OpenCV - OpenCV is the world's biggest computer vision library
Microsoft Computer Vision API - Extract rich information from images and analyze content with Computer Vision, an Azure Cognitive Service.
Clarifai - The World's AI
Amazon Rekognition - Add Amazon's advanced image analysis to your applications.
Google Vision AI - Cloud Vision API provides a comprehensive set of capabilities including object detection, ocr, explicit content, face, logo, and landmark detection.
PCV - PCV is an open source Python module for computer vision.