OpenCV Basics - Miscellaneous
1. <opencv2/opencv.hpp>
该文件已经包含了各模块头文件：
#ifndef __OPENCV_ALL_HPP__
#define __OPENCV_ALL_HPP__
#include "opencv2/core.hpp"
#include "opencv2/imgproc.hpp"
#include "opencv2/photo.hpp"
#include "opencv2/video.hpp"
#include "opencv2/features2d.hpp"
#include "opencv2/objdetect.hpp"
#include "opencv2/calib3d.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/videoio.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/ml.hpp"
#endif原则上，在写opencv程序时，可以只包含头文件opencv.hpp，这样可以精简优化代码
2. CV_VERSION
cout该宏，可以检查程序所用的OpenCV库的版本号
3. imwrite
vector<int>compression_params;
compression_params.push_back(IMWRITE_PNG_COMPRESSION);
compression_params.push_back(9);
imwrite("存图名称.png", mat, compression_params);- JPEG：params表示0到100的图片质量（CV_IMWRITE_JPEG_QUALITY），默认值为95
- PNG：params表示压缩级别（CV_IMWRITE_PNG_COMPRESSION），从0到9，其值越大，压缩尺寸越小，压缩时间越长；
- PPM / PGM / PBM：params表示二进制格式标志（CV_IMWRITE_PXM_BINARY），取值为0或1，默认是1。
4. imshow - OpenGL show GpuMat
cuda::GpuMat d_image;
d_image.upload(image);
namedWindow("Gpumat", WINDOW_OPENGL); // 设定支持OpenGL!
cuda::cvtColor(d_image, d_image, cv::COLOR_BGR2GRAY);
imshow("Gpumat", d_image);
moveWindow("Gpumat", 0, 200 ); // window也可以移动!5. TrackBar Useage
6. Mouse Useage
7. Rect
Rect rect = rect1 | rect2; // 矩形交集
rect = rect1 & rect2; // 矩形并集
rect = rect + Point(20, -10); // 矩形平移
rect = rect + Size(-30, -30); // 矩形缩放8. Get Time
double time0 = static_cast<double>(cv::getTickCount());
// do sth. to timing
time0 = ((double)cv::getTickCount() - time0)/cv::getTickFrequency();9. LUT
批量进行图像元素的查找、扫描与操作
Mat lookupTable(1, 256, CV_8U);
// lookupTable 赋值，映射hash查表
cv::LUT(I, lookupTable, O);另，cv::HammingLUT，用于计算hamming距离
unsigned char a[3] = {1,2,3}, b[3] = {2,3,4};
cv::HammingLUT lut;
std::cout << lut(a,b,3) << std::endl; // 6 = 2+1+310. cv::saturate_cast
防止越界，越界则取最大值