如何发布BITMAP结构？

Question

After using a BITMAP struct to get a bitmap's information...

BITMAP bm;
HBITMAP hBitmap;
hBitmap = (HBITMAP)LoadImage(...);
GetObject(phBitmap, sizeof(BITMAP), &bm );

How am I supposed to release/free/dispose bm ?

Tried with delete and DeleteObject , none worked.

Answer 1

I'd say this

HBITMAP hBitmap;
hBitmap = (HBITMAP)LoadImage(...);

should better/nicer be

HANDLE handle = LoadImage(...);
if (NULL == handle)
{
  /*handle error */
}
else
{
  HBITMAP hbitmap = handle;

  {
    BITMAP bm = {0}; /* allocate and
            initialise bm on the stack. */

    GetObject(hbitmap, sizeof bm, &bm);

    /* Use bm here. */

   } /* Have bm be deallocated or at least
          be inaccessible from here on. */

   DeleteObject(hbitmap);
}

It is the handle that refers to the resource, which should be freed when not used anymore.

Answer 2

You would only need to use the operator delete if you had allocated the BITMAP with the operator new . (Modern, idiomatic C++ discourages manual memory management as well, but since you asked about this in your question, there you go).

A BITMAP is a struct of POD values dimensions and pixel data, and an HBITMAP can be a handle to a BITMAP if it is assigned as such. An HBITMAP does need to be released with a call to DeleteObject when it's no longer needed and no longer selected into a DC, even if it was allocated on the stack; a BITMAP on the stack will disappear when it goes out of scope.

There is a difference between the operator delete and the Windows GDI function DeleteObject . delete is a C++ keyword for removing objects from the heap; DeleteObject is an API call for freeing GDI resources.