跟我一起學opencv 第五課之調整圖像亮度和對比度
阿新 • • 發佈:2019-04-28
key 代碼 urn name -- 修改 圖像 load auto
一.調整圖像亮度與對比度
1.圖像變換
---像素變換-點操作
---鄰域操作-區域操作
調整圖像亮度和對比度屬於像素變換-點操作
公式為:g(i,j) = αf(i,j) + β 其中α>0 ,β是增益變量
處理圖像經常會對圖像色彩進行增強,這就是改變圖像的亮度β和對比度α,
我們看看實例代碼:
1 #include<opencv2\opencv.hpp> 2 #include<iostream> 3 4 using namespace std; 5 usingnamespace cv; 6 /*圖像操作*/ 7 int main(int argc, char **argv) 8 { 9 Mat src1 = imread("E:\\vsprom\\learn05\\v15.jpg"); 10 11 if (src1.empty()) 12 { 13 cout << "can not load imagefile1...." << endl; 14 return -1; 15 } 16 namedWindow("in1 image win", CV_WINDOW_AUTOSIZE); 17 imshow("in1 image win", src1); 18 19 int height = src1.rows; 20 int width = src1.cols; 21 22 Mat dst = Mat::zeros(src1.size(), src1.type());//創建一副與src1同樣的圖像,並將像素值全部給0 23 float alpha = 1.2; 24 float beta = 30; 25 for (int row = 0; row < height; row++)26 { 27 for (int col = 0; col < width; col++) 28 { 29 if (src1.channels() == 3)//三通道圖像 30 { 31 float b = src1.at<Vec3b>(row, col)[0];//通道1 32 float g = src1.at<Vec3b>(row, col)[1];//通道2 33 float r = src1.at<Vec3b>(row, col)[2];//通道3 34 35 dst.at<Vec3b>(row, col)[0] = saturate_cast<uchar>(b*alpha + beta);//使用公式 36 dst.at<Vec3b>(row, col)[1] = saturate_cast<uchar>(g*alpha + beta); 37 dst.at<Vec3b>(row, col)[2] = saturate_cast<uchar>(r*alpha + beta); 38 39 } 40 else if (src1.channels() == 1)//單通道圖像 41 { 42 float v = src1.at<uchar>(row, col); 43 dst.at<uchar>(row, col) = saturate_cast<uchar>(v*alpha + beta); 44 } 45 } 46 } 47 namedWindow("dst image win", CV_WINDOW_AUTOSIZE); 48 imshow("dst image win", dst); 49 50 51 waitKey(0); 52 return 0; 53 }
效果如下此時α=1.2,β=30
效果如下α=1.2,β=100時,此時更亮
效果如下α=5,β=30時,對比更明顯
轉換圖像格式:
src2.convertTo(src1, CV_32F);
代碼為:
#include<opencv2\opencv.hpp> #include<iostream> using namespace std; using namespace cv; /*圖像操作*/ int main(int argc, char **argv) { Mat src2 = imread("E:\\vsprom\\learn05\\v15.jpg"); if (src2.empty()) { cout << "can not load imagefile1...." << endl; return -1; } namedWindow("in1 image win", CV_WINDOW_AUTOSIZE); imshow("in1 image win", src2); Mat src1; src2.convertTo(src1, CV_32F); int height = src1.rows; int width = src1.cols; Mat dst = Mat::zeros(src2.size(), src2.type());//創建一副與src1同樣的圖像,並將像素值全部給0 float alpha = 1.2; float beta = 30; for (int row = 0; row < height; row++) { for (int col = 0; col < width; col++) { if (src1.channels() == 3)//三通道圖像 { float b = src1.at<Vec3f>(row, col)[0];//通道1 float g = src1.at<Vec3f>(row, col)[1];//通道2 float r = src1.at<Vec3f>(row, col)[2];//通道3 //修改像素值 dst.at<Vec3b>(row, col)[0] = saturate_cast<uchar>(b*alpha + beta); dst.at<Vec3b>(row, col)[1] = saturate_cast<uchar>(g*alpha + beta); dst.at<Vec3b>(row, col)[2] = saturate_cast<uchar>(r*alpha + beta); } else if (src1.channels() == 1)//單通道圖像 { float v = src1.at<uchar>(row, col); dst.at<uchar>(row, col) = saturate_cast<uchar>(v*alpha + beta); } } } namedWindow("dst image win", CV_WINDOW_AUTOSIZE); imshow("dst image win", dst); waitKey(0); return 0; }
效果圖:
跟我一起學opencv 第五課之調整圖像亮度和對比度