Image Processing in Python With Pillow
A lot of applications use digital images, and with this, there is usually a need to process the images used. If you are building your application with Python and need to add image processing features to it, there are various libraries you could use. Some popular ones are OpenCV, scikit-image, Python Imaging Library and Pillow.
We won’t debate on which library is the best here, they all have their merits. This article will focus on Pillow, a library that is powerful, provides a wide array of image processing features, and is simple to use.
Pillow is a fork of the Python Imaging Library (PIL). PIL is a library that offers several standard procedures for manipulating images. It’s a powerful library, but hasn’t been updated since 2011 and doesn’t support Python 3. Pillow builds on this, adding more features and support for Python 3. It supports a range of image file formats such as PNG, JPEG, PPM, GIF, TIFF, and BMP. We’ll see how to perform various operations on images such as cropping, resizing, adding text to images, rotating, greyscaling, eTC. using this library.
Before installing Pillow, there are some prerequisites that must be satisfied. These vary for different operating systems. We won’t list the different options here, you can find the prerequisites for your particular OS in this installation guide.
After installing the prerequisite libraries, you can install Pillow with :
To follow along, you can download the images (courtesy of Unsplash) that we’ll use in the article. You can also use your own images.
All examples will assume the required images are in the same directory as the python script file being run.
A crucial class in the Python Imaging Library is the class. It is defined in the module and provides a PIL image on which manipulation operations can be carried out. An instance of this class can be created in several ways: by loading images from a file, creating images from scratch or as a result of processing other images. We’ll see all these in use.
To load an image from a file, we use the function in the module passing it the path to the image.
If successful, the above returns an object. If there was a problem opening the file, an exception will be raised.
After obtaining an object, you can now use the methods and attributes defined by the class to process and manipulate it. Let’s start by displaying the image. You can do this by calling the method on it. This displays the image on an external viewer (usually xv on Unix, and the Paint program on Windows).
You can get some details about the image using the object’s attributes.
For more on what you can do with the class, check out the documentation.
When you are done processing an image, you can save it to file with the method, passing in the name that will be used to label the image file. When saving an image, you can specify a different extension from its original and the saved image will be converted to the specified format.
The above creates an Image object loaded with the image and saves it to a new file . Pillow sees the file extension has been specified as PNG and so it converts it to PNG before saving it to file. You can provide a second argument to to explicitly specify a file format. This will do the same thing as the previous . Usually it’s unnecessary to supply this second argument as Pillow will determine the file storage format to use from the filename extension, but if you’re using non-standard extensions, then you should always specify the format this way.
To resize an image, you call the method on it, passing in a two-integer tuple argument representing the width and height of the resized image. The function doesn’t modify the used image, it instead returns another Image with the new dimensions.
The method returns an image whose width and height exactly match the passed in value. This could be what you want, but at times you might find that the images returned by this function aren’t ideal.
