新手求解答 error C2228: “.at”的左边必须有类/结构/联合 如何修改

//鼠标响应

static void mouseHandler(int event, int x,int y ,int flags,void* Load)

{

	IplImage *img0, *img1;

	const Mat* mat;

	load* tmpLoad=(load*)Load;

mat =(Mat *)tmpLoad->result3DImage;

img0 = (IplImage*)tmpLoad->img;

img1 = cvCloneImage(img0);

	CvFont font, font2,font3;

	uchar *ptr;

	char label[1000];

	char label2[1000];

	char label3[1000];

	cvInitFont (&font,CV_FONT_HERSHEY_PLAIN,1,1,0,1,1);

	cvInitFont (&font2,CV_FONT_HERSHEY_PLAIN,1,1,0,1,1);

	cvInitFont (&font3,CV_FONT_HERSHEY_PLAIN,1,1,0,1,1);

	if(event==CV_EVENT_LBUTTONDOWN)

	{

		ptr = cvPtr2D(img1, y,x,NULL);	//获取像素的灰度值

	 Vec3f point = mat.at<Vec3f>(y, x);

		sprintf(label, "Color:(%d, %d, %d)",ptr[0], ptr[1], ptr[2]);

		sprintf(label2, "Pixel:(%d, %d)", x, y);	//获取坐标点位置

		sprintf(label3, "3D:(%d, %d,%d)", x, y);	//获取坐标点位置

		

		cvRectangle(img1, cvPoint(x,y-12),cvPoint(x+180, y+20),

			CV_RGB(255,0,0),CV_FILLED, 8,0);

		cvPutText(img1,label,cvPoint(x,y),&font,CV_RGB(255,255,255) );

		cvPutText(img1,label2,cvPoint(x,y+20),&font2,CV_RGB(255,255,255) );

		cvPutText(img1,label3,cvPoint(x+20,y+20),&font3,CV_RGB(255,255,255) );

		cvShowImage("src",img1);

	}

}