OpenCV4.5 报错error：‘ CV_* ’was not declared in this scope 解决解决办法总结
1. CV_LOAD_IMAGE_UNCHANGED和CV_LOAD_IMAGE_COLOR
错误内容：
‘CV_LOAD_IMAGE_UNCHANGED‘ : undeclared identifier
error: ‘CV_LOAD_IMAGE_COLOR’ was not declared in this scope
解决办法：
//添加头文件 #include "opencv2/imgcodecs/legacy/constants_c.h"
2. CV_AA
错误内容：
error: ‘CV_AA’ was not declared in this scope
解决办法：
//添加头文件 #include <opencv2/imgproc/imgproc_c.h>
3. CV_CALIB_CB_ADAPTIVE_THRESH
错误内容：
error: ‘CV_CALIB_CB_ADAPTIVE_THRESH’ was not declared in this scope
解决办法：
//添加头文件 #include <opencv2/calib3d/calib3d_c.h>
4. CV_GRAY2BGR
错误内容：
error: ‘CV_GRAY2BGR’ was not declared in this scope
解决办法：
更改代码
//代码改为 cv::COLOR_GRAY2BGR
添加头文件
//添加头文件 #include <opencv2/imgproc/types_c.h>
5. CV_THRESH_BINARY_INV / CV_CHAIN_APPROX_SIMPLE / CV_RETR_CCOMP / CV_FONT_HERSHEY_SIMPLEX
错误内容：
error: ‘CV_THRESH_BINARY_INV’ was not declared in this scope
error: ‘CV_CHAIN_APPROX_SIMPLE’ was not declared in this scope
error: ‘CV_RETR_CCOMP’ was not declared in this scope
error: ‘CV_FONT_HERSHEY_SIMPLEX’ was not declared in this scope
解决办法：
//代码改为 cv::THRESH_BINARY_INV cv::CHAIN_APPROX_SIMPLE cv::RETR_CCOMP cv::FONT_HERSHEY_SIMPLEX
6. CV_LOAD_IMAGE_GRAYSCALE
错误内容：
error: ‘CV_LOAD_IMAGE_GRAYSCALE’ was not declared in this scope
解决办法：
//代码改为 cv::IMREAD_COLOR
7. CV_FM_8POINT
错误内容：
error: ‘CV_FM_8POINT’ was not declared in this scope
解决办法：
更改代码
//更改前 CV_FM_8POINTT //更改后 FM_8POINT
添加头文件
#include <opencv2/opencv.hpp>
8. CV_FILLED
错误内容：
error: ‘CV_FILLED’ was not declared in this scope
解决办法：
// 添加头文件 #include <opencv2/imgproc/imgproc_c.h>
9. CV_MINMAX
错误内容：
error: ‘CV_MINMAX’ was not declared in this scope
解决办法：
// 添加头文件 #include<opencv2/opencv.hpp>
10. CV_RGB2GRAY
错误内容：
error: ‘CV_RGB2GRAY’ was not declared in this scope
解决办法：
// 添加头文件 #include <opencv2/highgui/highgui_c.h>
11. CV_ADAPTIVE_THRESH_MEAN_C
错误内容：
error: ‘CV_ADAPTIVE_THRESH_MEAN_C’ was not declared in this scope
解决办法：
// 添加头文件 #include <opencv2/calib3d/calib3d_c.h>
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