/*############################################################################# * 文件名：histogram.c * 功能：  實現(xiàn)了指紋直方圖的操作 * modified by  PRTsinghua@hotmail.com#############################################################################*/#include <stdlib.h>#include <stdio.h>#include <string.h>#include "histogram.h"/* 直方圖可以快速計算位圖的一些信息，比如均值，方差等 */typedef struct iFvsHistogram_t{    FvsUint_t       ptable[256];    /* 8位圖像的直方圖 */    FvsInt_t        ncount;         /* 直方圖中的點數(shù) */    FvsInt_t        nmean;          /* -1 = 還沒有計算 */    FvsInt_t        nvariance;      /* -1 = 還沒有計算 */} iFvsHistogram_t;/******************************************************************************  * 功能：創(chuàng)建一個新的直方圖對象  * 參數(shù)：無  * 返回：失敗返回空，否則返回直方圖對象******************************************************************************/FvsHistogram_t HistogramCreate(){    iFvsHistogram_t* p = NULL;    p = (FvsHistogram_t)malloc(sizeof(iFvsHistogram_t));    if (p!=NULL)    {        /* 重置表 */        HistogramReset(p);    }    return (FvsHistogram_t)p;}/******************************************************************************  * 功能：破壞一個存在的直方圖對象  * 參數(shù)：histogram 直方圖對象指針  * 返回：錯誤編號******************************************************************************/void HistogramDestroy(FvsHistogram_t histogram){    iFvsHistogram_t* p = NULL;    if (histogram==NULL)        return;    p = histogram;    free(p);}/******************************************************************************  * 功能：重置一個存在的直方圖對象為0  * 參數(shù)：histogram 直方圖對象指針  * 返回：錯誤編號******************************************************************************/FvsError_t HistogramReset(FvsHistogram_t hist){    iFvsHistogram_t* histogram = (iFvsHistogram_t*)hist;    int i;    for (i = 0; i < 256; i++)        histogram->ptable[i] = 0;    histogram->ncount    = 0;    histogram->nmean     = -1;    histogram->nvariance = -1;    return FvsOK;}/******************************************************************************  * 功能：計算一個8-bit圖像的直方圖  * 參數(shù)：histogram 直方圖對象指針  *       image     圖像指針  * 返回：錯誤編號******************************************************************************/FvsError_t HistogramCompute(FvsHistogram_t hist, const FvsImage_t image){    iFvsHistogram_t* histogram = (iFvsHistogram_t*)hist;    FvsError_t nRet = FvsOK;    FvsInt_t w      = ImageGetWidth(image);    FvsInt_t h      = ImageGetHeight(image);    FvsInt_t pitch  = ImageGetPitch(image);    uint8_t* p      = ImageGetBuffer(image);    FvsInt_t x, y;    if (histogram==NULL || p==NULL)        return FvsMemory;    /* 首先重置直方圖 */    nRet = HistogramReset(hist);    /* 計算 */    if (nRet==FvsOK)    {        FvsInt_t pos;        for (y=0; y<h; y++)        {            pos = pitch*y;            for (x=0; x<w; x++)            {                histogram->ptable[p[pos++]]++;            }        }        histogram->ncount = w*h;    }    return nRet;}/******************************************************************************  * 功能：計算一個直方圖對象的均值  * 參數(shù)：histogram 直方圖對象指針  * 返回：均值******************************************************************************/FvsByte_t HistogramGetMean(const FvsHistogram_t hist){    iFvsHistogram_t* histogram = (iFvsHistogram_t*)hist;    FvsInt_t val, i;    val = histogram->nmean;    if (val==-1)    {        val = 0;        for (i = 1; i < 255; i++)            val += i*histogram->ptable[i];        i = histogram->ncount;        if (i>0)            val = val/i;        else            val = 0;        histogram->nmean = val;    }    return (uint8_t)val;}/******************************************************************************  * 功能：計算一個直方圖對象的方差  * 參數(shù)：histogram 直方圖對象指針  * 返回：方差******************************************************************************/FvsUint_t HistogramGetVariance(const FvsHistogram_t hist){    iFvsHistogram_t* histogram = (iFvsHistogram_t*)hist;    FvsInt_t val;    FvsInt_t i;    uint8_t mean;    val = histogram->nvariance;    if (val==-1)    {        /* 計算均值 */        mean = HistogramGetMean(hist);        val  = 0;        for (i = 0; i < 255; i++)            val += histogram->ptable[i]*(i - mean)*(i - mean);        i = histogram->ncount;        if (i>0)            val = val/i;        else            val = 0;        histogram->nvariance = val;    }    return (FvsUint_t)val;}