[VC6] 在对话框上实现LOGO图片的渐变性切换效果

#include  " stdafx.h "
#include  < stdlib.h >
#include  " resource.h "

#define  ID_TIMER    1 

HINSTANCE hInst;

// global variables
BYTE *  lpCurBits;  // 当前显示用的
BYTE *  lpCacheBits;  // DIB临时存储区
// 三幅图片
BYTE *  lpBits[ 3 ];

// 信息头
BITMAPINFO bminfo;

// 图片所在矩形~
RECT rcImg;

// functions;
// 准备工作
void  DoPrepare(HWND hDlg);
LRESULT CALLBACK MyDlgProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam);
void  GetNextDIB( int  percent,  int  iSel);

int  APIENTRY WinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPSTR     lpCmdLine,
                      int        nCmdShow)
{
      //  TODO: Place code here.
    hInst  =  hInstance;
    DialogBoxParam(hInstance, MAKEINTRESOURCE(IDD_DIALOG1), NULL,
        (DLGPROC)MyDlgProc,  0 );
     return   0 ;
}

// 准备工作
void  DoPrepare(HWND hDlg)
{
    HBITMAP hBitmap;
    BITMAP bm;
     int  i, stride;    
    HDC hdc  =  GetDC(hDlg);
     // HDC hMemDC = CreateCompatibleDC(hdc);
     // ReleaseDC(hDlg, hdc);
    
     for (i = 0 ; i < 3 ; i ++ )
    {
        hBitmap  =  LoadBitmap(hInst, MAKEINTRESOURCE(IDB_BITMAP1  +  i));
         if (i  ==   0 )
        {
            GetObject(hBitmap,  sizeof (BITMAP),  & bm);
             // 图片所在客户区矩形
            rcImg.left  =   0 ;
            rcImg.top  =   0 ;
            rcImg.right  =  bm.bmWidth;
            rcImg.bottom  =  bm.bmHeight;
             // bminfo
             // 扫描行宽度（实际上图片大小一致）
            stride  =  (bm.bmWidth  *   24   +   31 )  /   32   *   4 ;
            bminfo.bmiHeader.biSize  =   sizeof (BITMAPINFOHEADER);
            bminfo.bmiHeader.biPlanes  =   1 ;
            bminfo.bmiHeader.biBitCount  =   24 ;
            bminfo.bmiHeader.biWidth  =  bm.bmWidth;
            bminfo.bmiHeader.biHeight  =  bm.bmHeight;
            bminfo.bmiHeader.biSizeImage  =  bm.bmHeight  *  stride;                
        }
         // lpBits[i] = (BYTE*)bm.bmBits;
        lpBits[i]  =  (BYTE * )malloc(bminfo.bmiHeader.biSizeImage);
        GetDIBits(hdc, hBitmap,  0 , bminfo.bmiHeader.biHeight, lpBits[i],  & bminfo, DIB_RGB_COLORS);

        DeleteObject(hBitmap);
    }
    ReleaseDC(hDlg, hdc);
     // DeleteDC(hMemDC);
     // 创建当前显示的DIB
    lpCurBits  =  (BYTE * )malloc(bminfo.bmiHeader.biSizeImage);
    memcpy(lpCurBits, lpBits[ 0 ], bminfo.bmiHeader.biSizeImage);
    lpCacheBits  =  (BYTE * )malloc(bminfo.bmiHeader.biSizeImage);
}

// the dlg's window procedure
LRESULT CALLBACK MyDlgProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
     static   int  iSel;
     // 当前百分比（当为100时，停止计时器）
     static   int  percent;
     switch  (message)
    {
         case  WM_INITDIALOG:
            {
                DoPrepare(hDlg);
                 // 默认选中第一个选项
                CheckDlgButton(hDlg, IDC_RADIO1, BST_CHECKED);
                iSel  =   0 ;
                percent  =   0 ;
                 return  TRUE;
            }
             break ;

         case  WM_COMMAND:
             switch (LOWORD(wParam))
            {
             case  IDOK:
             case  IDCANCEL:
                EndDialog(hDlg, LOWORD(wParam));                
                 break ;

             case  IDC_RADIO1:
             case  IDC_RADIO2:
             case  IDC_RADIO3:
                iSel  =  LOWORD(wParam)  -  IDC_RADIO1;
                percent  =   100 ;
                 // 把当前位图拷贝到缓冲区
                memcpy(lpCacheBits, lpCurBits, bminfo.bmiHeader.biSizeImage);
                SetTimer(hDlg, ID_TIMER,  20 , NULL);
                 break ;
            }
             break ;

         case  WM_PAINT:
            {
                PAINTSTRUCT ps;
                HDC hdc  =  BeginPaint(hDlg,  & ps);
                SetDIBitsToDevice(hdc, 
                     0 ,  0 , rcImg.right, rcImg.bottom,
                     0 ,  0 , 
                     0 , bminfo.bmiHeader.biHeight,
                    lpCurBits,
                     & bminfo,
                    DIB_RGB_COLORS);

                EndPaint(hDlg,  & ps);
            }
             break ;

         case  WM_TIMER:
            {
                 if (percent  <=   0 )
                {
                    KillTimer(hDlg, ID_TIMER);
                     return  TRUE;
                }
                percent  -=   5 ;
                GetNextDIB(percent, iSel);
                InvalidateRect(hDlg,  & rcImg, FALSE);
                 return  TRUE;
            }
             break ;

         case  WM_DESTROY:
            {
                 int  i;
                 for (i = 0 ; i < 3 ; i ++ )
                {
                    free(lpBits[i]);
                }
                free(lpCurBits);
                free(lpCacheBits);
            }
             return  TRUE;
    }
     return  FALSE;
}

// 已当前百分比进行混合图像
//                             100                  0
// percent: 混合百分比  当前图片|------------------>|目标图片
//                              |---percent-->| 
// destDIB: 目标DIB
void  GetNextDIB( int  percent,  int  iSel)
{
    unsigned  int  i;
     int  x1, x2;
     for (i = 0 ; i < bminfo.bmiHeader.biSizeImage; i ++ )
    {
        x1  =  lpCacheBits[i];
        x2  =  lpBits[iSel][i];
        lpCurBits[i]  =  (BYTE)((x1 * percent  +  x2 * ( 100 - percent) ) / 100 );
    }
}