Create rectangle in opencv python
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View Discussion Show Improve Article Save Article View Discussion Improve Article Save Article OpenCV-Python is a library of Python bindings designed to solve computer vision problems.
Image used for all the below examples:  Example #1:
Output: Example #2: Using thickness of -1 px to fill the rectangle by black color.
Output: Goal
CodeIn all the above functions, you will see some common arguments as given below:
Drawing LineTo draw a line, you need to pass starting and ending coordinates of line. We will create a black image and draw a blue line on it from top-left to bottom-right corners. import numpy as np import cv2 as cv img = np.zeros((512,512,3), np.uint8) cv.line(img,(0,0),(511,511),(255,0,0),5) Drawing RectangleTo draw a rectangle, you need top-left corner and bottom-right corner of rectangle. This time we will draw a green rectangle at the top-right corner of image. Drawing CircleTo draw a circle, you need its center coordinates and radius. We will draw a circle inside the rectangle drawn above. Drawing EllipseTo draw the ellipse, we need to pass several arguments. One argument is the center location (x,y). Next argument is axes lengths (major axis length, minor axis length). angle is the angle of rotation of ellipse in anti-clockwise direction. startAngle and endAngle denotes the starting and ending of ellipse arc measured in clockwise direction from major axis. i.e. giving values 0 and 360 gives the full ellipse. For more details, check the documentation of cv.ellipse(). Below example draws a half ellipse at the center of the image. Drawing PolygonTo draw a polygon, first you need coordinates of vertices. Make those points into an array of shape ROWSx1x2 where ROWS are number of vertices and it should be of type int32. Here we draw a small polygon of with four vertices in yellow color. pts = np.array([[10,5],[20,30],[70,20],[50,10]], np.int32) pts = pts.reshape((-1,1,2)) NoteIf third argument is False, you will get a polylines joining all the points, not a closed shape. cv.polylines() can be used to draw multiple lines. Just create a list of all the lines you want to draw and pass it to the function. All lines will be drawn individually. It is a much better and faster way to draw a group of lines than calling cv.line() for each line.Adding Text to Images:To put texts in images, you need specify following things.
We will write OpenCV on our image in white color. font = cv.FONT_HERSHEY_SIMPLEX cv.putText(img,'OpenCV',(10,500), font, 4,(255,255,255),2,cv.LINE_AA) ResultSo it is time to see the final result of our drawing. As you studied in previous articles, display the image to see it. image Additional Resources
Exercises
How do you make a rectangle in OpenCV?In this program, we will draw a rectangle using the OpenCV function rectangle(). This function takes some parameters like starting coordinates, ending coordinates, color and thickness and the image itself.
How do you make a rectangle in Python?We can create a simple rectangle by defining a function that takes in two integers representing side length and side height. Then we can loop four times, using the forward() function to create a side representing either the length or height, then rotating the cursor 90 degrees with the right() function.
How do I create a multiple rectangle in OpenCV Python?Function used:. Syntax: cv2.imread(path_of_image, flag). Syntax: cv2.rectangle(image, starting_coordinate, ending_coordinate, color, thickness). Syntax: cv2.imshow(window_name, image). How do you draw shapes in OpenCV?Some of the drawing functions are :. line() : Used to draw line on an image.. rectangle() : Used to draw rectangle on an image.. circle() : Used to draw circle on an image.. putText() : Used to write text on image.. |
