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How to access image properties in OpenCV using Python?
An image in OpenCV is a NumPy array. We can access the image properties using the attributes of the numpy array. We access the following image properties for the input image img −
Image Type − data structure of the mage. Image in OpenCV is numpy.ndarray. We can access it as type(img).
Image Shape − It is the shape in [H, W, C] format, where H, W, and C are the height, width and number of channels of the image respectively. We can access it as img.shape.
Image Size − It is the total number of pixels in an image. Also it is the total number of elements in the array. We can access it as img.size.
Data type − its the dtype of elements of the image array. We can access it as img.dtype.
Dimension − the dimension of image. A color image has 3 dimensions (height, width and channels) whereas a gray image has 2 dimensions (only height and width). We can access it as img.ndim.
Pixel values − the pixel values are unsigned integers in range 0 and 255. We can directly access these values as print(img).
Let's have a look at some Python programs to access the properties of an image.
Input Image
We will use this image as the input file in the following examples.
Example 1
In this program, we will access the image properties of the given color image.
import cv2 # read the input image img = cv2.imread('cat.jpg') # image properties print("Type:",type(img)) print("Shape of Image:", img.shape) print('Total Number of pixels:', img.size) print("Image data type:", img.dtype) # print("Pixel Values:\n", img) print("Dimension:", img.ndim)
Output
When you run this program, it will produce the following output −
Type: <class 'numpy.ndarray'=""> Shape of Image: (700, 700, 3) Total Number of pixels: 1470000 Image data type: uint8 Dimension: 3
Let’s look at another example.
Example 2
In this program, we will access the image properties of a gray mage.
import cv2 # read the input image img = cv2.imread('cat.jpg', 0) # image properties print("Type:",type(img)) print("Shape of Image:", img.shape) print('Total Number of pixels:', img.size) print("Image data type:", img.dtype) print("Pixel Values:\n", img) print("Dimension:", img.ndim)
Output
When you run the above python program, it will produce the following output −
Type: <class 'numpy.ndarray'> Shape of Image: (700, 700) Total Number of pixels: 490000 Image data type: uint8 Pixel Values: [[ 92 92 92 ... 90 90 90] [ 92 92 92 ... 90 90 90] [ 92 92 92 ... 90 90 90] ... [125 125 125 ... 122 122 121] [126 126 126 ... 122 122 122] [126 126 126 ... 123 123 122]] Dimension: 2
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