一、概述

OpenCV(Open Source Computer Vision Library官网)是一个包含数百种计算机视觉算法的开源库。本文档描述了OpenCV 2.X API(本质是一个C++ API)。
OpenCV由模块化构成，其中包含多个共享或静态库，其核心包含以下模块

• Core functionanlity(core)核心功能：包含基本数据结构定义，包括稠密多维数组类型Mat和其他模块所需的基本函数；
• Image Processing(imgproc)图像处理：包括线性和非线性图像滤波，图像的几何变换(缩放、仿射和透视变换、基于表格的重映射)、色域转换、直方图等；
• Video Analysis(video)视频分析：包括运动估计、背景消除和目标跟踪算法的视频分析模块；
• Camera Calibration and 3D Reconstruction(calib3d)相机标定和三维重建：包含基础的多视图几何、单目和立体视觉标定、位姿估计、立体匹配和元素三维重建等算法；
• 2D Features Framework(features2d)2D特征框架：包含显著特征检测器、描述符和描述符匹配器；
• Object Detection(objdetect)目标检测：包含目标检测和预定义类别的部分实例(人脸、眼睛、杯子、人物、汽车等)；
• High-level GUI(highgui)高级GUI：提供方便调用的简单GUI接口；
• Video I/O(videoio)视频I/O：提供方便调用的视频采集和解码接口。
• …一些其他辅助模块，例如FLANN和Google单元测试封装、Python绑定等。

首先，请务必熟悉库中常见的API概念：

• cv Namespace：所有的OpenCV 类和函数均放置于cv命名空间中。因此，要在代码中调用时，请使用cv：：符或using namespace cv；指令；
• Automatic Memory Management：OpenCV自动处理所有内存；
• Automatic Allocation of the Output Data：自动根据输出函数参数分配内存；
• Saturation Arithmetics：饱和算法
• Fixed Pixel Types. Limited Use of Templates：固定像素类型，限制模板使用
• InputArray and OutputArray：输入数组和输出数组
• Error Handing：异常处理
• Multi-threading and Re-enterability：多线程和可重入性

  二、模块

  2.1 主要模块

  core. Core functionality

• Basic structures
• C structures and operations
• Operations on arrays
• Asynchronous API
• XML/YAML Persistence
• Clustering
• Utility and system functions and macros
• OpenGL interoperability
• Intel IPP Asychronous C/C++ Converters
• Optimization Algorithms
• DirectX interoperability
• Eigen support
• OpenCL support
• Intel VA-API/OpenCL(CL-VA) interoperability
• Hardware Acceleration Layer

• Parallel Processing

  imgproc. Image Processing

• Image Filtering

• Geometric Image Transformations
• Miscellaneous Image Transformations
• Drawing Functions
• Color Space Conversions
• ColorMaps in OpenCV
• Planar subdivision
• Histograms
• Structural Analysis and Shape Descriptors
• Motion Analysis and Object Tracking
• Feature Detection
• Object Detection
• Image Segmentation
• C API

• Hardware Acceleration Layer

  imgcodecs. Image file reading and writing

• C API

• Flags used for image file reading and writing
• iOS glue

• MacOS(OSX) glue

  videoio. Video I/O

• Flags for video I/O

• Additional flage for video I/O API backends
• Hardware-accelerated video decoding and encoding
• C API for video I/O
• iOS glue for video I/O
• WinRT glue for video I/O

• Query I/O API backends registry

  highgui. High-level GUI

• Flags related creating and manipulationg HighGUI windows and mouse events

• OpenGL support
• Qt New Functions
• WinRT support

• C API

  video. Video Analysis

• Motion Analysis

• Object Tracking

• C API

  calib3d. Camera Calibration and 3D Reconstruction

• Fisheye camera model

• C API

  feature2d. 2D Features Framework

• Feature Detection and Description

• Descriptor Matchers
• Drawing Function of Keypoints and Matches
• Object Categorization

• Hardware Acceleration Layer

  objdetect. Object Detection

• C API

  dnn. Deep Neural Network module

• Partial List of Implemented Layers

• Utilities for New Layers Reistration

  ml. Machine Learning

  flann. Clustering and Search in Multi-Dimensional Spaces

  photo. Computational Photography

• Inpainting

• Denoising
• HDR imaging
• Contrast Preserving Decolorization
• Seamless Cloning
• Non-Photorealistic Rendering

