簡介
本篇主要是利用三張圖片：過曝(相機設置exposure+1)、正常(相機設置exposure+0)、欠曝(相機設置exposure-1)，來合成一張在亮出和暗處細節都清晰
的圖片，來簡易實現圖片的HDR功能。
具體實現
實現代碼
1 #include <opencv2/core/core.hpp>
2 #include <opencv2/highgui/highgui.hpp>
3 #include <math.h>
4 #include <string.h>
5 #include <opencv/cv.h>
6 #include <stdio.h>
7 #include "opencv2/photo/photo.hpp"
8
9 using namespace cv; 10
11 char highpicName[20]; 12 char normalpicName[20]; 13 char lowpicName[20]; 14 Mat mat1, mat2, mat3, dst_mat, tmp_mat; 15 int highWidth, highHeight; 16 int normalWidth, normalHeight; 17 int lowWidth, lowHeight; 18 IplImage src1, src2, src3, dst_src, tmp_src; 19 double weight=0.5; 20
21
22 void hdrCale(Mat pic1, Mat pic2, Mat pic3){ 23 int i, j; 24 CvScalar s1, s2, s3; 25
26
27 src1 = pic1; 28 src2 = pic2; 29 src3 = pic3; 30 dst_src = dst_mat; 31 tmp_src = tmp_mat; 32
33 cvCvtColor(&src2, &tmp_src, CV_BGR2GRAY); 34 for(i=0; i< normalWidth; i++){ 35 for(j=0; j<normalHeight; j++){ 36 s1 = cvGet2D(&src1, i, j); 37 s2 = cvGet2D(&tmp_src, i, j); 38 s3 = cvGet2D(&src3, i, j); 39 weight = 0.5 + (127 - s2.val[0]) * 0.002; 40 s3.val[0] = (s1.val[0] * weight) + (s3.val[0] * (1-weight)); 41 s3.val[1] = (s1.val[1] * weight) + (s3.val[1] * (1-weight)); 42 s3.val[2] = (s1.val[2] * weight) + (s3.val[2] * (1-weight)); 43 cvSet2D(&dst_src, i, j, s3); 44 } 45 } 46 } 47
48
49 int main(int argc, char *argv[]){ 50 if(argc < 4){ 51 printf("Please input high exposure/normal exposure/low exposure picture!\n"); 52 return -1; 53 } 54 memcpy(highpicName, argv[1], sizeof(argv[1])); 55 memcpy(normalpicName, argv[2], sizeof(argv[2])); 56 memcpy(lowpicName, argv[3], sizeof(argv[3])); 57 mat1 = imread(argv[1]); 58 mat2 = imread(argv[2]); 59 mat3 = imread(argv[3]); 60 highWidth = mat1.rows; 61 highHeight = mat1.cols; 62 normalWidth = mat2.rows; 63 normalHeight = mat2.cols; 64 lowWidth = mat3.rows; 65 lowHeight = mat3.cols; 66 dst_mat = Mat(normalWidth, normalHeight, CV_8UC3, cv::Scalar(0, 0, 0)); 67 tmp_mat = Mat(normalWidth, normalHeight, CV_8UC1, cv::Scalar(0, 0, 0)); 68
69 hdrCale(mat1, mat2, mat3); 70
71 imshow("normal", mat2); 72 imshow("HDR", dst_mat); 73 imwrite("HDR.jpg", dst_mat); 74 cv::waitKey(0); 75 return 0; 76 }
代碼講解
1、首先進行相對應的初始化操作：運行軟件時候，需要傳入三張圖片，順序上分別是：過曝、正常、欠曝。打開這三張圖片，保存在mat1、mat2、mat3
中，注意這三張圖片必須大小一致。接着獲取到圖片的width和height。最后創建兩張空白圖片：tmp_mat和dst_mat。
1 if(argc < 4){ 2 printf("Please input high exposure/normal exposure/low exposure picture!\n"); 3 return -1; 4 } 5 memcpy(highpicName, argv[1], sizeof(argv[1])); 6 memcpy(normalpicName, argv[2], sizeof(argv[2])); 7 memcpy(lowpicName, argv[3], sizeof(argv[3])); 8 mat1 = imread(argv[1]); 9 mat2 = imread(argv[2]); 10 mat3 = imread(argv[3]); 11 highWidth = mat1.rows; 12 highHeight = mat1.cols; 13 normalWidth = mat2.rows; 14 normalHeight = mat2.cols; 15 lowWidth = mat3.rows; 16 lowHeight = mat3.cols; 17 dst_mat = Mat(normalWidth, normalHeight, CV_8UC3, cv::Scalar(0, 0, 0)); 18 tmp_mat = Mat(normalWidth, normalHeight, CV_8UC1, cv::Scalar(0, 0, 0));
2、接着進入到HDR的算法處理：對應的處理很簡單，主要就是根據就是權重，把過曝和欠曝圖片合成到dst_mat中。
具體做法：循環依次打開三張圖片的同一位置像素，用正常曝光圖片像素，利用公式：weight = 0.5 + (127 - s2.val[0]) * 0.002;
來獲得使用過曝、欠曝像素合成到dst_mat中對應使用的權值。接着：s3.val[0] = (s1.val[0] * weight) + (s3.val[0] * (1-weight));
計算出合成像素值之后，寫入到dst_mat對應的坐標位置。進而生成HDR照片。
1 void hdrCale(Mat pic1, Mat pic2, Mat pic3){ 2 int i, j; 3 CvScalar s1, s2, s3; 4
5 src1 = pic1; 6 src2 = pic2; 7 src3 = pic3; 8 dst_src = dst_mat; 9 tmp_src = tmp_mat; 10
11 cvCvtColor(&src2, &tmp_src, CV_BGR2GRAY); 12 for(i=0; i< normalWidth; i++){ 13 for(j=0; j<normalHeight; j++){ 14 s1 = cvGet2D(&src1, i, j); 15 s2 = cvGet2D(&tmp_src, i, j); 16 s3 = cvGet2D(&src3, i, j); 17 weight = 0.5 + (127 - s2.val[0]) * 0.002; 18 s3.val[0] = (s1.val[0] * weight) + (s3.val[0] * (1-weight)); 19 s3.val[1] = (s1.val[1] * weight) + (s3.val[1] * (1-weight)); 20 s3.val[2] = (s1.val[2] * weight) + (s3.val[2] * (1-weight)); 21 cvSet2D(&dst_src, i, j, s3); 22 } 23 } 24 }
3、最后將正常照片和HDR照片顯示初戀，並將hdr照片保存下來。
1 imshow("normal", mat2); 2 imshow("HDR", dst_mat); 3 imwrite("HDR.jpg", dst_mat); 4 cv::waitKey(0);
效果演示
對應的效果演示如下:
過曝圖像：
正常圖像
欠曝圖像：
HDR圖像
