使用 STM_SETIMAGE 之前在位图上设置透明度

Question

我有一个静态控件，我通过使用位图将 STM_IMAGE 发送到控件来设置图像。这工作正常，但我希望位图具有透明背景。我有以下代码：

case WM_PAINT:
{
    HBITMAP hbmBmp, hbmMask;
    BITMAP bm;
    PAINTSTRUCT ps;

    HDC hdc = BeginPaint(hWnd, &ps);
    HWND hCtrl = GetDlgItem(hWnd, ID_BUTTONNEWGAME);
    hbmBmp = LoadBitmap(GetModuleHandle(NULL), MAKEINTRESOURCE(IDB_NEWGAMEBUTTONBITMAP));
    GetObject(hbmBmp, sizeof(BITMAP), &bm);
    hbmMask = CreateBitmapMask(hbmBmp, RGB(0, 0, 0));
    HDC hDCMem = CreateCompatibleDC(hdc);
    HDC hDCMem2 = CreateCompatibleDC(hdc);
    HDC hdcResult = CreateCompatibleDC(hdc);

    SelectObject(hDCMem, hbmMask);
    BitBlt(hdc, 0, 0, bm.bmWidth, bm.bmHeight, hDCMem, 0, 0, SRCAND);

    SelectObject(hDCMem, hbmBmp);
    BitBlt(hdc, 0, 0, bm.bmWidth, bm.bmHeight, hDCMem, 0, 0, SRCPAINT);

    // At this point I can see the bitmap with a transparent background at (0,0)
    // The following code attempts to copy from hdc into a memory DCand to form a new bitmap 
    //that I use in the STM_SETIMAGE message

    HBITMAP newBitmap = CreateCompatibleBitmap(hdc, bm.bmWidth, bm.bmHeight); // create blank bitmap
    SelectObject(hdcResult, newBitmap); // store in memory DC
    BitBlt(hdcResult, 0, 0, bm.bmWidth, bm.bmHeight, hdc, 0, 0, SRCCOPY); // copy from hdc to memory DC

    // This line is just for checking that hdcResult contains the correct data
    // It copies back from the memory DC into hdc to the right of the original bitmap
    // I now see two bitmaps with transparent bitmaps next to each other as I expected
    BitBlt(hdc, bm.bmWidth, 0, bm.bmWidth, bm.bmHeight, hdcResult, 0, 0, SRCCOPY); 
    EndPaint(hWnd, &ps);

    // sending this does not set the bitmap on the static control
    // I do not see anything where the control should be
    SendMessage(hCtrl, STM_SETIMAGE, (WPARAM)IMAGE_BITMAP, (LPARAM)newBitmap);
}
break;

在下面的代码中使用 SS_BITMAP 样式创建静态控件：

case WM_CREATE:
{
    HWND newGameText = CreateWindowW(
        L"STATIC",
        L"",
        WS_VISIBLE | WS_CHILD | SS_BITMAP | SS_NOTIFY,  // Styles 
        150,         // x position 
        150,         // y position 
        74,        //  width
        24,        //  height
        hWnd,     // Parent window
        (HMENU)ID_BUTTONNEWGAME,
        (HINSTANCE)GetWindowLong(hWnd, GWL_HINSTANCE),
        NULL);      // Pointer not needed.
}
break;

我需要将位图复制到设备上下文中控件的特定位置（这似乎不合理）还是我在做一些完全不可能/愚蠢的事情？

Answer 1

我认为控制SS_BITMAP 并处理WM_PAINT 消息没有意义。并且发送STM_SETIMAGE（即更改显示的位图）以响应每个绘制请求（WM_PAINT 消息）是相当过分的，不是吗？完成后，您应该删除所有内容（您创建的 DC 和位图以及 STM_SETIMAGE 消息返回的值（之前传递给控件的位图）。

要么将控件设为SS_BITMAP 并使用STM_SETIMAGE，要么将其设为owner-drawn 并处理WM_DRAWITEM 消息。

您可能还想检查TransparentBlt() 函数。

 

---

 

我在这里添加了一些工作示例的代码。简单易实现，只需要编写很少的代码。所有者绘制的案例确实绘制了具有透明区域的位图。一切都是使用老式 GDI（不是 GDI+）函数完成的。

在本例中，我创建了一个包含三个静态控件的对话框，以不同的方式实现：

• IDC_IMG1 : SS_BITMAP 样式，图片设置在资源文件中
• IDC_IMG2 : SS_BITMAP 样式最初没有图像，图像设置带有 STM_SETIMAGE 消息
• IDC_IMG3 : SS_OWNERDRAW 样式，显示带有透明区域的位图

 

资源文件内容：

IDB_BITMAP1    BITMAP    "Image1.bmp"
.
.
// Dialog Items
CONTROL    IDB_BITMAP1,IDC_IMG1,"Static",SS_BITMAP,7,7,136,126,WS_EX_CLIENTEDGE
CONTROL    "",IDC_IMG2,"Static",SS_BITMAP,154,7,17,15,WS_EX_CLIENTEDGE
CONTROL    "",IDC_IMG3,"Static",SS_OWNERDRAW,301,7,136,123,WS_EX_CLIENTEDGE

源代码：

// Resources
HBITMAP hBitmap = NULL;
int bmpW, bmpH;

INT_PTR CALLBACK DlgProc(HWND hDlg, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch (uMsg)
    {
        case WM_INITDIALOG:
            if (!hBitmap) // Initialize resources if not initialized already
            {
                BITMAP bmp;
                hBitmap = LoadBitmap(hInst, MAKEINTRESOURCE(IDB_BITMAP1));
                GetObject(hBitmap, sizeof(bmp), &bmp);
                bmpW = bmp.bmWidth;
                bmpH = bmp.bmHeight;
            }
            // Set bitmap in IDC_IMG2
            SendDlgItemMessage(hDlg, IDC_IMG2, STM_SETIMAGE, IMAGE_BITMAP, (LPARAM)hBitmap);
            break;
        case WM_DRAWITEM:
            if (wParam==IDC_IMG3) // Draw transparent bitmap in IDC_IMG3
            {
                LPDRAWITEMSTRUCT lpDIS = (LPDRAWITEMSTRUCT)lParam;
                HDC hMem = CreateCompatibleDC(lpDIS->hDC);
                HGDIOBJ hOldBmp = SelectObject(hMem, hBitmap);
                TransparentBlt(lpDIS->hDC, 0, 0, bmpW, bmpH, hMem, 0, 0, bmpW, bmpH, RGB(255,255,255));
                SelectObject(hMem, hOldBmp);
                return TRUE;
            }
            break;
        case WM_COMMAND:
            if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL)
                EndDialog(hDlg, LOWORD(wParam));
            break;
    }
    return FALSE;
}

结果如下：