What is winStride?
winStride (optional) The winStride parameter is a 2-tuple that dictates the “step size” in both the x and y location of the sliding window. Both winStride and scale are extremely important parameters that need to be set properly.
What is detect multi scale?
Higher value results in less detections but with higher quality. The idea behind this parameter is that the detector will run on a multiple scale style and at the same time following sliding window strategy. After this step, it will give you multiple responses even for a single face region.
What is scale factor in detectMultiScale?
scaleFactor – Parameter specifying how much the image size is reduced at each image scale. Basically the scale factor is used to create your scale pyramid.
What is hog OpenCV?
The HOG feature descriptor counts the occurrences of gradient orientation in localized portions of an image. Implementing HOG using tools like OpenCV is extremely simple. It’s just a few lines of code since we have a predefined function called hog in the skimage.
What does faceCascade detectMultiScale return?
faceCascade. detectMultiScale() returns a list of rectangles so it does not contain the images of the detected faces and you cannot reconstruct the faces purely from that list.
What is cascade classifier Opencv?
This is basically a machine learning based approach where a cascade function is trained from a lot of images both positive and negative. Based on the training it is then used to detect the objects in the other images.
What is cascade classifier in OpenCV?
It is a machine learning based approach where a cascade function is trained from a lot of positive and negative images. It is then used to detect objects in other images. Initially, the algorithm needs a lot of positive images (images of faces) and negative images (images without faces) to train the classifier.
What is detectMultiScale OpenCV?
detectMultiScale (InputArray image, std::vector< Rect > &objects, double scaleFactor=1.1, int minNeighbors=3, int flags=0, Size minSize=Size(), Size maxSize=Size()) Detects objects of different sizes in the input image. The detected objects are returned as a list of rectangles.
What is cascade classifier in Opencv?
What is SVM HOG?
Histogram of oriented gradients (HOG) is used for feature extraction in the human detection process, whilst linear support vector machines (SVM) are used for human classification. A set of tests is conducted to find the classifiers which optimize recall in the detection of persons in visible video sequences.
What is sift and HOG?
HOG is another way to describe an image with a gradient vector. I think Dense SIFT is a special case for HOG. In HoG, if we set the bin size to 8, for each window there are 4 blocks, for each block, there are 4 cells and the block stride is the same as the block size, we can still get a 128 dim vector for this window.
What is OpenCV for face detection?
OpenCV is a video and image processing library and it is used for image and video analysis, like facial detection, license plate reading, photo editing, advanced robotic vision, and many more.
Where can I find documentation for OpenCV hogdescriptor?
Almost none documentation can be found for OpenCV HOGDescriptor, other than the source cpp code. Scikit-image has a good example page on extracting and illustrating HOG feature. It provides an alternative to explore HOG. It is documented here. However, there is one thing to point out about scikit-image’s hog implementation.
How to detect pedestrians in images and video using OpenCV?
In this tutorial, we will write a program to detect pedestrians in a photo and a video using a technique called the Histogram of Oriented Gradients (HOG). We will use the OpenCV computer vision library, which has a built-in pedestrian detection method that is based on the original research paper on HOG .
How does winstride work in computer vision and deep learning?
If you work with computer vision and deep learning, then you may be well aware of the stride that is used in convolution kernels. This winStride also works in pretty much the same way. It defines a step size for the detector window to move in the horizontal and vertical direction.
How is a person detector trained in OpenCV?
OpenCV already has an implementation of a person detector model. The OpenCV module name is HOGDescriptor_getDefaultPeopleDetector (). It is trained using the Linear SVM machine learning classifier, just as we discussed in the last tutorial. Let’s learn about the OpenCV Person Detector in a little bit more detail.