, Image.ROTATE_270to perform rotation

6. Convert color mode

Example

# Convert the image to grayscale
grayscale_img = img.convert('L')

# Save the grayscale image
grayscale_img.save("output/grayscale_tiger.jpg")

Detailed Explanation：

  • convert()The method is used to change the image mode (color space)
  • The parameter'L'indicates conversion to a grayscale image (Luminance)
  • Other commonly used modes include:
    • 'RGB': three-channel color
    • 'RGBA': four-channel color (with transparency)
    • 'CMYK': CMYK four-color printing mode
    • '1': binary image (pure black and white)
  • Converting modes can reduce file size or prepare for specific processing

7. Apply image filters

Example

# Apply a blur filter
blurred_img = img.filter(ImageFilter.BLUR)
blurred_img.save("output/blurred_tiger.jpg")

# Apply an edge enhancement filter
edge_img = img.filter(ImageFilter.EDGE_ENHANCE)
edge_img.save("output/edge_enhanced_tiger.jpg")

# Apply a contour filter
contour_img = img.filter(ImageFilter.CONTOUR)
contour_img.save("output/contour_tiger.jpg")

Detailed Explanation：

  • filter()The method is used to apply various predefined filter effects to an image
  • ImageFilter.BLURIt blurs the image, similar to a soft-focus effect
  • ImageFilter.EDGE_ENHANCEEnhances the edges of the image, making contours more visible
  • ImageFilter.CONTOURFinds the contour lines of the image, producing a sketch-like effect
  • Other commonly used filters include:
    • ImageFilter.SHARPEN: Sharpen the image
    • ImageFilter.EMBOSS: Emboss effect
    • ImageFilter.FIND_EDGES: Find edges
    • ImageFilter.SMOOTH: Smooth the image
  • You can also create custom filters, such as Gaussian blur:img.filter(ImageFilter.GaussianBlur(radius=2))

8. Adjust image properties (brightness, contrast, sharpness)

Example

# Increase brightness (1.5 means brightness increased by 50%)
brightness = ImageEnhance.Brightness(img)
bright_img = brightness.enhance(1.5)
bright_img.save("output/brighter_tiger.jpg")

# Increase contrast (1.5 means contrast increased by 50%)
contrast = ImageEnhance.Contrast(img)
contrast_img = contrast.enhance(1.5)
contrast_img.save("output/contrast_tiger.jpg")

# Increase sharpness (2.0 means sharpness increased by 100%)
sharpness = ImageEnhance.Sharpness(img)
sharp_img = sharpness.enhance(2.0)
sharp_img.save("output/sharper_tiger.jpg")

Detailed Explanation：

  • ImageEnhanceThe module provides several enhancer classes for adjusting different image properties
  • Each enhancer must first be initialized with an image object
  • enhance()The method accepts a parameter indicating the degree of enhancement:
    • A value of 1.0 means the original image remains unchanged
    • A value greater than 1.0 indicates an enhancement effect (e.g., 1.5 means an increase of 50%)
    • A value less than 1.0 indicates a reduction effect (e.g., 0.5 means a decrease of 50%)
  • In addition to the three enhancers shown above, there is alsoImageEnhance.Colorfor adjusting color saturation

9. Add text to image

Example

# Create a copy of the image for drawing
text_img = img.copy()

# Create a drawing object
draw = ImageDraw.Draw(text_img)

# Try to load a font (use default font if unavailable)
try:
    # Load a system font with size 36 pixels
    font = ImageFont.truetype("arial.ttf", 36)
except IOError:
    # If the specified font is not found, use the default font
    font = ImageFont.load_default()

# Add text to the image
draw.text((10, 10), "Tiger", fill=(255, 255, 255), font=font)

# Save the image with the added text
text_img.save("output/text_tiger.jpg")

Detailed Explanation：

  • copy()The method creates a copy of the original image to avoid modifying the original image
  • ImageDraw.Draw()Creates a drawing object for drawing on the image
  • ImageFont.truetype()Used to load TrueType fonts:
    • The first parameter is the font file path (e.g., "arial.ttf")
    • The second parameter is the font size (in pixels)
  • draw.text()Used to draw text on the image:
    • The first parameter(10, 10)is the position coordinates of the text (top-left corner)
    • The second parameter is the text content to be drawn
    • fillThe parameter specifies the text color, here it is white(255, 255, 255)
    • fontThe parameter specifies the font to use
  • Usetry-exceptblock to handle possible font loading failures

10. Merge images (simple stitching)

Example

# Get the original image size
width, height = img.size

# Create a new blank image with twice the width of the original
merged_img = Image.new('RGB', (width*2, height))

# Paste the original image on the left
merged_img.paste(img, (0, 0))

# Convert the grayscale image to RGB and paste it on the right
merged_img.paste(grayscale_img.convert('RGB'), (width, 0))

# Save the merged image
merged_img.save("output/merged_tiger.jpg")

Detailed Explanation：

  • Image.new()Create a new blank image:
    • The first parameter is the color mode, here it is'RGB'
    • The second parameter is the image size, here it is twice the original width and the original height
  • paste()The method pastes one image onto another:
    • The first parameter is the image to be pasted
    • The second parameter is the coordinates of the paste position (top-left corner)
  • convert('RGB')Convert the grayscale image to RGB mode because only images of the same mode can be pasted together
  • This method can be used to create collages, side-by-side comparisons, or photo collections

11. Save in different formats and qualities

Example

# Save as PNG format (lossless compression)
img.save("output/tiger.png")

# Save as BMP format (no compression)
img.save("output/tiger.bmp")

# Save as high-quality JPEG (quality 95%)
img.save("output/tiger_high_quality.jpg", quality=95)

# Save as low-quality JPEG (quality 10%)
img.save("output/tiger_low_quality.jpg", quality=10)

Detailed Explanation：

  • save()The method automatically determines the save format based on the file extension
  • Characteristics of different formats:
    • PNG: Lossless compression, supports transparency, suitable for icons, screenshots, etc.
    • JPEG: Lossy compression, suitable for photos, does not support transparency
    • BMP: No compression, larger file size, but retains all information
    • GIF: Supports animation, up to 256 colors
  • For JPEG format, you can use thequalityparameter to control compression quality:
    • The value ranges from 1 (worst quality, smallest file) to 95 (best quality, larger file)
    • The default value is usually 75
  • Different quality settings can help balance image quality and file size

12. Create output directory

Example

# Ensure the output directory exists
output_dir = "output"
if not os.path.exists(output_dir):
    os.makedirs(output_dir)

Detailed Explanation：

  • os.path.exists()Check whether the specified directory exists
  • os.makedirs()Create the directory if it does not exist
  • This code ensures we have a place to save the processed images
  • Putting all generated images in a separate directory can better organize the project
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