OpenCV Jpeg编解码

源码来自：https://code.google.com/p/opencvjp-sample/source/browse/trunk/cpp/encode_decode_test.cpp?r=63

描述：描述读取一张图片进行jpg和png压缩，并解压显示。

主要函数：imencode和imdecode。

环境：windows7+vs2010+opencv2.4.8。

工程地址：http://download.csdn.net/detail/chengkun183/7609491

源码：

1. // JPEGDecodeEncode.cpp : 定义控制台应用程序的入口点。

2.  

3. #include "stdafx.h"

4. #include <iostream>

5. #include <fstream>

6. #include <cv.h>

7. #include <highgui.h>

8. using namespace std;

9. using namespace cv;

10.  

11. double getPSNR(Mat& src1, Mat& src2, int bb=0);

12.  

13. int main(int argc, char** argv)

14. {

15. Mat src = imread("lena.png");

16. cout<<"origin image size: "<<src.dataend-src.datastart<<endl;

17. cout<<"height: "<<src.rows<<endl<<"width: "<<src.cols<<endl<<"depth: "<<src.channels()<<endl;

18. cout<<"height*width*depth: "<<src.rows*src.cols*src.channels()<<endl<<endl;

19. //(1) jpeg compression

20. vector<uchar> buff;//buffer for coding

21. vector<int> param = vector<int>(2);

22. param[0]=CV_IMWRITE_JPEG_QUALITY;

23. param[1]=95;//default(95) 0-100

24.  

25. imencode(".jpg",src,buff,param);

26. cout<<"coded file size(jpg): "<<buff.size()<<endl;//fit buff size automatically.

27. Mat jpegimage = imdecode(Mat(buff),CV_LOAD_IMAGE_COLOR);

28.  

29. //(2) png compression

30. param[0]=CV_IMWRITE_PNG_COMPRESSION;

31. param[1]=3;//default(3) 0-9.

32. imencode(".png",src,buff,param);

33. cout<<"coded file size(png): "<<buff.size()<<endl;

34. Mat pngimage = imdecode(Mat(buff),CV_LOAD_IMAGE_COLOR);

35.  

36. //(3) intaractive jpeg compression

37. char name[64];

38. namedWindow("jpg");

39. int q=95;

40. createTrackbar("quality","jpg",&q,100);

41. int key = 0;

42. while(key!='q')

43. {

44. param[0]=CV_IMWRITE_JPEG_QUALITY;

45. param[1]=q;

46. imencode(".jpg",src,buff,param);

47. Mat show = imdecode(Mat(buff),CV_LOAD_IMAGE_COLOR);

48.  

49. double psnr = getPSNR(src,show);//get PSNR

50. double bpp = 8.0*buff.size()/(show.size().area());//bit/pixe;

51. sprintf(name,"quality:%03d, %.1fdB, %.2fbpp",q,psnr,bpp);

52. putText(show,name,Point(15,50), FONT_HERSHEY_SIMPLEX,1,CV_RGB(255,255,255),2);

53. imshow("jpg",show);

54. key = waitKey(33);

55.  

56. if(key =='s')

57. {

58. //(4) data writing

59. sprintf(name,"q%03d_%.2fbpp.png",q,bpp);

60. imwrite(name,show);

61.  

62. sprintf(name,"q%03d_%.2fbpp.jpg",q,bpp);

63. param[0]=CV_IMWRITE_JPEG_QUALITY;

64. param[1]=q;

65. imwrite(name,src,param);;

66. }

67. }

68. }

69. double getPSNR(Mat& src1, Mat& src2, int bb)

70. {

71. int i,j;

72. double sse,mse,psnr;

73. sse = 0.0;

74.  

75. Mat s1,s2;

76. cvtColor(src1,s1,CV_BGR2GRAY);

77. cvtColor(src2,s2,CV_BGR2GRAY);

78.  

79. int count=0;

80. for(j=bb;j<s1.rows-bb;j++)

81. {

82. uchar* d=s1.ptr(j);

83. uchar* s=s2.ptr(j);

84.  

85. for(i=bb;i<s1.cols-bb;i++)

86. {

87. sse += ((d[i] - s[i])*(d[i] - s[i]));

88. count++;

89. }

90. }

91. if(sse == 0.0 || count==0)

92. {

93. return 0;

94. }

95. else

96. {

97. mse =sse /(double)(count);

98. psnr = 10.0*log10((255*255)/mse);

99. return psnr;

100. }

101. }

使用的图片为lena.png:

 

 

输出的信息：