Image classification and image localization are recognition of one object in an image.

Object detection is recognition of multi objects in an image.

Single Object Detection vs. Multi-object Detection in Computer Vision


1- Train data as we do for binary image classification.

2- Use sliding window detection.

Object Detection Steps in Computer Vision

Landmark detection is a fundamental building block of computer vision applications such as face recognition, pose recognition, emotion recognition, head recognition to put the crown on it, and many more in augmented reality.

Landmark Detection in Computer Vision

There are a few different algorithms for object detection and they can be split into two groups:

1. Algorithms based on classification. They are implemented in two stages. First, they select regions of interest in an image. Second, they classify these regions using convolutional neural networks. This solution can be slow because we have to run predictions for every selected region. A widely known example of this type of algorithm is the Region-based convolutional neural network (RCNN) and its cousins Fast-RCNN, Faster-RCNN and the latest addition to the family: Mask-RCNN. Another example is RetinaNet.

2. Algorithms based on regression – instead of selecting interesting parts of an image, they predict classes and bounding boxes for the whole image in one run of the algorithm. The two best known examples from this group are the YOLO (You Only Look Once) family algorithms and SSD (Single Shot Multibox Detector). They are commonly used for  real-time object detection as, in general, they trade a bit of accuracy for large improvements in speed.

Two Main Groups of Object Detection Algorithms

In this task, there are multiple objects in an image. The computer should detect objects classes and their locations.



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1- Image classification

2- Image localization

3- Object detection

4- Neural style transfer

Types of Computer Vision Problems

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Computer task is to predict the binary label of an image. 

For example, is this an image of cat or not (y=0 or y=1)

Image Recognition (Classification) in Computer Vision

Object Detection in Computer Vision

Neural style transfer generates a new image by combining the content of one image with the style of another image. 

Neural Style Transfer in Computer Vision

In this task, the computer should detect the location of the object as well and draw a bounding box around it.

Image Localization in Computer Vision

In autonomous applications such as robotics or vehicles using a camera to track where the camera are is in space can be a good localization estimate. The idea is to analyze sequential frames in a video and compare the movement of certain features in the image between them. Once the correlations are found either a Kalman filter or a 3D mapping can be found depending on the type of data available. Visual odometry can be a highly accurate measure of position but it's often used in sync with other localization and mapping techniques.


Visual Odometry

Camera's are a projection of the 3D world onto 2D a image but once you have the image how can you go back to 3D? This problem is know as reconstructing a 3D image and the most popular method is using stereo vision which is acquiring multiple angles of similar images. By aligning similar features in each image in 2D, 3D geometric information can be extracted in the form of depth maps.

3D Reconstruction

Facial landmarks are used to localize eyes, nose, mouth, jaw, eyebrows, and the face as a whole. They are an important input to many computer vision problems such as facial recognition, driver attention tracking, gaze tracking, etc. The most accurate methods are generally using neural networks trained on datasets such as 300-W, AFLW, WFLW, etc.

Facial Landmark Detection

Optical Flow is the tracking of the motion of objects between two consecutive frames of a video. It relies on pixel intensities between frames being similar and neighboring pixels having similar motion. This allows it to be a fast implementation and useful for applications such as structure from motion, video stabilization, and video compression.

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