• C API

  stitching. Images stitching

• Features Finding and Images Matching

• Rotation Estimation
• Autocalibration
• Images Warping
• Seam Estimation
• Exposure Compensation

• Image Blenders

  gapi. Graph API

  2.2 额外模块

  alphamat. Alpha Matting

  aruco. ArUco Marker Detection

  barcode. Barcode detecting and decoding methods

  bgsegm. Improved Background-Foreground Segmentation Methods

  bioinspired. Biologically inspired vision models and derivated tools

  ccalib. Custom Calibration Pattern for 3D reconstruction

  cudaarithm. Operations on Matrices

• Core Operations on Matrices

• Per-element Operations
• Matrix Reductions

• Arithm Operations on Matrices

  cudabgsegm. Background Segmentation

  cudacodec. Video Encoding/Decoding

  cudafeatures2d. Feature Detection and Description

  cudafilters. Image Filtering

  cudaimgproc. Image Processing

• Color space processing

• Histogram Calculation
• Hough Transform

• Feature Detection

  cudalegacy. Legacy support

• NPPST Core

• NPPST Image Processing

• NPPST Signal Processing

  cudaobjdetect. Object Detection

  cudaoptflow. Optical Flow

  cudastereo. Stereo Correspondence

  cudawarping. Image Warping

  cudev. Device layer

  cvv. GUI for Interactive Visual Debugging of Computer Vision Programs

  datasets. Framework for working with different datasets

• Action Recognition

• Face Recognition
• Gesture Recognition
• Human Pose Estimation
• Image Registration
• Image Segmentation
• Multiview Stereo Matching
• Object Recognition
• Pedestrian Detection
• SLAM
• Super Resolution
• Text Recognition

• Tracking

  dnn_objdetect. DNN used for object detection

  dnn_superres. DNN used for super resolution

  dpm. Deformable Part-based Models

  face. Face Analysis

  freetype. Drawing UTF-8 strings with freetype/harfbuzz

  fuzzy. Image processing based on fuzzy mathematics

• Math with F0-transform support

• Math with F1-transform support

• Fuzzy image processing

  hdf. Hierarchical Data Format I/O routines

• Hierarchical Data Format version 5

  hfs. Hierarchical Feature Selection for Efficient Image Segmentation

  img_hash. The module brings implementations of different image hashing algorithms.

  intensity_transform. The module brings implementations of intensity transformation algorithms to adjust image contrast.

  julia. Julia bindings for OpenCV

  line_descriptor. Binary descriptors for lines extracted from an image

  mcc. Macbeth Chart module

• Color Correction Model

  optflow. Optical Flow Algorithms

  ovis. OGRE 3D Visualiser

  phase_unwrapping. Phase Unwrapping API

  plot. Plot function for Mat data

  quality. Image Quality Analysis (IQA) API

  rapid. silhouette based 3D object tracking

  reg. Image Registration

  rgbd. RGB-Depth Processing

  saliency. Saliency API

  sfm. Structure From Motion

• Conditioning

• Fundamental
• Input/Output
• Numeric
• Projection
• Robust Estimation
• Triangulation
• Reconstruction

• Simple Pipeline

  shape. Shape Distance and Matching

  stereo. Stereo Correspondance Algorithms

  structured_light. Structured Light API

  superres. Super Resolution

  surface_matching. Surface Matching

  text. Scene Text Detection and Recognition

• Scene Text Detection

• Scene Text Recognition

  tracking. Tracking API

• Tracking API implementation details

• Legacy Tracking API

  videostab. Video Stabilization

• Global Motion Estimation

• Fast Marching Method

  viz. 3D Visualizer

• Widget

  wechat_qrcode. WeChat QR code detector for detecting and parsing QR code.

• Experimental 2D Features Algorithms

• Non-free 2D Features Algorithms

• Experimental 2D Features Matching Algorithm

  xfeatures2d. Extra 2D Features Framework

• Experimental 2D Features Algorithms

• Non-free 2D Features Algorithms

• Experimental 2D Features Matching Algorithm

  ximgproc. Extended Image Processing

• Structured forests for fast edge detection

• EdgeBoxes
• Filters
• Superpixels
• Image segmentation
• Fast line detector
• EdgeDrawing
• Fourier descriptors
• Binary morphology on run-length encoded image

  xobjdetect. Extended object detection

  xphoto. Additional photo processing algorithms

  2.3 支持语言

  链接