5 Useful Image Manipulation Techniques Using Python OpenCV by Yong Cui

• February 10, 2022
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The first for IOErrors deals with invalid filenames and the like while the second for ValueErrors deals with situations where the save method cannot deduce the format from the filename extension. It is very straightforward but I will describe the various functions further down. During this time the API and models will evolve based on your feedback. To ensure all users can prototype comfortably, the default rate limit is 50 images per minute.

If you create imgplot here in one cell, you cannot call set_cmap() on it in a later cell and expect the earlier plot to change. Make sure that you enter these commands together in one cell. You create an array of size 600×600 containing zeros everywhere. Next, you set the value of a set of pixels at the center of the array to 255. You achieve thresholding by calling .point() to convert each pixel in the grayscale image into either 255 or 0.

Now, with a luminosity image, the default colormap , is applied. With IPython started, we now need to connect to a GUI event loop. To connect to a GUI loop, execute the %matplotlib magic at your IPython prompt. There’s more detail on exactly what this does at IPython’s documentation on GUI event loops. Now that you’ve installed NumPy, you’re ready to use Pillow and NumPy to spot the difference between two images. The watermark has a rectangular outline, which is a result of the contour filter that you used earlier.

image-manipulation

While the ret is the Boolean telling that function is run successfully or not and the mask is the final output of the function i.e. the processed image. For demonstration purposes, I overlaid the resized images onto the solid background images that we created in the previous section. If you recall, the resized images have the widths of 100, 200, and 400.

Some of these libraries are faster and more powerful than Pillow. NumPy’s array operations provide a powerful set of tools for manipulating images. Since images are essentially arrays of pixel values, NumPy can be used to perform various operations on them, such as scaling, cropping, rotating, and flipping. The main library that we will use for image manipulation is called PIL, which is the image processing library. PIL will be installed as ‘pillow’, don’t get confused, they are the same thing.

Holy Python

The for loop pastes the images that you input when you call the function into the final display. The function returns the final Image object containing all the images side by side. The overall size of the display is calculated from the size of the images and the number of images used. You then create a new Image object with the same mode as the original images and with the size of the overal display. The format of an image shows what type of image you’re dealing with. You call the open() function to read the image from the file and .load() to read the image into memory so that the file can now be closed.

A virtual environment is essentially a container that houses a Python and pip installation. A few solutions exist for creating Python virtual environments. One of them is a built-in module called venv which enables you to create and manage system-wide virtual environments.

Adding a Watermark

Pycairo is a set of Python bindings for the Cairo graphics library. Vector graphics are interesting because they don’t lose clarity when resized or transformed. For a complete list of functions provided by the scipy.ndimage package, refer to the documentation. The package is imported as skimage, and most functions are found within the submodules. These Python libraries provide an easy and intuitive way to transform images and make sense of the underlying data. In larger image you will notice that still being of the same size of the original image its little blurry because its being converted from smaller image to larger image directly.

The image manipulation of the thumbnail will be smaller than or equal to the size that you set. You can place this image file in the project folder that you’re working in. When you read an image using Pillow, the image is stored in an object of type Image.

First of all, congratulate yourself that you have made up to this mini project after reading all the image manipulation functions above. So in this mini project of Python OpenCV we are going to learn some new concepts of loops and functions. If you are familiar with programming, you must have a broader idea of what the function and loops are. However, in python the basic concept of loops and functions remains the same but the method to define them changes a little. It’s also important to know the data type of the numpy array.

Values greater than 1 increase sharpness, while values less than 1 decrease sharpness or increase blur. This is the image sharpened (I should say “over-sharpened”) to 2.0. Similar to the edits endpoint, the input image must be a square PNG image less than 4MB in size. Each image can be returned as either a URL or Base64 data, using the response_format parameter. 2D raster & vector editor that melds traditional layers & tools with a modern node-based, fully non-destructive procedural workflow. Treating your image as a large array is exactly what I am suggesting.

Useful Image Manipulation Techniques Using Python OpenCV

Firstly, the image is converted into grayscale so the opencv can process it easily and then a Gaussian blur is applied to the gray scale image so as to reduce the noise. Photo by Dom J from PexelsIn this post, I will show you how to edit an image using Python. The process of editing an image is called image manipulation. You might be wondering why you need to do some touches on your images before using them in your projects. There are many reasons for this, but a couple of main reasons can be listed as saving storage space, improving the quality of training, and faster running time. The manipulation techniques that will be covered in this post are image resizing, image brightness, and lastly converting the image color to grayscale.

