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源代码在opencv库里面的cvboost.cpp文件里面，该宏的总体思路是通过定义带参数的宏，把参数传递给宏内部的函数，然后进行一系列的计算，并最终根据一定的算法找到合适的阈值。具体解析如下：
#define ICV_DEF_FIND_STUMP_THRESHOLD( suffix, type, error ) static int icvFindStumpThreshold_##suffix( uchar* data, size_t datastep, uchar* wdata, size_t wstep, uchar* ydata, size_t ystep, uchar* idxdata, size_t idxstep, int num, float* lerror, float* rerror, float* threshold, float* left, float* right, float* sumw, float* sumwy, float* sumwyy ) { int found = 0; float wyl = 0.0F; float wl = 0.0F; float wyyl = 0.0F; float wyr = 0.0F; float wr = 0.0F; float curleft = 0.0F; float curright = 0.0F; float* prevval = NULL; float* curval = NULL; float curlerror = 0.0F; float currerror = 0.0F; int i = 0; int idx = 0; if( *sumw == FLT_MAX ) { /* calculate sums */ float *y = NULL; float *w = NULL; float wy = 0.0F; *sumw = 0.0F; *sumwy = 0.0F; *sumwyy = 0.0F; for( i = 0; i < num; i++ ) { idx = (int) ( *((type*) (idxdata + i*idxstep)) ); //根据样本的数据和step确定其索引idx w = (float*) (wdata + idx * wstep); *sumw += *w; //计算权重和 y = (float*) (ydata + idx * ystep); wy = (*w) * (*y); //计算权重w和类别y的乘积和 *sumwy += wy; *sumwyy += wy * (*y); } } for( i = 0; i < num; i++ ) { idx = (int) ( *((type*) (idxdata + i*idxstep)) ); curval = (float*) (data + idx * datastep); /* for debug purpose */ if( i > 0 ) assert( (*prevval) <= (*curval) ); wyr = *sumwy - wyl; //计算右边的权重与类别的乘积和 wr = *sumw - wl; //计算右边的权重和 if( wl > 0.0 ) curleft = wyl / wl; //计算左边不纯度 else curleft = 0.0F; if( wr > 0.0 ) curright = wyr / wr; //计算右边不纯度 else curright = 0.0F; error if( curlerror + currerror < (*lerror) + (*rerror) ) //如果当前的不纯度和小于原来的不纯度和 { (*lerror) = curlerror; (*rerror) = currerror; *threshold = *curval; if( i > 0 ) { *threshold = 0.5F * (*threshold + *prevval); } *left = curleft; *right = curright; found = 1; } do { wl += *((float*) (wdata + idx * wstep)); wyl += (*((float*) (wdata + idx * wstep))) * (*((float*) (ydata + idx * ystep))); wyyl += *((float*) (wdata + idx * wstep)) * (*((float*) (ydata + idx * ystep))) * (*((float*) (ydata + idx * ystep))); } while( (++i) < num && ( *((float*) (data + (idx = (int) ( *((type*) (idxdata + i*idxstep))) ) * datastep)) == *curval ) ); --i; prevval = curval; } /* for each value */ return found; ｝
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ICV_DEF_FIND_STUMP_THRESHOLD( suffix, type, error )
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原文地址：http://blog.csdn.net/ding977921830/article/details/46804875
