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Transparent ellipse

How do you draw a transparent ellipse with GDI? I tried SetBkMode(), but I still get a white ellipse bk.

case WM_PAINT:
{
    hdc = BeginPaint(hwnd, &ps);
    SetBkMode(hdc, TRANSPARENT); // doesnt work
    Ellipse(hdc, 0,0,500,500);
    EndPaint(hwnd, &ps);
    break;
}
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1 answer

Adopted from Fill an ellipse in C ++ :

An ellipse is described with the current pen and filled with the current brush .

Therefore, you need to set a transparent brush. To do this, use GetStockObject(HOLLOW_BRUSH)to obtain it and SelectObject()to activate it for a given device context. So your code could be like this:

case WM_PAINT:
{
    hdc = BeginPaint(hwnd, &ps);
    SelectObject(hdc, GetStockObject(HOLLOW_BRUSH));
    Ellipse(hdc, 0,0,500,500);
    EndPaint(hwnd, &ps);
    break;
}
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