[WinAPI] Szybkie szukanie piksela o określonym kolorze...

#include <windows.h>
#include <windowsx.h>

LRESULT CALLBACK WindowProcedure( HWND, UINT, WPARAM, LPARAM );
void CaptureScreen( HWND );
void OnPaint( HWND hwnd );

char szClassName[] = "Screenshot";

HBITMAP hBitmap = NULL;
HBITMAP a = NULL;

int WINAPI WinMain( HINSTANCE hThisInstance, HINSTANCE hPrevInstance, LPSTR lpszArgument, int nFunsterStil )
{
    HWND hwnd;
    MSG messages;
    WNDCLASSEX wincl;
    HDC dc;
   
    wincl.hInstance = hThisInstance;
    wincl.lpszClassName = szClassName;
    wincl.lpfnWndProc = WindowProcedure;
    wincl.style = CS_DBLCLKS;
    wincl.cbSize = sizeof( WNDCLASSEX );
    wincl.hIcon = LoadIcon( NULL, IDI_APPLICATION );
    wincl.hIconSm = LoadIcon( NULL, IDI_APPLICATION );
    wincl.hCursor = LoadCursor( NULL, IDC_ARROW );
    wincl.lpszMenuName = NULL;
    wincl.cbClsExtra = 0;
    wincl.cbWndExtra = 0;
    wincl.hbrBackground =( HBRUSH ) COLOR_BACKGROUND;
    if( !RegisterClassEx( & wincl ) ) return 0;
   
    hwnd = CreateWindowEx( 0, szClassName, "Screenshot", WS_POPUP, CW_USEDEFAULT, CW_USEDEFAULT, 400, 300, HWND_DESKTOP, NULL, hThisInstance, NULL );
    CaptureScreen( hwnd );
    ShowWindow( hwnd, SW_MAXIMIZE );
    while( GetMessage( & messages, NULL, 0, 0 ) )
    {
        TranslateMessage( & messages );
        DispatchMessage( & messages );
    }
   
    return messages.wParam;
}

LRESULT CALLBACK WindowProcedure( HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam )
{
    switch( message )
    {
    case WM_PAINT:
        HANDLE_WM_PAINT( hwnd, wParam, lParam, OnPaint );
        break;
    case WM_DESTROY:
        PostQuitMessage( 0 );
        break;
        default:
        return DefWindowProc( hwnd, message, wParam, lParam );
    }
    return 0;
   
}

void OnPaint( HWND hwnd )
{
    HDC hBitmapdc, hWindowdc;
    HBITMAP hOld;
    PAINTSTRUCT ps;
    RECT rc;
    int nWid, nHt;
   
    if( a )
    {
        hWindowdc = BeginPaint( hwnd, & ps );
        hWindowdc = GetDC( hwnd );
        hBitmapdc = CreateCompatibleDC( hWindowdc );
        hOld = SelectBitmap( hBitmapdc, a );
        GetClientRect( hwnd, & rc );
        nWid = GetSystemMetrics( SM_CXSCREEN );
        nHt = GetSystemMetrics( SM_CYSCREEN );
        StretchBlt( hWindowdc, 0, 0, rc.right, rc.bottom, hBitmapdc, 0, 0, nWid, nHt, SRCCOPY );
        DeleteDC( hBitmapdc );
        EndPaint( hwnd, & ps );
    }
}

void CaptureScreen( HWND hParent )
{
    HDC hDesktopdc, hBitmapdc;
    int nWid, nHt;
    HBITMAP hOriginal;
    hDesktopdc = GetWindowDC( HWND_DESKTOP );
    if( hDesktopdc )
    {
        nWid = GetSystemMetrics( SM_CXSCREEN );
        nHt = GetSystemMetrics( SM_CYSCREEN );
        hBitmap = CreateCompatibleBitmap( hDesktopdc, nWid, nHt );
        hBitmapdc = CreateCompatibleDC( hDesktopdc );
        hOriginal =( HBITMAP ) SelectBitmap( hBitmapdc, hBitmap );
        BitBlt( hBitmapdc, 0, 0, nWid, nHt, hDesktopdc, 0, 0, SRCCOPY );
        DeleteDC( hBitmapdc );
        ReleaseDC( HWND_DESKTOP, hDesktopdc );
        UpdateWindow( hParent );
        a = hBitmap;
    }
}