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

To detect a triangle in an image, we first detect all the contours in the image. Then we loop over all the contours. Find the approximate contour for each of the contours. If the number of vertex points in the approximate contour is 3, then draw the contour and set ... Read More

Color images (RGB) have three channels: red, blue and green. The image is represented as a 3-dimensional numpy array. The pixel values of an image are stored using 8-bit unsigned integers (uint8) in the range "0 to 255". The bitwise XOR operation on two images is performed on the binary ... Read More

The function cv2.isContourConvex() is used to check whether a curve (contour) is convex or not. A contour of an object in the 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 detection and ... Read More

Image Moments are very important to compute the features like center of mass of an object, area of an object, etc., in a given image. Image moments are computed for an object using the contour of the object. So first, we detect the contour of the object, then apply cv2.moments(cnt) ... Read More

We use cv2.matchShapes() function to match two image shapes. This function returns a metric showing the similarity between the image shapes. This function uses Hu-Moments to calculate the metric value. Lower the metric value, higher the similarity between the image shapes. In the following examples, we will match the shapes ... Read More

We can form the Laplacian Pyramids from the Gaussian Pyramids. OpenCV does not provide any specific function to construct Laplacian Pyramids. In Laplacian pyramid, images look like edge images only. Laplacian Pyramids are used in image compression as well as in image enhancement. A level in the Laplacian Pyramid is ... Read More

In many cases, we need to work with different resolutions and sizes of the same image. In the concept of image pyramid, we find images with different resolutions and sizes of the original image. The Gaussian pyramid is a type of image pyramid. To find a Gaussian pyramid, OpenCV provides ... Read More

Using the Scharr operator, we can compute image gradients in horizontal as well as vertical direction using first order derivatives. The gradients are computed for a grayscale image. You can apply Scharr operation on an image using the method cv2.scharr(). Syntax The following syntax is used to compute the image ... Read More

To draw polylines on an image, we use the method cv2.polylines(). We can draw open or closed polylines on the image. The first and last points are not connected while drawing an open polyline. Syntax The syntax of cv2.polylines() is as follows − cv2.polylines(src, [pts], isClosed, color, thickness) Parameters ... Read More