OpenCV (5) Contrast and brightness

?

Formula:

Two parameters \alpha > 0 and \beta are generally referred to as gain and offset parameters. We often use these two parameters to control the contrast and brightness separately.

?

2. #include "stdafx.h"
4. #include <iostream>
6. #include <thread>
8. #include <vector>
10. #include <opencv2/core/core.hpp>
12. #include <opencv2/contrib/contrib.hpp>
14. #include <opencv2/highgui/highgui.hpp>
16. #include <opencv2/imgproc/imgproc.hpp>
18. #include <opencv2/objdetect/objdetect.hpp>
20. ?
22. using namespace CV;
24. using namespace std;
26. ?
28. int g_slider_position = 0, g_slider_position2 = 0;
30. Mat image;
32. Mat New_image;
34. double alpha, beta;
36. ?
38. void ontrackingbarslide (int POS)
40. {
42. ??? New_image = Mat::zeros (Image.size (), Image.type ());
44. ??? beta = pos;
46. ??? for (int y = 0; y < image.rows; y++)
48. ??? {
50. ?????? for (int x = 0; x < image.cols; × x + +)
52. ?????? {
54. ????????? for (int c = 0; c < 3; C + +)
56. ????????? {
58. ???????????? //saturate_cast prevent data overflow
60. ???????????? New_image.at<vec3b> (y, x) [c] = saturate_cast<uchar> (alpha* (image.at<vec3b> (y, x) [C]) + beta);
62. ?????????}
64. ??????}
66. ???}
68. ?
70. ??? Imshow ("New Image", new_image);
72. }
74. ?
76. void onTrackingbarSlide2 (int POS)
78. {
80. ??? New_image = Mat::zeros (Image.size (), Image.type ());
82. ?
84. ??? Alpha = (double) pos/10.0;
86. ?
88. ??? for (int y = 0; y < image.rows; y++)
90. ??? {
92. ?????? for (int x = 0; x < image.cols; × x + +)
94. ?????? {
96. ????????? for (int c = 0; c < 3; C + +)
98. ????????? {
100. ???????????? //saturate_cast prevent data overflow
102. ???????????? New_image.at<vec3b> (y, x) [c] = saturate_cast<uchar> (alpha* (image.at<vec3b> (y, x) [C]) + beta);
104. ?????????}
106. ??????}
108. ???}
110. ?
112. ??? Imshow ("New Image", new_image);
114. }
116. ?
118. int _tmain (int argc, _tchar* argv[])
120. {
122. ??? /// read into user-supplied images
124. ??? Image = Imread ("e:\\myimage\\sql.png");
126. ?
128. ??? //initialized to 0 array
130. ??? Mat new_image = Mat::zeros (Image.size (), Image.type ());
132. ?
134. ??? /// Initialize
136. ??? cout << "* Enter the alpha value [1.0-3.0]: ";
138. ??? CIN >> Alpha;
140. ??? cout << "* Enter the beta value [0-100]: ";
142. ??? CIN >> Beta;
144. ?
146. ??? // Create window
148. ??? Namedwindow ("Original Image", 1); //1:window_autosize
150. ??? Namedwindow ("New Image", 1);
152. ?
154. ??? Cvcreatetrackbar (" brightness (Gain)", "New Image", &g_slider_position, Ontrackingbarslide);
156. ??? Cvcreatetrackbar (" contrast (offset)", "New Image", &g_slider_position2, OnTrackingbarSlide2);
158. ?
160. ??? ///Perform operation new_image (i,j) = Alpha*image (i,j) + Beta
162. ??? for (int y = 0; y < image.rows; y++)
164. ??? {
166. ?????? for (int x = 0; x < image.cols; × x + +)
168. ?????? {
170. ????????? for (int c = 0; c < 3; C + +)
172. ????????? {
174. ???????????? //saturate_cast prevent data overflow
176. ???????????? New_image.at<vec3b> (y, x) [c] = saturate_cast<uchar> (alpha* (image.at<vec3b> (y, x) [C]) + beta);
178. ?????????}
180. ??????}
182. ???}
184. ?
186. ??? /// display image
188. ??? Imshow ("Original image", image);
190. ??? Imshow ("New Image", new_image);
192. ?
194. ??? /// wait for user keys
196. ??? Waitkey ();
198. ??? return 0;
200. }

?

?

Reference:

Http://www.opencv.org.cn/opencvdoc/2.3.2/html/doc/tutorials/core/basic_linear_transform/basic_linear_ Transform.html#basic-linear-transform

http://blog.csdn.net/mjlsuccess/article/details/12401839

OpenCV (5) Contrast and brightness