The contours of the objects in an image are very helpful to compute the area and perimeter of the image. A contour of an image is a curve joining all the continuous points along the boundary, having the same color or intensity. Contours are used for shape analysis and object ... Read More

The solidity of an object is computed as the ratio of contour area to its convex hull area. So to compute the solidity, we first have to find the contour area and convex hull area. The contour area of an object can be found using cv2.contourArea() function. Equivalent Diameter is ... Read More

The extent of an object is computed as the ratio of contour area to its bounding rectangle area. So, to compute the extent, we first have to find the contour area and bounding rectangle area. The contour area of an object can be found using cv2.contourArea() function. Syntax The extent ... Read More

The aspect ratio of an object is computed as the ratio between the width and height of the bounding rectangle of the object. So, to compute the aspect ratio, we first have to find the bounding rectangle of the object. Bounding rectangle of an object can be found using cv2.boundingRect() ... Read More

We can fit an ellipse to an object using the function cv2.fitEllipse(). The ellipse is inscribed in a rotated rectangle. The rotated rectangle is a bounding rectangle with minimum area enclosing the object. Syntax The syntax used for this function is − ellipse = cv2.fitEllipse(cnt) Where, "cnt" is the ... Read More

To add a watermark to an image, we will use the cv2.addWeighted() function from OpenCV. You can use the following steps to create a watermark on an input image − Import the required library. In all the following Python examples, the required Python library is OpenCV. Make sure you have ... Read More

A minimum enclosing circle (circumcircle) of an object is a circle which completely covers the object with minimum area. We can find the minimum enclosing circle of an object using the function cv2.minEnclosingCircle(). Syntax The syntax of this function is − (x, y), radius = cv2.minEnclosingCircle(cnt) Where, "cnt" are ... Read More

A Convex Hull looks similar to contour approximation, but it is not exactly a contour approximation. A convex hull is a convex curve around an object. A convex curve is always bulged out, or at-least flat. A convex hull finds the convexity defects and corrects them. Syntax To find the ... Read More

The Hu-Moments can be found using the cv2.HuMoments() function. It returns seven moments invariant to translation, rotation and scale. Seventh moment is skew-invariant. To compute the Hu-Moments, we need to first find the image. The image moments are computed for an object using the contour of the object. So, first, ... Read More

To draw a filled ellipse on an image, we use the cv2.ellipse() method. This method accepts different arguments to draw different types of ellipses. Syntax cv2.ellipse(img, center, axes, angle, start_angle, end_angle, color, thickness) Parameters img − The input image on which the ellipse is to be drawn. center ... Read More