最近刚好学习到梯度方面的知识，所以上网查找了下关于梯度化一副图片的opencv代码，参考代码出自http://www.cnblogs.com/gnuhpc/archive/2012/06/28/2568755.html

#include<stdio.h>
#include<cv.h>
#include<highgui.h>
#include<math.h>/*梯度化图片*/
int main()
{	IplImage* src=cvLoadImage("happycat.png",1);CvPoint center;//定义一个二维坐标的点int height = src ->height;int width  = src->width;double scale=-3;int row,col;double dx,dy,weight;uchar* ptr;center = cvPoint(src->width/2,src->height/2);cvNamedWindow("src",1);//显示原图cvShowImage("src",src);for(row=0;row<height;row++){		for(col=0;col<width;col++){dx=(double) (col-center.x)/center.x;dy=(double) (row-center.y)/center.y;weight = exp((dx*dx+dy*dy)*scale);/*可以使用opencv定义的宏来提取象素值,假设灰度图像image，存取其i行j列的象素可以这样：CV_IMAGE_ELEM(image, uchar, i, j)如果是彩色图像就是CV_IMAGE_ELEM(image, uchar, i, 3*j)CV_IMAGE_ELEM(image, uchar, i, 3*j+1)CV_IMAGE_ELEM(image, uchar, i, 3*j+2) */ptr=&CV_IMAGE_ELEM(src,uchar,row,col*3);ptr[0]=cvRound(ptr[0]*weight);//将浮点数转化为整数；ptr[1]=cvRound(ptr[1]*weight);ptr[2]=cvRound(ptr[2]*weight);}}cvSaveImage("grad.jpg",src,0);//保存图片cvNamedWindow("grad",1);cvShowImage("grad",src);//显示梯度化后的图片cvWaitKey(0);cvDestroyAllWindows();cvReleaseImage(&src);return 0;
}

效果如下：