奇怪的輸出，同時在OpenCV中找到一個視頻幀的熵

Question

#include <cv.h> 
#include <highgui.h> 
#include <iostream> 
#include <cmath> 
#include <cstdlib> 
#include <fstream> 

using namespace std; 

typedef struct histBundle { 
double rCh[256]; 
double gCh[256]; 
double bCh[256]; 
}bundleForHist; 

bundleForHist getHistFromImage (IplImage* img, int numBins) { 
float range[] = { 
    0, 
    numBins 
}; 
float *ranges[] = { 
    range 
}; 

bundleForHist bfh; 

CvHistogram *hist = cvCreateHist (1, &numBins, CV_HIST_ARRAY, ranges, 1); 
cvClearHist (hist); 
IplImage* imgRed = cvCreateImage(cvGetSize(img), 8, 1); 
IplImage* imgGreen = cvCreateImage(cvGetSize(img), 8, 1); 
IplImage* imgBlue = cvCreateImage(cvGetSize(img), 8, 1); 
cvSplit(img, imgBlue, imgGreen, imgRed, NULL); 
cvCalcHist(&imgRed, hist, 0, 0); 
for (int i = 0; i < numBins; ++i) { 
    bfh.rCh[i] = cvQueryHistValue_1D(hist, i); 
} 
cvClearHist(hist); 
cvCalcHist(&imgGreen, hist, 0, 0); 
for (int i = 0; i < numBins; ++i) { 
    bfh.gCh[i] = cvQueryHistValue_1D(hist, i); 
} 
cvClearHist(hist); 
cvCalcHist(&imgBlue, hist, 0, 0); 
for (int i = 0; i < numBins; ++i) { 
    bfh.bCh[i] = cvQueryHistValue_1D(hist, i); 
} 
cvClearHist(hist); 
return bfh; 
} 

int main (int argc, char** argv) { 
int c; 
IplImage* img = NULL; 
int frame_number = 0; 
CvCapture* capture = cvCaptureFromAVI ("Cricketc1.avi"); 
assert(capture); 
int fps = (int)cvGetCaptureProperty(capture, CV_CAP_PROP_FPS); 
cvNamedWindow ("Video", 0); 

while (1) { 
    //IplImage * img = cvLoadImage("C:\\Users\\ANIMES~1\\Desktop\\bw.jpg"); 
    img = cvQueryFrame(capture); 
    frame_number++; 
    if (img) { 
     cvShowImage("Video", img); 
     int numBins = 256; 
     bundleForHist bfh; 
     bfh = getHistFromImage (img, numBins); 
     double totalForR = 0; 
     double totalForG = 0; 
     double totalForB = 0; 
     double probR[256]; 
     double probG[256]; 
     double probB[256]; 
     for (int i = 0; i < numBins-1; ++i) { 
      totalForR += bfh.rCh[i]; 
      totalForG += bfh.gCh[i]; 
      totalForB += bfh.bCh[i]; 
     } 
     double lengthHistogram = totalForR + totalForG + totalForB; 
     for (int i = 0; i < 256; ++i) { 
      probR[i] = bfh.rCh[i]/(double)lengthHistogram; 
      probG[i] = bfh.gCh[i]/(double)lengthHistogram; 
      probB[i] = bfh.bCh[i]/(double)lengthHistogram; 
      //file << bfh.rCh[i] << "\t" << bfh.gCh[i] << "\t" << bfh.bCh[i] << "\t" << probR[i] << "\t" << probG[i] << "\t" << probB[i] << "\n"; 
     } 

     double entropyR = 0.0; 
     double entropyG = 0.0; 
     double entropyB = 0.0; 
     for (int i = 0; i < numBins; ++i) { 
      entropyR += probR[i]*log(probR[i]); 
      entropyG += probG[i]*log(probG[i]); 
      entropyB += probB[i]*log(probB[i]); 
     } 
     cout << frame_number << "\t" << (-1.0)*(entropyR + entropyG + entropyB) << endl; 
    } 
    c = cvWaitKey(1000/fps); 
    if (c == 27) 
     break; 
} 
//cvReleaseImage(&img); 
cvReleaseCapture(&capture); 
cvDestroyWindow("Video"); 
return 0; 
} 

OUTPUT：

. 
. 
254  -1.#IND 
255  -1.#IND 
256  -1.#IND 
257  -1.#IND 
258  5.5686 
. 
. 

我第一次發現圖像熵，出來是正確的。 但近80％的視頻幀entropies出來是-1.#IND。

這是視頻.... download

可能是什麼回事？

Answer 1

可能是prob[i] = 0對於某些i，因此您計算的是log(0)這是未定義的。爲了解決這個問題，你簡單地放棄這種「可能性」：

for (int i = 0; i < numBins; ++i) { 
    if (prob[i]) 
     entropy += prob[i]*log(prob[i]); 
} 

爲你找到關於垃圾桶255 0值的其他錯誤，那是因爲你所指定的範圍內。 OpenCV將相關函數的範圍視爲[開始，結束]，因此指定範圍[0,255）將忽略255的結束值。所需的是保留0和255，因此：

float range[] = {0, numBins};