如何从元素中卸载图片 [英] how can I unload a picture from an element

问题描述

如何使用 SendMessage 从元素中卸载图片我试图这样做:

how can I unload a picture from an element using SendMessage I tried to do this:

SendMessage(hWnd, BM_SETIMAGE, IMAGE_BITMAP, 0);

但没有帮助

HBITMAP mLoadImg(const WCHAR* szFilename)
{
    HBITMAP result = NULL;



    Gdiplus::Bitmap* bitmap = new Gdiplus::Bitmap(szFilename, false);
    bitmap->GetHBITMAP(NULL, &result);
    delete bitmap;
    return result;
}


void displayImage(HBITMAP mBmp, HWND mHwnd)
{
    RECT myRect;
    BITMAP bm;
    HDC screenDC, memDC;
    HBITMAP oldBmp;
    BLENDFUNCTION bf;



    GetObject(mBmp, sizeof(bm), &bm);



    bf.BlendOp = AC_SRC_OVER;
    bf.BlendFlags = 0;
    bf.SourceConstantAlpha = 0xff;



    bf.AlphaFormat = AC_SRC_ALPHA;



    screenDC = GetDC(mHwnd);
    GetClientRect(mHwnd, &myRect);



    if (mBmp == NULL)
        FillRect(screenDC, &myRect, (HBRUSH(CreateSolidBrush(RGB(50, 151, 151))))); 



    else
    {
        memDC = CreateCompatibleDC(screenDC);
        oldBmp = (HBITMAP)SelectObject(memDC, mBmp);
        AlphaBlend(screenDC, 0, 0, myRect.right, myRect.bottom, memDC, 0, 0, bm.bmWidth, bm.bmHeight, bf);
        SelectObject(memDC, oldBmp);
        DeleteDC(memDC);
        ReleaseDC(mHwnd, screenDC);

    }
}

放置图像的代码.我需要在将鼠标悬停在按钮上时更改图像，我决定这样做，以便删除旧图像并放置新图像

code for put image. I need to change the image when hovering over the button, I decided to do this so that the old image is removed and a new one is placed

推荐答案

正如@IInspectable 在 您的另一个问题，您只需要使用 BS_BITMAP 或 BS_ICON 窗口样式和 BM_SETIMAGE 消息.
以下代码片段对我有用.

As @IInspectable said in your another question, you just need to use the BS_BITMAP or BS_ICON window styles and BM_SETIMAGE message.
Following code snippet works for me.

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_CREATE:
        {
            HWND d = CreateWindow(L"BUTTON", NULL, WS_CHILD | WS_VISIBLE | BS_BITMAP | BS_NOTIFY,
                10, 10, 180, 180, hWnd, (HMENU)BUTTON_ID, hInst, 0);
            HBITMAP hbit = LoadBitmap(hInst, MAKEINTRESOURCE(IDB_BITMAP1));
            SendMessage(d, BM_SETIMAGE, (WPARAM)IMAGE_BITMAP, (LPARAM)hbit);
        }
        break;
    case WM_COMMAND:
        {
            switch (HIWORD(wParam))
            {
            case BN_SETFOCUS:
                SendMessage((HWND)lParam, BM_SETIMAGE, IMAGE_BITMAP, 0);
                break;
            default:
                return DefWindowProc(hWnd, message, wParam, lParam);
            }
        }
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hWnd, message, wParam, lParam);
    }
    return 0;
}

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