Reading an image in OpenCV using Python
Prerequisite: Basics of OpenCV
In this article, we’ll try to open an image by using OpenCV (Open Source Computer Vision). To use the OpenCV library in python, we need to install these libraries as a prerequisite:
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- Numpy Library (Necessary, because OpenCV uses it in the background).
- OpenCV python
To install these libraries, we need to run these pip commands in cmd:
pip install opencv-python pip install numpy pip install matplotlib
To read the images cv2.imread() method is used. This method loads an image from the specified file. If the image cannot be read (because of missing file, improper permissions, unsupported or invalid format) then this method returns an empty matrix.
Syntax: cv2.imread(path, flag)
path: A string representing the path of the image to be read.
flag: It specifies the way in which image should be read. It’s default value is cv2.IMREAD_COLOR
Return Value: This method returns an image that is loaded from the specified file.
Note: The image should be in the working directory or a full path of image should be given.
All three types of flags are described below:
cv2.IMREAD_COLOR: It specifies to load a color image. Any transparency of image will be neglected. It is the default flag. Alternatively, we can pass integer value 1 for this flag.
cv2.IMREAD_GRAYSCALE: It specifies to load an image in grayscale mode. Alternatively, we can pass integer value 0 for this flag.
cv2.IMREAD_UNCHANGED: It specifies to load an image as such including alpha channel. Alternatively, we can pass integer value -1 for this flag.
Below codes are implementations to read images and display images on the screen using OpenCV and matplotlib libraries functions.
Example #1 (Using OpenCV) :
Example #2: Opening in grascale mode