In this article, we will cover the basics of image manipulation in OpenCV and how to resize an image in Python, its cropping, and rotating techniques.

• Change System Photo Library On Mac
• Change System Photo Library Mac
• Change System Photo Library On Mac
• Change System Photo Library

We will use Python version 3.6.0, OpenCV version 3.2.0. It is an assumption that you have Python installed on your machine and already know the basics of Python programming. Please read the article if you need a tutorial on how to install OpenCV for Python.

Before we go any further, let’s remember about Core Operations in OpenCV for image processing. This operation consists of reading the image, displaying the image, and saving the image.

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For these operations, we need to use the Pillow Library first. If you have not downloaded Pillow to your system before, you can use the following code:

First, we need to import Pillow Libraries:

To use shorter file names in our system, we should prefer OS and Glob modules. It is used to change, save and open images with PIL to PIL image or different optimization options.

OUTPUT>>>

OUTPUT>>>

Reading Images

To read images in OpenCV, use a function cv2.imread()where the first parameter is the image file name complete with its extension. As an example :

Cv2 function. Whiskey ( 0 ) is to keep the window displaying the image. While the cv2 function. destroyAllWindows ( ) is to close other windows that are currently open.

Displaying an Image

Displaying an image in OpenCV using a function cv2.imshow()where the first parameter is the window name to display the image and the second parameter is the image itself.

Writing / Saving Images

To write / save images in OpenCV using a function cv2.imwrite()where the first parameter is the name of the new file that we will save and the second parameter is the source of the image itself.

For details on OpenCV Core Image Operations, please read the OpenCV documentation.

Now we can go back to the original topic of basic image manipulation in OpenCV and Python. As explained earlier in this article, we will learn how to apply resizing, cropping, and rotating techniques to images.
Let’s first try reading our image source and displaying it with the functions previously described.

Henceforth, we will use the image above in this paper. Run the print command ( img . Shape ) to display the dimensions of our source image. The command will output (680, 850, 2) where 680 is the width, and 850 is the height in pixel size, while 2 is the image channel (RGB), or it means that the image has 680 rows and 850 columns.

Please note that if we read the image in grayscale form, the output will only produce rows and columns. So the img command . shape can also be applied to see if the image is grayscale or color image.

Image Resizing OpenCV

Earlier we got the width of our image with the img function . shape that is 850 pixels. Let’s resize the image to be 2 times smaller.

#Specifying Image Size and Resizing

#Displaying Images

OpenCV Image Cropping

Keep in mind that every image we read with the cv2.imshow () function returns data in the form of an array.

Cropping application to OpenCV is very easy; we need to determine where the coordinates of the image to be cropped. First, we determine the initial x coordinate and final x, then determine the initial y coordinate and end y coordinates of the image that has been said to be read earlier.

From the command above, the crop results from our initial image will appear following the coordinates we specified earlier.

Image Rotating OpenCV

Changing the rotation isn’t that difficult either. First we have to determine the center point of rotation which we can determine from the width and height of the image, then determine the degree of rotation of the image and the dimensions of the image output.

Next is to apply the rotation settings that we have defined on the image we read earlier and display the image.

Quick Recap on Comands

Time needed: 1 hour.

Change System Photo Library On Mac

Here’s a list that will help you refresh you memory.

1. Reading Images

   cv2.imread()

2. Displaying an Image

   cv2.imshow()

3. Writing / Saving Images

   cv2.imwrite()

4. Image Resizing OpenCV

   cv2.resize()

5. OpenCV Image Cropping

   cv2.imshow()

6. Image Rotating OpenCV

   cv2.warpAffine()

   You can also like this post: Photo Editing Software Options

FAQs About How to Resize an Image in Python

You can use the Python version 3.6.0 and the OpenCV version 3.2.0.

It would be best if you already know the basics of Python programming.

Change System Photo Library Mac

Yes, you should check the Core Operations in OpenCV for image processing.

You can write/save images in OpenCV using a function cv2.imwrite()where the first parameter is the name of the new file that you must save. The second parameter is the source of the image itself.

If you read an image in grayscale form, the output will only produce rows and columns.

Change System Photo Library On Mac

How to Resize an Image in Python in Short

These are the basics of Image Manipulation with OpenCV and the ways you can resize an image in Python. You can easily make arrangements with the image sizes in Python. Speaking of image manipulation, you better check out how to center a div element in CSS, as well.

Change System Photo Library