Draw arrow segment in OpenCV

Drawing an arrow segment in OpenCV can be accomplished using the arrowedLine() function. The function allows you to define the starting and ending points of the arrow, its color, thickness, and other properties.

Let's go through a simple tutorial on how to draw an arrow segment on an image using OpenCV.

Steps to Draw an Arrow Segment using OpenCV:

1. Setup:

First, ensure OpenCV is installed:

pip install opencv-python

Import necessary libraries:

import cv2
import numpy as np

2. Load or Create an Image:

For this tutorial, we'll create a blank image, but you can also load your own:

# Create a blank image (white background)
image = np.ones((500, 500, 3), np.uint8) * 255

Or load an existing image:

# image = cv2.imread('path_to_image.jpg')

3. Draw an Arrow Segment:

You can use cv2.arrowedLine() to draw an arrow. Here's the basic syntax:

cv2.arrowedLine(img, start_point, end_point, color[, thickness[, line_type[, shift[, tipLength]]]])

img: The image on which the arrow is drawn.
start_point: The starting point of the arrow segment.
end_point: The ending point (tip) of the arrow.
color: Arrow color.
thickness (optional): Line thickness.
line_type (optional): Line type (like 8-connected, anti-aliased line etc.)
shift (optional): Number of fractional bits in the point coordinates.
tipLength (optional): The length of the arrow tip in relation to the arrow length.

Here's an example:

start_point = (50, 250)
end_point = (450, 250)
color = (0, 0, 255)  # Red color in BGR
thickness = 2
tip_length = 0.2  # 20% of the arrow length

cv2.arrowedLine(image, start_point, end_point, color, thickness, tipLength=tip_length)

4. Display the Image:

cv2.imshow('Arrow Segment', image)
cv2.waitKey(0)
cv2.destroyAllWindows()

When you run the code, you'll see a blank window with a red arrow drawn across its width. You can adjust the starting and ending points, color, thickness, and tip length as needed.

That's it! Using the arrowedLine() function, you can quickly draw arrows on images in OpenCV, making it useful for annotating images, especially in computer vision tasks where you might want to indicate direction or movement.

Drawing Arrow Segments in OpenCV:

Description: Introduction to basic arrow drawing in OpenCV.

Code:

import cv2
import numpy as np

# Create a black image
img = np.zeros((300, 400, 3), dtype=np.uint8)

# Define arrow starting and ending points
start_point = (50, 150)
end_point = (350, 150)

# Draw arrow segment on the image
cv2.arrowedLine(img, start_point, end_point, (0, 255, 0), 2)

# Display the image
cv2.imshow('Arrow Segment', img)
cv2.waitKey(0)
cv2.destroyAllWindows()