for循环的一种加速方法

来源：互联网发布：ios编程软件编辑：程序博客网时间：2024/05/23 16:57

一、源码如下：

#include "stdafx.h"#include "cv.h"#include "highgui.h"#include <istream>using namespace cv;using namespace std; int _tmain(int argc, _TCHAR* argv[]){Mat srcImg = imread("D:\\Documents\\Desktop\\图像拼接测试图片\\11-over750.bmp", CV_LOAD_IMAGE_GRAYSCALE);Mat dstImg1, dstImg2;srcImg.copyTo(dstImg1);srcImg.copyTo(dstImg2);uchar *srcData = srcImg.data;uchar *dstData1 = dstImg1.data;uchar *dstData2 = dstImg2.data;int size = srcImg.cols * srcImg.rows;int threshold = 122;int i;double ts1 = ( double )getTickCount();for(i = 0; i < size; ++i){if(srcData[i] < threshold)dstData1[i] = 0;elsedstData1[i] = 255;}//idouble te1 = ( double )getTickCount();double tim1 = (te1 - ts1) * 1000.0 / getTickFrequency();double ts2 = ( double )getTickCount();i = 0;int size2 = size - 4;for(; i < size2; i += 4){if(srcData[i] < threshold)dstData2[i] = 0;elsedstData2[i] = 255;if(srcData[i + 1] < threshold)dstData2[i + 1] = 0;elsedstData2[i + 1] = 255;if(srcData[i + 2] < threshold)dstData2[i + 2] = 0;elsedstData2[i + 2] = 255;if(srcData[i + 3] < threshold)dstData2[i + 3] = 0;elsedstData2[i + 3] = 255;}//ifor(; i < size; ++i){if(srcData[i] < threshold)dstData2[i] = 0;elsedstData2[i] = 255;}//idouble te2 = ( double )getTickCount();double tim2 = (te2 - ts2) * 1000.0 / getTickFrequency();cout << "     one loop:" << tim1 << endl;cout << "one four loop:" << tim2 << endl;namedWindow("img1");namedWindow("img2");imshow("img1", dstImg1);imshow("img2", dstImg2);waitKey(0);return 0;}

时间对比：

1、Debug下时间：

2、Release下时间：

结论：几乎加速一倍。

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