[代码片段]OSTU算法

 用在片上系统上的

//OSTU求图像的阈值
u8 otsuThreshold(u8 **img, u16 height, u16 width)
{
//    int width = frame->width;
//    int height = frame->height;
    u16 pixelCount[256];
    float pixelPro[256];
    u16 i, j, pixelSum = width * height, threshold = 0;
    //遍历灰度级[0,255]
    float w0, w1, u0tmp, u1tmp, u0, u1, u, deltaTmp, deltaMax = 0;
    //u8* data = (uchar*)frame->imageData;

    for(i = 0; i < 256; i++)
    {
        pixelCount[i] = 0;
        pixelPro[i] = 0;
    }

    //统计灰度级中每个像素在整幅图像中的个数
    for(i = 0; i < height; i++)
    {
        for(j = 0;j < width;j++)
        {
            pixelCount[ img[i][j] ]++;
        }
    }
    
    //计算每个像素在整幅图像中的比例
    for(i = 0; i < 256; i++)
    {
        pixelPro[i] = (float)pixelCount[i] / pixelSum;
    }

    for(i = 0; i < 256; i++)
    {
        w0 = w1 = u0tmp = u1tmp = u0 = u1 = u = deltaTmp = 0;
        for(j = 0; j < 256; j++)
        {
            if(j <= i)   //背景部分
            {
                w0 += pixelPro[j];
                u0tmp += j * pixelPro[j];
            }
            else   //前景部分
            {
                w1 += pixelPro[j];
                u1tmp += j * pixelPro[j];
            }
        }
        u0 = u0tmp / w0;
        u1 = u1tmp / w1;
        u = u0tmp + u1tmp;
        deltaTmp = w0 * pow((u0 - u), 2) + w1 * pow((u1 - u), 2);
        if(deltaTmp > deltaMax)
        {
            deltaMax = deltaTmp;
            threshold = i;
        }
    }

    return threshold;
}