Picture Resizing utilizing OpenCV Utilizing Python



Picture resizing is a vital activity in pc imaginative and prescient that includes altering the size of a picture whereas sustaining its side ratio. It’s basic in varied functions, together with internet improvement, pc imaginative and prescient duties, and machine studying fashions. On this article, we’ll discover completely different image-resizing methods utilizing OpenCV, a preferred library for pc imaginative and prescient duties in Python.

Picture resizing performs a significant function in pc imaginative and prescient functions. It permits us to regulate the dimensions of pictures to satisfy particular necessities, equivalent to becoming pictures into an internet web page structure, making ready pictures for machine studying fashions, or resizing pictures for pc imaginative and prescient duties like object detection and recognition.

Image Resizing using OpenCV _ Python

How-To: Picture Resizing in Python utilizing OpenCV

Comply with this step-by-step information to resize pictures effortlessly utilizing OpenCV in Python:

  1. Putting in OpenCV and Required Libraries.

    Start by putting in the OpenCV library and any further required libraries. OpenCV could be put in utilizing package deal managers like pip.

  2. Loading and Displaying an Picture

    Import the OpenCV library in your Python script and use the cv2.imread() operate to load a picture from a file. Show the loaded picture utilizing cv2.imshow(), and don’t neglect to incorporate cv2.waitKey(0) to make sure the picture window stays open till you press a key.

  3. Resizing an Picture

    Make the most of the cv2.resize() operate to resize the loaded picture. Specify the specified dimensions (width and top) as parameters.

  4. Saving the Resized Picture

    After resizing the picture, reserve it to a brand new file utilizing the cv2.imwrite() operate. Present the filename and the resized picture as parameters.

Within the subsequent part, we’ll focus on this extra totally.

Picture Resizing Course of in Python utilizing OpenCV

Now, let’s dive into the sensible implementation of picture resizing utilizing OpenCV in Python. Comply with the steps under:

Putting in OpenCV and Required Libraries

Earlier than we start, be sure you have OpenCV put in in your system. You’ll be able to set up it utilizing pip:


pip set up opencv-python

Moreover, it’s possible you’ll want to put in different libraries, equivalent to NumPy, for picture manipulation duties.

Loading and Displaying an Picture

To resize a picture, we first must load it into our Python script. OpenCV supplies the `imread` operate to learn a picture from a file. We are able to then show the picture utilizing the `imshow` operate.


import cv2
# Load the picture
picture = cv2.imread('picture.jpg')
# Show the picture
cv2.imshow('Authentic Picture', picture)

Resizing an Picture

To resize the picture, we will use OpenCV’s `resize` operate. We should specify the unique picture, goal dimensions, and interpolation technique as enter parameters.


# Resize the picture
resized_image = cv2.resize(picture, (new_width, new_height), interpolation=cv2.INTER_LINEAR)

Saving the Resized Picture

After resizing the picture, we will reserve it to a file utilizing the `imwrite` operate.


# Save the resized picture
cv2.imwrite('resized_image.jpg', resized_image)

Picture Resizing Strategies in OpenCV

OpenCV supplies a number of methods for resizing pictures, every serving completely different functions. Let’s discover among the generally used methods:

Resizing by Scaling

Resizing a picture by scaling includes multiplying the width and top of the picture by a scaling issue. This method permits us to extend or lower the dimensions of a picture whereas sustaining its side ratio. OpenCV supplies the `resize` operate, which takes the unique picture and the specified dimensions as enter parameters.

Resizing with Facet Ratio Preservation

Preserving the side ratio of a picture is essential to keep away from distortion. OpenCV supplies a handy technique to resize pictures whereas preserving their side ratio. By specifying the specified width or top, OpenCV robotically adjusts the opposite dimension to keep up the side ratio.

Resizing with Customized Dimensions

In some instances, we might must resize a picture to particular customized dimensions. OpenCV permits us to resize pictures to any desired width and top by specifying the goal dimensions explicitly.

Resizing utilizing Interpolation Strategies

Interpolation strategies are used to estimate pixel values when resizing a picture. OpenCV supplies varied interpolation strategies, equivalent to nearest-neighbor, bilinear, and bicubic interpolation. These strategies assist in preserving picture high quality and decreasing artifacts in the course of the resizing course of.

