Opencv画半透明圆形，并能推广到所有形状

void DrawTransCir(IplImage* img,int x,int y,int width,int height,CvScalar color,double alpha)
{
    IplImage * rec=cvCreateImage(cvSize(width,height),img->depth,img->nChannels);

    rec=(IplImage*)cvClone(img);

    cvCircle(rec, Point(x+width/2, y+height/2), 10, Scalar(255,0,0,0),-1);

    cvSetImageROI(img,cvRect(x,y,width,height));
    cvSetImageROI(rec,cvRect(x,y,width,height));
    cvAddWeighted(img,alpha,rec,1-alpha,0.0,img);
    cvResetImageROI(img);
    cvResetImageROI(rec);
    cvReleaseImage(&rec);

}

第一次写勿喷

此函数实现了在opencv里面画半透明圆形，通过设置兴趣点减少了运算了，能达到实时画图的效果。