Python Pillow - Resizing an Image

Resizing an image in Pillow Library involves changing the dimensions i.e. width and height of the image. This operation can be used to make an image larger or smaller and it can serve various purposes such as preparing images for display on a website, reducing file size or generating thumbnails.

Resizing an Image using the resize() method

In Pillow the resize() method is used to change the dimensions of an image. This function allows us to resize an image in the following ways.

• Absolute Dimensions − We can specify the new width and height in pixels to which the image should be resized.

• Maintaining Aspect Ratio − If We only specify one dimension either width or height then Pillow can automatically calculate the other dimension to maintain the image's aspect ratio.

• Scaling − We can resize the image by a scale factor which uniformly resizes both width and height while preserving the aspect ratio.

Here's the basic syntax for the resize() method −

PIL.Image.resize(size, resample=3)

Where,

• size − This can be either a tuple specifying the new width and height in pixels i.e. a single integer specifying the new size (width or height) or a float specifying a scaling factor.

• resample(optional) − The default value is 3 which corresponds to the anti-aliased high-quality filter. We can choose from various resampling filters such as Image.NEAREST, Image.BOX, Image.BILINEAR, Image.HAMMING, Image.BICUBIC, Image.LANCZOS, etc.

Following is the input image used in all the examples of this chapter.

Example - Resizing an Image

In this example we are using the resize() function for adjusting the width and height of the image by passing a tuple as input parameter.

main.py

from PIL import Image

#Open an image
image = Image.open("Images/rose.jpg")

#Resize to specific dimensions (e.g., 300x200 pixels)
new_size = (300, 200)
resized_image = image.resize(new_size)

#Display resized image
resized_image.show()

Output

Example - Resizing an Image with maintaining Aspect Ratio

Here in this example we are resizing the image by maintaining the same aspect ratio of the original input image.

from PIL import Image

#Open an image
image = Image.open("Images/rose.jpg")

#Resize by maintaining aspect ratio (e.g., specify the width)
new_width = 200
aspect_ratio_preserved = image.resize((new_width, int(image.height * (new_width / image.width))))
aspect_ratio_preserved.show()

Output

Example - Resizing with Scale Factor

In this example we are resizing the image with the scale by factor.

main.py

from PIL import Image

#Open an image
image = Image.open("Images/rose.jpg")

#Scale the image by a factor (e.g., 10% of the original size)
scaling_factor = 0.1
scaled_image = image.resize((int(image.width * scaling_factor), int(image.height * scaling_factor)))
scaled_image.show()

Output