Win32 绘制RGB三原色图案

以前看到三原色的图案，一直很好奇是如何画出来。后来终于搞清楚了，其实很简单，实际上就是RGB三个分量的"位与"运算。

下面给出Win32绘制三原色图案的例子，特此记录在此：

#include <windows.h>

LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);


int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int iCmdShow)
{
    static TCHAR szAppName[]=TEXT("RGB_SRCPAINT");
    HWND hWnd;
    MSG msg;
    WNDCLASS wc= {sizeof(WNDCLASS)};
    wc.style=CS_HREDRAW|CS_VREDRAW;
    wc.lpfnWndProc=WndProc;
    wc.cbClsExtra=0;
    wc.cbWndExtra=0;
    wc.hInstance=hInstance;
    wc.hIcon=LoadIcon(NULL,IDI_APPLICATION);
    wc.hCursor=LoadCursor(NULL,IDC_ARROW);
    wc.hbrBackground=(HBRUSH)GetStockObject(WHITE_BRUSH);
    wc.lpszMenuName=NULL;
    wc.lpszClassName=szAppName;
    if(!RegisterClass(&wc)) {
        MessageBox(NULL,TEXT("error"),szAppName,MB_ICONERROR|MB_OK);
        return 0;
    }
    hWnd=CreateWindow(szAppName,TEXT("RGB"),WS_OVERLAPPEDWINDOW,
                      320,120,500,500,NULL,NULL,hInstance,NULL);

    //
    ShowWindow(hWnd,iCmdShow);
    UpdateWindow(hWnd);
    while(GetMessage(&msg,NULL,0,0)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return msg.wParam;
}
//
void Circle(HDC dc,int ox,int oy,int r)
{
    Ellipse(dc,ox-r,oy-r,ox+r,oy+r);
}
//
LRESULT CALLBACK WndProc(HWND hWnd,UINT message,WPARAM wParam,LPARAM lParam)
{
    //
    HDC hdc,hMemDC;
    HBITMAP hBitmap;
    HBRUSH hbrush;
    RECT rc= {0,0,500,500};
    PAINTSTRUCT ps;
    int ox=250,oy=210,r=100;
    //
    switch (message) {
    case   WM_PAINT :
        hdc=BeginPaint(hWnd,&ps);
        //MemDC
        hMemDC = CreateCompatibleDC(hdc);
        hBitmap = CreateCompatibleBitmap(hdc,500,500);
        SelectObject(hMemDC,hBitmap);
        //ClearScreen with  Black
        hbrush = CreateSolidBrush(RGB(0, 0, 0));
        SelectObject(hMemDC,hbrush);
        FillRect(hdc,&rc,hbrush);
        //RED
        hbrush = CreateSolidBrush(RGB(255, 0, 0));
        SelectObject(hMemDC,hbrush);
        //Ellipse(hMemDC,0+200,0+200+30,100+200,100+200+30);
        Circle(hMemDC,ox,oy+0.8*r,r);
        BitBlt(hdc,0,0,500,500,hMemDC,0,0,SRCPAINT);
        //GREEN
        hbrush = CreateSolidBrush(RGB(0, 255, 0));
        SelectObject(hMemDC,hbrush);
        //Ellipse(hMemDC,0+200-26,0+200-15,100+200-26,100+200-15);
        Circle(hMemDC,ox-0.866*0.8*r,oy-0.5*0.8*r,r);
        BitBlt(hdc,0,0,500,500,hMemDC,0,0,SRCPAINT);
        //BLUE
        hbrush = CreateSolidBrush(RGB(0, 0, 255));
        SelectObject(hMemDC,hbrush);
        //Ellipse(hMemDC,0+200+26,0+200-15,100+200+26,100+200-15);
        Circle(hMemDC,ox+0.866*0.8*r,oy-0.5*0.8*r,r);
        BitBlt(hdc,0,0,500,500,hMemDC,0,0,SRCPAINT);
        //
        DeleteObject(hBitmap);
        DeleteDC( hMemDC );
        EndPaint (hWnd, &ps) ;

        break;
    case WM_DESTROY :
        PostQuitMessage(0);
        break ;
    }
    return DefWindowProc (hWnd, message, wParam, lParam) ;
}