方法1:
for( int i = 0; i < I.rows; ++i)
for( int j = 0; j < I.cols; ++j )
I.at<uchar>(i,j) = 255 - I.at<uchar>(i,j);
方法2:
for( i = 0; i < nRows; ++i){
p = I.ptr<uchar>(i);
for ( j = 0; j < nCols; ++j){
p[j] = 255 - p[j];
}
}
方法3:
MatIterator_<uchar> it, end;
for( it = I.begin<uchar>(), end = I.end<uchar>(); it != end; ++it)
*it = 255 - *it;
方法4:
opencv提供的映射关系
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
using namespace cv;
Mat applyLookUp(const cv::Mat& image,const cv::Mat& lookup) {
Mat result;
cv::LUT(image,lookup,result);
return result;
}
int main( int, char** argv )
{
Mat image,gray;
image = imread( argv[1], 1 );
if( !image.data )
return -1;
cvtColor(image, gray, CV_BGR2GRAY);
Mat lut(1,256,CV_8U);
for (int i=0; i<256; i++) {
lut.at<uchar>(i)= 255-i;
}
Mat out = applyLookUp(gray,lut);
namedWindow("sample");
imshow("sample",out);
waitKey(0);
return 0;
}
耗时:
第一种:On-The-Fly RA93.7878 milliseconds
第二种:Efficient Way79.4717 milliseconds
第三种:Iterator83.7201 milliseconds
第四种:LUT function32.5759 milliseconds