Frequent Challenges and Concerns in Picture Resizing

Whereas resizing pictures, we should take into account sure challenges and keep picture high quality. Let’s focus on some frequent challenges:

  • Sustaining Picture High quality and Facet Ratio: Sustaining picture high quality and side ratio is essential to keep away from distortion and artifacts. We are able to guarantee high-quality resized pictures utilizing acceptable interpolation strategies and preserving the side ratio.
  • Dealing with Completely different Picture Codecs: Photographs could be in varied codecs, equivalent to JPEG, PNG, or BMP. Dealing with completely different picture codecs appropriately throughout resizing is important to keep away from compatibility points.
  • Coping with Reminiscence Constraints: Resizing giant pictures can eat important reminiscence. It’s important to optimize the resizing course of to deal with reminiscence constraints effectively, particularly when working with restricted assets.

Superior Picture Resizing Strategies in OpenCV

OpenCV presents superior picture resizing methods that transcend easy scaling. Let’s discover a few of these methods:

Content material-Conscious Picture Resizing

Content material-aware picture resizing is a classy method that goals to resize pictures whereas preserving vital content material and constructions, adapting the resizing course of to the picture’s content material.

  1. Preservation of Content material: Not like conventional resizing strategies which will distort or crop vital components, content-aware resizing intelligently identifies and preserves areas of excessive significance within the picture.
  2. Seam Carving Algorithm: One of many widespread approaches to content-aware resizing is the Seam Carving algorithm, which was briefly talked about within the article. Seam carving identifies and removes or provides seams (paths of pixels) with low significance, permitting for non-uniform resizing.
  3. Adaptive Resizing: Content material-aware resizing adapts the resizing operation primarily based on the picture’s content material. It might cut back the dimensions of much less vital areas whereas sustaining the integrity of great objects or constructions.
  4. Functions: Content material-aware resizing is especially helpful in eventualities the place preserving the content material and construction of the picture is essential. It finds functions in pictures, graphic design, and internet improvement the place sustaining the visible integrity of pictures throughout resizing is vital.
  5. Artifact Discount: Much like seam carving, content-aware resizing helps cut back artifacts which will happen in conventional resizing strategies, guaranteeing a extra visually pleasing outcome.
  6. Consumer Steering: Some content-aware resizing instruments permit customers to information the resizing course of by specifying areas of the picture that needs to be preserved or eliminated. This interactive method supplies extra management over the ultimate outcome.
  7. Limitations: Whereas content-aware resizing is highly effective, it could face challenges in sure pictures or advanced scenes. The effectiveness depends upon the algorithm used and the power to precisely establish the significance of various picture areas.

Seam Carving for Picture Resizing

Seam carving is a complicated image-resizing method that goes past conventional scaling. Not like conventional strategies that uniformly resize a picture, seam carving goals to intelligently resize pictures by eradicating or including seams, that are paths of pixels with low power.

  1. Power Map: The power of a pixel represents its significance within the picture. An power map is created by computing the gradient of the picture, highlighting areas with excessive distinction and vital options.
  2. Dynamic Programming: Seam carving makes use of dynamic programming to search out the optimum seam (path) to take away or duplicate within the picture. The seam with the bottom gathered power is taken into account, guaranteeing that vital options are preserved.
  3. Non-Uniform Resizing: Seam carving permits for non-uniform resizing, that means that completely different quantities can resize completely different picture components. This permits the preservation of vital particulars whereas resizing much less crucial areas.
  4. Artifact Discount: Seam carving helps cut back artifacts which will happen in conventional resizing strategies, particularly in pictures with advanced constructions or objects.

Tremendous-Decision Picture Resizing

Tremendous-resolution is a way that goals to boost the decision of a picture, producing high-frequency particulars that will not be current within the authentic picture.

