cv2 imread method implementation in Python

cv2 imread method implementation in Python ( Size, Shape, Type, Length )

OpenCV is a cross-platform library that allows you to develop compute vision applications. It can do many things like image processing, video capturing e.t.c. Using it you can make projects like face detection, object detection e.t.c. OpenCV has many functions that do all these tasks efficiently. The cv2 imread() function is one of them. It allows you to read any image. In this entire tutorial, you will know its implementation.

Most of the functions are built for processing images and videos. Let’s know the picture that I am using in the upcoming examples. And it is the below.

flowers
Sample Image for using imread() method.

How to read image file using cv2 imread() method

To read the image using imread() method, you have to pass two parameters. One is the path of the image and the other is the flag, which is optional. The flag can be any one of the values from  cv2.IMREAD_COLOR,cv2.IMREAD_COLOR and  cv2.IMREAD_UNCHANGED. The flag cv2.IMREAD_COLOR is the default.

Let’s read the image using the cv2 imread() method.

import cv2
img = cv2.imread("flowers.jpg")
print(img)

Output

Printing image after reading Image File using imread() method
Printing image after reading Image File using imread() method

How to know image type in OpenCV

Now you have read the image using the cv2.imread(), let’s know the type of the image. To do so you will use the default python method type().

type(img)

In the same way, you can also know the data type of the image using the img.dtype. Run the codes given below to know the type of the image.

print("Image type:",type(img))
print("Image Data Type: ",img.dtype)

Output

Type and dtype of the image file
Type and dtype of the image file

You can see all the pixel values of the image are of a NumPy array type. And the maximum values of each pixel can be from 0 to 256 (2**8).

Know the shape of the image in OpenCV

The shape tells the dimensions of the image file you read. In OpenCV, you have to the img. shape to find the dimensions.

print(img.shape)

Output

Shape of the image in opencv python
The shape of the image in OpenCV python

Here 425 is the number of columns, 640 is the number of rows and 3 is the number of channels. My image is colorful, that’s why the channel will be 3. For the gray image, it is 1.

Find the size of the image in OpenCV python

The above shape tells you the dimension of the image. If you use img.size then it will multiply all the values (425*640*3) you get in the img.shape.

print(img.size)

Output

816000

Get length of the image in python using cv2 imread

You can also know the dimensions of the image file using len() method. For example, to know the total rows (height) you will use the len(img). In the same to know the total columns(width), use len(img[0]). Lastly, to know the number of channels use len(img[0][0]).

Run the following lines of code and see the output.

print("Rows or Height:",len(img))
print("Columns or Width:",len(img[0]))
print("Number of channels:",len(img[0][0]))

Output

Getting the size of the image using the len() function
Getting the size of the image using the len() function

Conclusion

Reading the image file is a must for further processing of the image. These are the examples that will clear your understanding of how to read image file in python using the cv2 imread() method. Even you are finding difficulties in it then you can contact us for more help.

Source:

OpenCV python Offical Documentation

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