[代码片段]OSTU算法

 1 //OSTU求图像的阈值
 2 u8 otsuThreshold(u8 **img, u16 height, u16 width)
 3 {
 4 //    int width = frame->width;
 5 //    int height = frame->height;
 6     u16 pixelCount[256];
 7     float pixelPro[256];
 8     u16 i, j, pixelSum = width * height, threshold = 0;
 9     //遍历灰度级[0,255]
10     float w0, w1, u0tmp, u1tmp, u0, u1, u, deltaTmp, deltaMax = 0;
11     //u8* data = (uchar*)frame->imageData;
12 
13     for(i = 0; i < 256; i++)
14     {
15         pixelCount[i] = 0;
16         pixelPro[i] = 0;
17     }
18 
19     //统计灰度级中每个像素在整幅图像中的个数
20     for(i = 0; i < height; i++)
21     {
22         for(j = 0;j < width;j++)
23         {
24             pixelCount[ img[i][j] ]++;
25         }
26     }
27     
28     //计算每个像素在整幅图像中的比例
29     for(i = 0; i < 256; i++)
30     {
31         pixelPro[i] = (float)pixelCount[i] / pixelSum;
32     }
33 
34     for(i = 0; i < 256; i++)
35     {
36         w0 = w1 = u0tmp = u1tmp = u0 = u1 = u = deltaTmp = 0;
37         for(j = 0; j < 256; j++)
38         {
39             if(j <= i)   //背景部分
40             {
41                 w0 += pixelPro[j];
42                 u0tmp += j * pixelPro[j];
43             }
44             else   //前景部分
45             {
46                 w1 += pixelPro[j];
47                 u1tmp += j * pixelPro[j];
48             }
49         }
50         u0 = u0tmp / w0;
51         u1 = u1tmp / w1;
52         u = u0tmp + u1tmp;
53         deltaTmp = w0 * pow((u0 - u), 2) + w1 * pow((u1 - u), 2);
54         if(deltaTmp > deltaMax)
55         {
56             deltaMax = deltaTmp;
57             threshold = i;
58         }
59     }
60 
61     return threshold;
62 }