  1. Upsampling: Tremendous-resolution includes growing the spatial decision of a picture by upsampling, the place finer particulars are generated between present pixels.
  2. Studying-Based mostly Approaches: Fashionable super-resolution methods typically contain deep studying approaches. Convolutional Neural Networks (CNNs) are skilled to be taught the mapping between low-resolution and high-resolution picture pairs.
  3. Single Picture Tremendous-Decision (SISR): Some methods give attention to enhancing the decision of a single picture with out counting on further high-resolution counterparts. These strategies use discovered priors to generate believable high-resolution particulars.
  4. Functions: Tremendous-resolution is especially helpful in functions the place high-quality pictures are required, equivalent to medical imaging, satellite tv for pc imagery, and surveillance.
  5. Commerce-offs: Whereas super-resolution can improve picture particulars, it’s important to notice that it can’t get better info that’s not current within the authentic low-resolution picture. The outcomes rely upon the standard of the coaching knowledge and the chosen super-resolution mannequin.

A number of libraries and instruments can be found for picture resizing. Let’s evaluate OpenCV with some widespread options:

OpenCV vs PIL/Pillow

OpenCV and PIL/Pillow are broadly used libraries for image-processing duties. Whereas OpenCV focuses extra on pc imaginative and prescient duties, PIL/Pillow supplies a broader vary of picture manipulation features. The selection between the 2 depends upon the precise necessities of your undertaking.


# PIL/Pillow for Picture Resizing
from PIL import Picture
# Load a picture from file
original_image_pillow =
# Set the specified width and top
target_width = 300
target_height = 200
# Resize the picture utilizing PIL/Pillow
resized_image_pillow = original_image_pillow.resize((target_width, target_height))
# Show the unique and resized pictures utilizing PIL/Pillow
original_image_pillow.present(title="Authentic Picture")
resized_image_pillow.present(title="Resized Picture (Pillow)")

OpenCV vs scikit-image

Scikit-image is one other widespread library for image-processing duties in Python. It supplies a complete set of picture resizing, filtering, and manipulation features. OpenCV, however, is extra specialised for pc imaginative and prescient duties. The selection between the 2 depends upon the precise wants of your undertaking.


# scikit-image for Picture Resizing
from skimage import io, rework
# Load a picture from file
original_image_skimage = io.imread(image_path)
# Set the specified width and top
target_width = 300
target_height = 200
# Resize the picture utilizing scikit-image
resized_image_skimage = rework.resize(original_image_skimage, (target_height, target_width))
# Show the unique and resized pictures utilizing scikit-image
io.title('Authentic Picture')
io.title('Resized Picture (scikit-image)')

OpenCV vs. ImageMagick

ImageMagick is a robust command-line software for picture manipulation. It supplies a variety of features for resizing, cropping, and remodeling pictures. Alternatively, OpenCV is a Python library that provides related performance and extra pc imaginative and prescient capabilities. The selection between the 2 depends upon your most popular programming language and the complexity of your undertaking.


# ImageMagick for Picture Resizing (utilizing subprocess)
import subprocess
# Set the paths
# Set the specified width and top
target_width = 300
target_height = 200
# Use ImageMagick command-line software for resizing
resize_command = f"convert {input_image_path} -resize {target_width}x{target_height} {output_image_path}", shell=True)
# Word: Make sure that ImageMagick is put in in your system for the subprocess to work.

Picture Resizing for Particular Use Circumstances

Picture resizing serves completely different functions in varied functions. Let’s discover some particular use instances:

  1. Picture Resizing for Internet Functions: In internet improvement, picture resizing is important to optimize the loading time of internet pages. By resizing pictures to the suitable dimensions, we will cut back the file dimension and enhance the general efficiency of internet functions.
  2. Picture Resizing for Laptop Imaginative and prescient Duties: In pc imaginative and prescient duties like object detection and recognition, resizing pictures to a particular dimension is usually essential. By resizing pictures to a constant dimension, we will make sure that the enter to our pc imaginative and prescient fashions stays constant and correct.
  3. Picture Resizing for Machine Studying Fashions: Machine studying fashions typically require resizing pictures to a particular dimension earlier than coaching or inference. By resizing pictures to a constant dimension, we will guarantee compatibility with our machine-learning fashions and enhance their efficiency.


Picture resizing is a basic operation in pc imaginative and prescient that enables us to regulate the size of pictures whereas sustaining their side ratio. OpenCV supplies varied methods and features for picture resizing in Python. Following the steps outlined on this article, you’ll be able to resize pictures effectively for various functions. Contemplate the challenges and select the suitable methods primarily based in your particular necessities.

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