MFC在绘制控件的时候出问题了，程序编译没报错，但是运行时报错了；但是我改了很长时间，不知道为什么imread会读取异常，sz2也不是空的啊，他就是当前工程文件夹里的图片啊，源码我贴下面了

#include "stdafx.h"
#include "NewButton.h"
#include "resource.h"
#include <opencv.hpp>

using namespace cv;

CNewButton::CNewButton()
{
    PICname = "";
    whetherback = false;
    m_FontSize = 94;
    m_FontName = "Yu Gothic UI Semibold";
}

CNewButton::~CNewButton()
{
}

//为按键按钮添加图片//
void CNewButton::DrawItem(LPDRAWITEMSTRUCT lpDrawItemStruct)
{
    CDC dc;
    CRect rect = lpDrawItemStruct->rcItem;//得到按键区域
    dc.Attach(lpDrawItemStruct->hDC);//得到绘制的设备环境CDC
    VERIFY(lpDrawItemStruct->CtlType == ODT_BUTTON);
    CPen penback(PS_SOLID, 1, RGB(30, 30, 30));
    dc.SelectObject(&penback);
    CBrush brubut(RGB(m_ButCol, m_ButCol, m_ButCol));
    dc.SelectObject(&brubut);
    dc.FillSolidRect(rect, RGB(m_BackCol, m_BackCol, m_BackCol));

    int num = 0;//0常态，1按下

    if (PICname != "")
    {
        CString picstr;
        CString A, C;
        Mat I;
        A = "ButtonBitmap/";
        C = ".PNG";
        picstr = A + PICname + C;


            std::string sz2 = CT2A(picstr.GetBuffer());

            I = imread( sz2, 1);

            CvvImage BC1;
            BC1.CopyOf(&P);

            CRect BitRect(0, 0, rect.right, rect.bottom);
            HDC hdc = dc.GetSafeHdc();
            BC1.DrawToHDC(hdc, BitRect);

        if (lpDrawItemStruct->itemState&ODS_SELECTED || whetherback)//当按下按钮时的处理
        {
            if (num)
            {
                num = 0;
            }
            else
            {
                num = 1;
            }

            CString backstr;
            A = "ButtonBitmap/";
            C = "b.png";
            backstr = A + PICname + C;


                std::string sz2 = CT2A(backstr.GetBuffer());
                Mat I = imread(sz2, 1);
                IplImage BP(I);

                CvvImage BC;
                BC.CopyOf(&BP);

                CRect BitRect(0, 0, rect.right, rect.bottom);
                HDC bhdc = dc.GetSafeHdc();
                BC.DrawToHDC(bhdc, BitRect);

        }
    }

    else{
        CString picstr;
        CString A, C;
        Mat I;
        A = "ButtonBitmap/";
        C = ".png";
        picstr = A + PICname + C;

            std::string  sz2 = CT2A(picstr.GetBuffer());
            I = imread(sz2, 1);

            IplImage *P;
            P = NULL;
            if (P)cvReleaseImage(&P);
            P = &IplImage(I);

            if (P == NULL)
            {

            }
            else
            {
                CvvImage C;
                C.CopyOf(P);
                CRect BitRect(0, 0, rect.right, rect.bottom);
                HDC hdc = dc.GetSafeHdc();
                C.DrawToHDC(hdc, BitRect);

            }
        }
}

BEGIN_MESSAGE_MAP(CNewButton, CButton)
//  ON_WM_MOUSEMOVE()
//  ON_WM_MOUSEHOVER()
//  ON_WM_MOUSELEAVE()
//  ON_WM_SETCURSOR()
END_MESSAGE_MAP()

sz2为空，函数imread异常

图片读取错误，检查图片的路径和格式。