• SimpleITK is a simplified layer built on top of ITK, intended to facilitate its use in rapid prototyping, education and interpreted languages.
• The white squares represent pixels in the image that have a value of 0.
• The animation below visualizes a rigid CT/MR registration process created with SimpleITK and Python.
• Especially, when training the machine to learn a specific object in an image, greyscale is one of the most commonly used technique to start with.
• #non edges wheareas any value above 120 are considered as edges.

In Listing 1, the dimensions of the image were kept consistent. It is possible to resize the width separate from the height. The following shows the same listing, but this time the resizing tuple set to . ITK or Insight Segmentation and Registration Toolkit is an open-source, cross-platform system that provides developers with an extensive suite of software tools for image analysis. SimpleITK is a simplified layer built on top of ITK, intended to facilitate its use in rapid prototyping, education and interpreted languages.

Project Overview

If you do not have an installation of Python 3.9 on your system, a prompt will ask if you would like to install it. In this case, input y and press Enter to continue the installation. A directory containing your new virtual environment is created before you regain control of the terminal. Specify packages along with their version number in a Pipfile to determine a project’s dependencies. We then talk more about the program’s structure and adopted coding conventions in order to improve readability, prevent duplication, and maintain performance. Check the below code to rotate an image by 90 degrees in an anticlockwise direction.

For demonstration purposes, I created three images with the colors blue, green, and red with a size of 500 by 500. Sometimes, we need to add a background to an existing image for formatting purposes. For instance, by padding a solid color as margins, we can make many images of different sizes become the same shape. Sometimes you want to enhance the contrast in your image, or expand the contrast in a particular region while sacrificing the detail in colors that don’t vary much, or don’t matter.

Leverage the OpenCV-Python library to get creative with images

https://forexhero.info/ is a free library for the Python programming language that adds support for opening, manipulating and saving many different image file formats. However, its development has stagnated, with its last release in 2009. Fortunately, we have Pillow, an actively-developed fork of PIL which is easier to install, runs on all major operating systems and supports Python 3.

In addition to detailing how to create project-level virtual environments with Python, this article walked through the usage of our image manipulation tool. The difference between positional arguments and optional arguments was also discussed. You’ve learned how to crop and rotate images, resize them, and extract color bands from color images. However, none of the actions that you’ve taken so far have made any changes to the content of the image. In this section, you’ll learn about image processing features in the Python Pillow library. NumPy contains a matrix and multi-dimensional arrays as data structures.

If properties are output for each image — their filename, size in pixels, format, and bands — the image manipulation tool is working correctly on your system. This file is read by pipenv to create and configure a virtual environment. Important information such as the project’s Python version and package dependencies are specified here. We will go over the project’s structure, it’s source files, and how to set up a virtual environment in the next section. Python allows development projects to be approached in a goal-orientated way.

We then call the image’s copy method which (obviously!) returns a copy. It isn’t strictly necessary to create a copy — we could just call save on the original image with the new filename but I have used a copy here just to demonstrate the method. If you open the folder containg the source code and image file you will find a copy of the latter has been created.

It takes median of all pixels under the kernel area and central element is replaced with this median value. Although it’s commented out, the above code also includes a dictionary comprehension showing you how to create the same dictionary without using the for loop. Most often, the “interesting” part of the image is around the peak, and you can get extra contrast by clipping the regions above and/or below the peak. In our histogram, it looks like there’s not much useful information in the high end . Let’s adjust the upper limit, so that we effectively “zoom in on” part of the histogram.

• The image generations endpoint allows you to create an original image given a text prompt.
• We will do the most commonly used three manipulation techniques.
• #any gradient larger than threshold 2 is considered to be an edge.
• The GraphicsMagick image processing system is sometimes called the Swiss Army Knife of image processing.

We’re effectively discarding pixels, only keeping a select few. Now when we plot it, that data gets blown up to the size on your screen. The old pixels aren’t there anymore, and the computer has to draw in pixels to fill that space.

I hope including the installation and some practical application areas of those libraries can shift the article from good to great. Scikit-image is an open source Python package that works with NumPy arrays. It implements algorithms and utilities for use in research, education, and industry applications.

Also showing the image will be more convenient since you won’t need to take any additional steps. In Jupyter you will need to import image displaying libraries from IPython to do this. This article moved a little deeper into manipulating images with Python. Once again, with just a few lines of Python code you’ve seen how to resize, crop, and rotate images. This method allows you to rotate an image based on an angle measured in degrees and going in a counterclockwise direction. You should note that the thumbnail() method replaces the information stored in the existing image file.

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