OpenCV2.4.3参考手册：核心功能与图像处理

OpenCV2.4.3

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"OpenCV2.4.3文档" OpenCV（开源计算机视觉库）是计算机视觉和机器学习领域的一个强大工具，版本2.4.3提供了丰富的功能和API，适用于图像处理、视频分析以及高级图形用户界面。该文档详细介绍了OpenCV的核心概念和模块，以下是一些关键知识点的概述： 1. **Introduction** - OpenCV的设计目标是提供一个跨平台的库，用于实时的计算机视觉应用。API的概念涵盖了核心函数、图像处理、高级GUI和媒体I/O等多个方面。 2. **core. The Core Functionality** - 这一部分介绍了OpenCV的基本结构，包括基本的数据类型如Mat（用于存储多维数组，常用于图像数据），以及C语言结构体和操作。动态结构如Ptr和Vector<T>支持内存管理，而数组操作则提供了对图像数据的高效处理。 3. **imgproc. Image Processing** - 图像处理模块包含各种过滤器（如平滑滤波、边缘检测），几何变换（如旋转、缩放、仿射变换），以及其他图像转换（颜色空间转换、直方图均衡化）。它还涉及形状分析、物体追踪、特征检测和对象检测等高级算法。 4. **highgui. High-level GUI and Media I/O** - 高级GUI模块提供了创建用户界面的能力，如窗口管理、键盘和鼠标事件处理。同时，它支持读写图像和视频文件，与Qt框架的集成提供了更丰富的功能。 5. **video. Video Analysis** - 视频分析模块专注于运动分析和对象跟踪，这对于视频监控、运动检测等应用场景至关重要。 6. **calib3d. Camera Calibration and 3D Reconstruction** - 相机标定和3D重建是计算机视觉中的关键任务，这个模块提供了估计相机参数、立体视觉和单应性矩阵的方法。 7. **features2d. 2D Features Framework** - 2D特征框架包含了多种特征检测和描述算法，如SIFT、SURF、ORB等，这些特征对于对象识别和匹配至关重要。这些模块和概念构成了OpenCV的核心，使得开发者能够构建复杂而高效的计算机视觉应用。通过理解和运用OpenCV的API，开发人员可以实现图像处理、目标检测、运动分析等一系列计算机视觉任务，从而推动各种领域的创新，如自动驾驶、无人机导航、医学成像等。

The OpenCV Reference Manual, Release 2.4.3

template<typename

Tp> inline bool

operator <= (const Rect

Tp>& r1, const Rect

Tp>& r2)

{

return (r1 & r2) == r1;

}

For your convenience, the Rect

<> alias is available:

typedef Rect

<int> Rect;

RotatedRect

class RotatedRect

The class represents rotated (i.e. not up-right) rectangles on a plane. Each rectangle is speciﬁed by the center point

(mass center), length of each side (represented by cv::Size2f structure) and the rotation angle in degrees.

C++: RotatedRect::RotatedRect()

C++: RotatedRect::RotatedRect(const Point2f& center, const Size2f& size, ﬂoat angle)

C++: RotatedRect::RotatedRect(const CvBox2D& box)

Parameters

center – The rectangle mass center.

size – Width and height of the rectangle.

angle – The rotation angle in a clockwise direction. When the angle is 0, 90, 180,

270 etc., the rectangle becomes an up-right rectangle.

box – The rotated rectangle parameters as the obsolete CvBox2D structure.

C++: void RotatedRect::points(Point2f pts[]) const

C++: Rect RotatedRect::boundingRect() const

C++: RotatedRect::operator CvBox2D() const

Parameters

pts – The points array for storing rectangle vertices.

The sample below demonstrates how to use RotatedRect:

Mat image(200, 200, CV

8UC3, Scalar(0));

RotatedRect rRect = RotatedRect(Point2f(100,100), Size2f(100,50), 30);

Point2f vertices[4];

rRect.points(vertices);

for (int i = 0; i < 4; i++)

line(image, vertices[i], vertices[(i+1)%4], Scalar(0,255,0));

Rect brect = rRect.boundingRect();

rectangle(image, brect, Scalar(255,0,0));

imshow("rectangles", image);

waitKey(0);

10 Chapter 2. core. The Core Functionality

The OpenCV Reference Manual, Release 2.4.3

Ptr(

obj);

// destructor: calls release()

~Ptr();

// copy constructor; increments ptr’s reference counter

Ptr(const Ptr& ptr);

// assignment operator; decrements own reference counter

// (with release()) and increments ptr’s reference counter

Ptr& operator = (const Ptr& ptr);

// increments reference counter

void addref();

// decrements reference counter; when it becomes 0,

// delete

obj() is called

void release();

// user-specified custom object deletion operation.

// by default, "delete obj;" is called

void delete

obj();

// returns true if obj == 0;

bool empty() const;

// provide access to the object fields and methods

operator -> ();

const

operator -> () const;

// return the underlying object pointer;

// thanks to the methods, the Ptr<

Tp> can be

// used instead of

operator

();

operator const

() const;

protected:

// the encapsulated object pointer

obj;

// the associated reference counter

int

refcount;

};

The Ptr<

Tp> class is a template class that wraps pointers of the corresponding type. It is similar to shared

ptr that

is part of the Boost library ( http://www.boost.org/doc/libs/1_40_0/libs/smart_ptr/shared_ptr.htm ) and also part of the

C++0x standard.

This class provides the following options:

• Default constructor, copy constructor, and assignment operator for an arbitrary C++ class or a C structure. For

some objects, like ﬁles, windows, mutexes, sockets, and others, a copy constructor or an assignment operator

are difﬁcult to deﬁne. For some other objects, like complex classiﬁers in OpenCV, copy constructors are absent

and not easy to implement. Finally, some of complex OpenCV and your own data structures may be written in

C. However, copy constructors and default constructors can simplify programming a lot. Besides, they are often

required (for example, by STL containers). By wrapping a pointer to such a complex object TObj to Ptr<TObj>

, you automatically get all of the necessary constructors and the assignment operator.

• O(1) complexity of the above-mentioned operations. While some structures, like std::vector, provide a copy

constructor and an assignment operator, the operations may take a considerable amount of time if the data

structures are large. But if the structures are put into Ptr<> , the overhead is small and independent of the data

size.

• Automatic destruction, even for C structures. See the example below with FILE

• Heterogeneous collections of objects. The standard STL and most other C++ and OpenCV containers can store

only objects of the same type and the same size. The classical solution to store objects of different types in the

same container is to store pointers to the base class base

class

instead but then you loose the automatic

14 Chapter 2. core. The Core Functionality

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