OpenCV（5） 对比度和亮度

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公式：

两个参数 \alpha > 0 和 \beta 一般称作 增益 和 偏置 参数。我们往往用这两个参数来分别控制 对比度 和 亮度 。

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1. #include "stdafx.h"
2. #include<iostream>
3. #include<thread>
4. #include<vector>
5. #include <opencv2/core/core.hpp>
6. #include <opencv2/contrib/contrib.hpp>
7. #include <opencv2/highgui/highgui.hpp>
8. #include <opencv2/imgproc/imgproc.hpp>
9. #include <opencv2/objdetect/objdetect.hpp>
10. ?
11. using
    namespace cv;
12. using
    namespace std;
13. ?
14. int g_slider_position = 0, g_slider_position2 = 0;
15. Mat image;
16. Mat new_image;
17. double alpha, beta;
18. ?
19. void onTrackingbarSlide(int pos)
20. {
21. ???new_image = Mat::zeros(image.size(), image.type());
22. ???beta = pos;
23. ???for (int y = 0; y < image.rows; y++)
24. ???{
25. ??????for (int x = 0; x < image.cols; x++)
26. ??????{
27. ?????????for (int c = 0; c < 3; c++)
28. ?????????{
29. ????????????//saturate_cast 防止数据溢出
30. ????????????new_image.at<Vec3b>(y, x)[c] = saturate_cast<uchar>(alpha*(image.at<Vec3b>(y, x)[c]) + beta);
31. ?????????}
32. ??????}
33. ???}
34. ?
35. ???imshow("New Image", new_image);
36. }
37. ?
38. void onTrackingbarSlide2(int pos)
39. {
40. ???new_image = Mat::zeros(image.size(), image.type());
41. ?
42. ???alpha = (double)pos / 10.0;
43. ?
44. ???for (int y = 0; y < image.rows; y++)
45. ???{
46. ??????for (int x = 0; x < image.cols; x++)
47. ??????{
48. ?????????for (int c = 0; c < 3; c++)
49. ?????????{
50. ????????????//saturate_cast 防止数据溢出
51. ????????????new_image.at<Vec3b>(y, x)[c] = saturate_cast<uchar>(alpha*(image.at<Vec3b>(y, x)[c]) + beta);
52. ?????????}
53. ??????}
54. ???}
55. ?
56. ???imshow("New Image", new_image);
57. }
58. ?
59. int _tmain(int argc, _TCHAR* argv[])
60. {
61. ???/// 读入用户提供的图像
62. ???image = imread("E:\\myImage\\sql.png");
63. ?
64. ???//初始化为0的数组
65. ???Mat new_image = Mat::zeros(image.size(), image.type());
66. ?
67. ???/// 初始化
68. ???cout << "* Enter the alpha value [1.0-3.0]: ";
69. ???cin >> alpha;
70. ???cout << "* Enter the beta value [0-100]: ";
71. ???cin >> beta;
72. ?
73. ???/// 创建窗口
74. ???namedWindow("Original Image", 1); // 1:WINDOW_AUTOSIZE
75. ???namedWindow("New Image", 1);
76. ?
77. ???cvCreateTrackbar("亮度（增益）", "New Image", &g_slider_position, 100, onTrackingbarSlide);
78. ???cvCreateTrackbar("对比度（偏置）", "New Image", &g_slider_position2, 30, onTrackingbarSlide2);
79. ?
80. ???/// 执行运算 new_image(i,j) = alpha*image(i,j) + beta
81. ???for (int y = 0; y < image.rows; y++)
82. ???{
83. ??????for (int x = 0; x < image.cols; x++)
84. ??????{
85. ?????????for (int c = 0; c < 3; c++)
86. ?????????{
87. ????????????//saturate_cast 防止数据溢出
88. ????????????new_image.at<Vec3b>(y, x)[c] = saturate_cast<uchar>(alpha*(image.at<Vec3b>(y, x)[c]) + beta);
89. ?????????}
90. ??????}
91. ???}
92. ?
93. ???/// 显示图像
94. ???imshow("Original Image", image);
95. ???imshow("New Image", new_image);
96. ?
97. ???/// 等待用户按键
98. ???waitKey();
99. ???return 0;
100. }

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参考：

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