OpenCV - OpenCV is the world's biggest computer vision library
Amazon Rekognition - Add Amazon's advanced image analysis to your applications.
Microsoft Computer Vision API - Extract rich information from images and analyze content with Computer Vision, an Azure Cognitive Service.
Clarifai - The World's AI
Google Vision AI - Cloud Vision API provides a comprehensive set of capabilities including object detection, ocr, explicit content, face, logo, and landmark detection.
Trueface Visionbox - Trueface Visionbox is a platform that offers vision solutions to the world by converting the camera into actionable information, and users can easily learn about anything through it.