How to adjust/remove toolbar bounding rectangle
===

I have create my toolbar from the application, only 4 buttons and each button has the size of 80 by 64 pixels. The whole bitmap is 320 by 64.

    const int numButtons     = 4;
    const SIZE bitmapSize={80,64};
    HIMAGELIST hImageList = ImageList_Create(bitmapSize.cx, bitmapSize.cy, ILC_COLOR16 | ILC_MASK,numButtons, 0);

	
    HBITMAP hBitmap = LoadBitmap(hInst, MAKEINTRESOURCE(IDB_HOME));
    int iImageList = ImageList_AddMasked(hImageList, hBitmap, 0);
    SendMessage(hWndToolbar, TB_SETIMAGELIST, 0, (LPARAM)hImageList);

    TBBUTTON tbButtons[numButtons] = 
    {
        { 0, WM_BBBB1, TBSTATE_ENABLED, TBSTYLE_BUTTON, {0}, 0, 0},
        { 1, WM_BBBB2, TBSTATE_ENABLED, TBSTYLE_BUTTON, {0}, 0, 0},
        { 2, WM_BBBB3, TBSTATE_ENABLED, TBSTYLE_BUTTON, {0}, 0, 0},
        { 3, WM_BBBB4, TBSTATE_ENABLED, TBSTYLE_BUTTON, {0}, 0, 0}
    };

    // Add buttons.
    SendMessage(hWndToolbar, TB_BUTTONSTRUCTSIZE, (WPARAM)sizeof(TBBUTTON), 0);
    SendMessage(hWndToolbar, TB_ADDBUTTONS,(WPARAM)numButtons,(LPARAM)&tbButtons);
    SendMessage(hWndToolbar, TB_AUTOSIZE, 0, 0); 

    RECT _tbRect;
    SendMessage(hWndToolbar, TB_GETITEMRECT, 0, (LPARAM)&_tbRect);//0,0,87,70

It says the button has 87 in width and 70 in height, if my bitmap has its own bounding size and I don't want the control to add the bounding rectangle for toolbar, how can I do?

Thank you in advance!