Gdiplus 位图没有 Alpha 通道

Question

我正在尝试通过 BITMAPINFO（缩短的代码示例）创建 Gdiplus::Bitmap：

    BITMAPINFO bmi;
    HDC hdc;
    void* pvBits;

    ZeroMemory(&bmi, sizeof(BITMAPINFO));
    bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    bmi.bmiHeader.biWidth = some_width;
    bmi.bmiHeader.biHeight = some_height;
    bmi.bmiHeader.biPlanes = 1;
    bmi.bmiHeader.biBitCount = 24;
    bmi.bmiHeader.biCompression = BI_RGB;
    bmi.bmiHeader.biSizeImage = ((((bmi.bmiHeader.biWidth * bmi.bmiHeader.biBitCount) + 31) & ~31) >> 3) * bmi.bmiHeader.biHeight;

    HBITMAP hBM = CreateDIBSection(hDC, &bmi, DIB_RGB_COLORS, &pvBits, NULL, 0x0);
    FillMemory(pvBits, bmi.bmiHeader.biSizeImage, 255);

    HGDIOBJ oldObj = SelectObject(hDC, hBM);
    ReleaseDC(NULL, hDC);

    GdiFlush();

    GdiPlusBitmap* bitmap = new Gdiplus::Bitmap(&bmi, pvBits);

我的问题是创建的位图没有 alpha 通道 (PixelFormat24bppRGB)。我错过了什么？

Answer 1

bmi.bmiHeader.biBitCount = 32;
hDC = CreateCompatibleDC(someOtherDc);

你可以看一个例子here

Gdiplus 位图没有 Alpha 通道

Gdiplus Bitmap has no Alpha Channel

c++

gdi+

bitmap