加载，修改，保存图像
主要内容imread()函数2. cvtColor()函数3. imwrite()函数imread()函数imread函数的功能是加载一张图像，并将其存储至一个Mat类型的对象中。第一个参数为图像文件名称，可以是相对路径，也可以是绝对路径。
第二个参数就是加载图像时，读入的类型。这里我们几个参数选择。如下图所示：
示例代码：
int main(){Mat src;// 定义一个Mat类型对象 src = imread(“./1.jpg”, IMREAD_COLOR);// 读入一个图像if(src.empty()){// 当图像为空时，执行if语句判断 cout <<“img empty”<< endl;// 输出 img empty} imshow(“src”, src);// 显示图像 waitKey(0);// 设定等待时间为无限等待return0;// 返回值}
cvtColor()函数cvtColor()函数的功能是将一个图像从一个色彩空间转换到另一个色彩空间。需要三个参数，第一个参数为输入图像，第二个参数为输出图像。第三个参数为转换的色彩空间类型。
第三个参数种类如下所示： cv::ColorConversionCodes{ cv::COLOR_BGR2BGRA =0, cv::COLOR_RGB2RGBA = COLOR_BGR2BGRA, cv::COLOR_BGRA2BGR =1, cv::COLOR_RGBA2RGB = COLOR_BGRA2BGR, cv::COLOR_BGR2RGBA =2, cv::COLOR_RGB2BGRA = COLOR_BGR2RGBA, cv::COLOR_RGBA2BGR =3, cv::COLOR_BGRA2RGB = COLOR_RGBA2BGR, cv::COLOR_BGR2RGB =4, cv::COLOR_RGB2BGR = COLOR_BGR2RGB, cv::COLOR_BGRA2RGBA =5, cv::COLOR_RGBA2BGRA = COLOR_BGRA2RGBA, cv::COLOR_BGR2GRAY =6, cv::COLOR_RGB2GRAY =7, cv::COLOR_GRAY2BGR =8, cv::COLOR_GRAY2RGB = COLOR_GRAY2BGR, cv::COLOR_GRAY2BGRA =9, cv::COLOR_GRAY2RGBA = COLOR_GRAY2BGRA, cv::COLOR_BGRA2GRAY =10, cv::COLOR_RGBA2GRAY =11, cv::COLOR_BGR2BGR565 =12, cv::COLOR_RGB2BGR565 =13, cv::COLOR_BGR5652BGR =14, cv::COLOR_BGR5652RGB =15, cv::COLOR_BGRA2BGR565 =16, cv::COLOR_RGBA2BGR565 =17, cv::COLOR_BGR5652BGRA =18, cv::COLOR_BGR5652RGBA =19, cv::COLOR_GRAY2BGR565 =20, cv::COLOR_BGR5652GRAY =21, cv::COLOR_BGR2BGR555 =22, cv::COLOR_RGB2BGR555 =23, cv::COLOR_BGR5552BGR =24, cv::COLOR_BGR5552RGB =25, cv::COLOR_BGRA2BGR555 =26, cv::COLOR_RGBA2BGR555 =27, cv::COLOR_BGR5552BGRA =28, cv::COLOR_BGR5552RGBA =29, cv::COLOR_GRAY2BGR555 =30, cv::COLOR_BGR5552GRAY =31, cv::COLOR_BGR2XYZ =32, cv::COLOR_RGB2XYZ =33, cv::COLOR_XYZ2BGR =34, cv::COLOR_XYZ2RGB =35, cv::COLOR_BGR2YCrCb =36, cv::COLOR_RGB2YCrCb =37, cv::COLOR_YCrCb2BGR =38, cv::COLOR_YCrCb2RGB =39, cv::COLOR_BGR2HSV =40, cv::COLOR_RGB2HSV =41, cv::COLOR_BGR2Lab =44, cv::COLOR_RGB2Lab =45, cv::COLOR_BGR2Luv =50, cv::COLOR_RGB2Luv =51, cv::COLOR_BGR2HLS =52, cv::COLOR_RGB2HLS =53, cv::COLOR_HSV2BGR =54, cv::COLOR_HSV2RGB =55, cv::COLOR_Lab2BGR =56, cv::COLOR_Lab2RGB =57, cv::COLOR_Luv2BGR =58, cv::COLOR_Luv2RGB =59, cv::COLOR_HLS2BGR =60, cv::COLOR_HLS2RGB =61, cv::COLOR_BGR2HSV_FULL =66, cv::COLOR_RGB2HSV_FULL =67, cv::COLOR_BGR2HLS_FULL =68, cv::COLOR_RGB2HLS_FULL =69, cv::COLOR_HSV2BGR_FULL =70, cv::COLOR_HSV2RGB_FULL =71, cv::COLOR_HLS2BGR_FULL =72, cv::COLOR_HLS2RGB_FULL =73, cv::COLOR_LBGR2Lab =74, cv::COLOR_LRGB2Lab =75, cv::COLOR_LBGR2Luv =76, cv::COLOR_LRGB2Luv =77, cv::COLOR_Lab2LBGR =78, cv::COLOR_Lab2LRGB =79, cv::COLOR_Luv2LBGR =80, cv::COLOR_Luv2LRGB =81, cv::COLOR_BGR2YUV =82, cv::COLOR_RGB2YUV =83, cv::COLOR_YUV2BGR =84, cv::COLOR_YUV2RGB =85, cv::COLOR_YUV2RGB_NV12 =90, cv::COLOR_YUV2BGR_NV12 =91, cv::COLOR_YUV2RGB_NV21 =92, cv::COLOR_YUV2BGR_NV21 =93, cv::COLOR_YUV420sp2RGB = COLOR_YUV2RGB_NV21, cv::COLOR_YUV420sp2BGR = COLOR_YUV2BGR_NV21, cv::COLOR_YUV2RGBA_NV12 =94, cv::COLOR_YUV2BGRA_NV12 =95, cv::COLOR_YUV2RGBA_NV21 =96, cv::COLOR_YUV2BGRA_NV21 =97, cv::COLOR_YUV420sp2RGBA = COLOR_YUV2RGBA_NV21, cv::COLOR_YUV420sp2BGRA = COLOR_YUV2BGRA_NV21, cv::COLOR_YUV2RGB_YV12 =98, cv::COLOR_YUV2BGR_YV12 =99, cv::COLOR_YUV2RGB_IYUV =100, cv::COLOR_YUV2BGR_IYUV =101, cv::COLOR_YUV2RGB_I420 = COLOR_YUV2RGB_IYUV, cv::COLOR_YUV2BGR_I420 = COLOR_YUV2BGR_IYUV, cv::COLOR_YUV420p2RGB = COLOR_YUV2RGB_YV12, cv::COLOR_YUV420p2BGR = COLOR_YUV2BGR_YV12, cv::COLOR_YUV2RGBA_YV12 =102, cv::COLOR_YUV2BGRA_YV12 =103, cv::COLOR_YUV2RGBA_IYUV =104, cv::COLOR_YUV2BGRA_IYUV =105, cv::COLOR_YUV2RGBA_I420 = COLOR_YUV2RGBA_IYUV, cv::COLOR_YUV2BGRA_I420 = COLOR_YUV2BGRA_IYUV, cv::COLOR_YUV420p2RGBA = COLOR_YUV2RGBA_YV12, cv::COLOR_YUV420p2BGRA = COLOR_YUV2BGRA_YV12, cv::COLOR_YUV2GRAY_420 =106, cv::COLOR_YUV2GRAY_NV21 = COLOR_YUV2GRAY_420, cv::COLOR_YUV2GRAY_NV12 = COLOR_YUV2GRAY_420, cv::COLOR_YUV2GRAY_YV12 = COLOR_YUV2GRAY_420, cv::COLOR_YUV2GRAY_IYUV = COLOR_YUV2GRAY_420, cv::COLOR_YUV2GRAY_I420 = COLOR_YUV2GRAY_420, cv::COLOR_YUV420sp2GRAY = COLOR_YUV2GRAY_420, cv::COLOR_YUV420p2GRAY = COLOR_YUV2GRAY_420, cv::COLOR_YUV2RGB_UYVY =107, cv::COLOR_YUV2BGR_UYVY =108, cv::COLOR_YUV2RGB_Y422 = COLOR_YUV2RGB_UYVY, cv::COLOR_YUV2BGR_Y422 = COLOR_YUV2BGR_UYVY, cv::COLOR_YUV2RGB_UYNV = COLOR_YUV2RGB_UYVY, cv::COLOR_YUV2BGR_UYNV = COLOR_YUV2BGR_UYVY, cv::COLOR_YUV2RGBA_UYVY =111, cv::COLOR_YUV2BGRA_UYVY =112, cv::COLOR_YUV2RGBA_Y422 = COLOR_YUV2RGBA_UYVY, cv::COLOR_YUV2BGRA_Y422 = COLOR_YUV2BGRA_UYVY, cv::COLOR_YUV2RGBA_UYNV = COLOR_YUV2RGBA_UYVY, cv::COLOR_YUV2BGRA_UYNV = COLOR_YUV2BGRA_UYVY, cv::COLOR_YUV2RGB_YUY2 =115, cv::COLOR_YUV2BGR_YUY2 =116, cv::COLOR_YUV2RGB_YVYU =117, cv::COLOR_YUV2BGR_YVYU =118, cv::COLOR_YUV2RGB_YUYV = COLOR_YUV2RGB_YUY2, cv::COLOR_YUV2BGR_YUYV = COLOR_YUV2BGR_YUY2, cv::COLOR_YUV2RGB_YUNV = COLOR_YUV2RGB_YUY2, cv::COLOR_YUV2BGR_YUNV = COLOR_YUV2BGR_YUY2, cv::COLOR_YUV2RGBA_YUY2 =119, cv::COLOR_YUV2BGRA_YUY2 =120, cv::COLOR_YUV2RGBA_YVYU =121, cv::COLOR_YUV2BGRA_YVYU =122, cv::COLOR_YUV2RGBA_YUYV = COLOR_YUV2RGBA_YUY2, cv::COLOR_YUV2BGRA_YUYV = COLOR_YUV2BGRA_YUY2, cv::COLOR_YUV2RGBA_YUNV = COLOR_YUV2RGBA_YUY2, cv::COLOR_YUV2BGRA_YUNV = COLOR_YUV2BGRA_YUY2, cv::COLOR_YUV2GRAY_UYVY =123, cv::COLOR_YUV2GRAY_YUY2 =124, cv::COLOR_YUV2GRAY_Y422 = COLOR_YUV2GRAY_UYVY, cv::COLOR_YUV2GRAY_UYNV = COLOR_YUV2GRAY_UYVY, cv::COLOR_YUV2GRAY_YVYU = COLOR_YUV2GRAY_YUY2, cv::COLOR_YUV2GRAY_YUYV = COLOR_YUV2GRAY_YUY2, cv::COLOR_YUV2GRAY_YUNV = COLOR_YUV2GRAY_YUY2, cv::COLOR_RGBA2mRGBA =125, cv::COLOR_mRGBA2RGBA =126, cv::COLOR_RGB2YUV_I420 =127, cv::COLOR_BGR2YUV_I420 =128, cv::COLOR_RGB2YUV_IYUV = COLOR_RGB2YUV_I420, cv::COLOR_BGR2YUV_IYUV = COLOR_BGR2YUV_I420, cv::COLOR_RGBA2YUV_I420 =129, cv::COLOR_BGRA2YUV_I420 =130, cv::COLOR_RGBA2YUV_IYUV = COLOR_RGBA2YUV_I420, cv::COLOR_BGRA2YUV_IYUV = COLOR_BGRA2YUV_I420, cv::COLOR_RGB2YUV_YV12 =131, cv::COLOR_BGR2YUV_YV12 =132, cv::COLOR_RGBA2YUV_YV12 =133, cv::COLOR_BGRA2YUV_YV12 =134, cv::COLOR_BayerBG2BGR =46, cv::COLOR_BayerGB2BGR =47, cv::COLOR_BayerRG2BGR =48, cv::COLOR_BayerGR2BGR =49, cv::COLOR_BayerBG2RGB = COLOR_BayerRG2BGR, cv::COLOR_BayerGB2RGB = COLOR_BayerGR2BGR, cv::COLOR_BayerRG2RGB = COLOR_BayerBG2BGR, cv::COLOR_BayerGR2RGB = COLOR_BayerGB2BGR, cv::COLOR_BayerBG2GRAY =86, cv::COLOR_BayerGB2GRAY =87, cv::COLOR_BayerRG2GRAY =88, cv::COLOR_BayerGR2GRAY =89, cv::COLOR_BayerBG2BGR_VNG =62, cv::COLOR_BayerGB2BGR_VNG =63, cv::COLOR_BayerRG2BGR_VNG =64, cv::COLOR_BayerGR2BGR_VNG =65, cv::COLOR_BayerBG2RGB_VNG = COLOR_BayerRG2BGR_VNG, cv::COLOR_BayerGB2RGB_VNG = COLOR_BayerGR2BGR_VNG, cv::COLOR_BayerRG2RGB_VNG = COLOR_BayerBG2BGR_VNG, cv::COLOR_BayerGR2RGB_VNG = COLOR_BayerGB2BGR_VNG, cv::COLOR_BayerBG2BGR_EA =135, cv::COLOR_BayerGB2BGR_EA =136, cv::COLOR_BayerRG2BGR_EA =137, cv::COLOR_BayerGR2BGR_EA =138, cv::COLOR_BayerBG2RGB_EA = COLOR_BayerRG2BGR_EA, cv::COLOR_BayerGB2RGB_EA = COLOR_BayerGR2BGR_EA, cv::COLOR_BayerRG2RGB_EA = COLOR_BayerBG2BGR_EA, cv::COLOR_BayerGR2RGB_EA = COLOR_BayerGB2BGR_EA, cv::COLOR_BayerBG2BGRA =139, cv::COLOR_BayerGB2BGRA =140, cv::COLOR_BayerRG2BGRA =141, cv::COLOR_BayerGR2BGRA =142, cv::COLOR_BayerBG2RGBA = COLOR_BayerRG2BGRA, cv::COLOR_BayerGB2RGBA = COLOR_BayerGR2BGRA, cv::COLOR_BayerRG2RGBA = COLOR_BayerBG2BGRA, cv::COLOR_BayerGR2RGBA = COLOR_BayerGB2BGRA, cv::COLOR_COLORCVT_MAX =143}<
示例代码：
int main(){Mat src;// 定义一个Mat类型对象Mat src_gray;// 定义一个Mat类型对象 src = imread(“./1.jpg”, IMREAD_COLOR);// 读入一个图像if(src.empty()){// 当图像为空时，执行if语句判断 cout <<“img empty”<< endl;// 输出 img empty} imshow(“src”, src);// 显示图像 cvtColor(src, src_gray, COLOR_RGB2GRAY);// 将src转换为灰度图像存储至src_gray waitKey(0);// 设定等待时间为无限等待return0;// 返回值}imwrite()函数imwrite()函数的功能是将图像保存到指定的路径下。参数有两个。第一个是存储路径，第二个是待存储的Mat对象。这个函数比较简单没什么好解释的。
示例代码： int main(){Mat src;// 定义一个Mat类型对象Mat src_gray;// 定义一个Mat类型对象 src = imread(“./1.jpg”, IMREAD_COLOR);// 读入一个图像if(src.empty()){// 当图像为空时，执行if语句判断 cout <<“img empty”<< endl;// 输出 img empty} imshow(“src”, src);// 显示图像 cvtColor(src, src_gray, COLOR_RGB2GRAY);// 将src转换为灰度图像存储至src_gray imwrite(“./save.jpg”, src_gray);// 将src_gray这个图像存储到相对路径下，并且命名为save.jpg waitKey(0);// 设定等待时间为无限等待return0;// 返回值}
