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C-/C++-Quelltext

#include <windows.h>
#include <cmath>

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

const float PI = 4.0f * atanf( 1.0f );
const float HALF_PI = PI * .5f;

inline float Deg2Rad( float f ) 
{
    return f * ( PI / 180.0f );
}

int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE, PSTR, int )
{
    MSG msg;
    WNDCLASS wc;

    wc.style         = CS_HREDRAW | CS_VREDRAW;
    wc.cbClsExtra    = 0;
    wc.cbWndExtra    = 0;
    wc.hbrBackground = GetSysColorBrush( COLOR_BTNFACE );
    wc.hCursor       = LoadCursor( NULL, IDC_ARROW );
    wc.hIcon         = LoadIcon( NULL, IDI_APPLICATION );
    wc.hInstance     = hInstance;
    wc.lpfnWndProc   = WndProc;
    wc.lpszClassName = "RotateWndCls";
    wc.lpszMenuName  = NULL;

    RegisterClass( &wc );

    HWND hWnd = CreateWindow( "RotateWndCls", "Rotate", WS_OVERLAPPEDWINDOW, 0, 0, 800, 600, NULL, NULL, hInstance, NULL );
    ShowWindow( hWnd, SW_SHOW );
    UpdateWindow( hWnd );

    while ( GetMessage( &msg, NULL, 0, 0 ) )
    {
        TranslateMessage( &msg );
        DispatchMessage( &msg );
    }

    return ( int )msg.wParam;
}

LRESULT CALLBACK WndProc( HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam )
{
    static HBITMAP hBitmap;
    static int width, height;

    switch ( uMsg )
    {
    case WM_CREATE:
        hBitmap = ( HBITMAP )LoadImage( NULL, "bild.bmp", IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE );

        if ( !hBitmap )
        {
            MessageBox( hWnd, "Cannot load bild.bmp", "Error", MB_OK );
        }

        {
            BITMAP bmp;
            GetObject( hBitmap, sizeof( BITMAP ), &bmp );
            width = bmp.bmWidth;
            height = bmp.bmHeight;
        }
        break;

    case WM_CLOSE:
        PostQuitMessage( 0 );
        break;

    case WM_PAINT:
        {
            PAINTSTRUCT ps;
            HDC hDC, hMemDC;
            POINT dest[ 3 ];
            POINT p[ 2 ];
            POINT pos;
            float angle;
            float halfW, halfH;

            hDC = BeginPaint( hWnd, &ps );

            hMemDC = CreateCompatibleDC( hDC );
            SelectObject( hMemDC, hBitmap );

            angle = Deg2Rad( 92.0f );
            halfW = width / 2.0f;
            halfH = height / 2.0f;

            p[ 0 ].x = ( LONG )( cos( angle ) * halfW );
            p[ 0 ].y = ( LONG )( sin( angle ) * halfW );
            p[ 1 ].x = ( LONG )( cos( angle + HALF_PI ) * halfH );
            p[ 1 ].y = ( LONG )( sin( angle + HALF_PI ) * halfH );

            pos.x = 0;
            pos.y = 0;

            //! Rotationszeugs

            dest[ 0 ].x = ( LONG )( halfW + pos.x - p[ 0 ].x - p[ 1 ].x );
            dest[ 0 ].y = ( LONG )( halfH + pos.x - p[ 0 ].y - p[ 1 ].y );

            dest[ 1 ].x = ( LONG )( halfW + pos.x - p[ 1 ].x + p[ 0 ].x );
            dest[ 1 ].y = ( LONG )( halfH + pos.x - p[ 1 ].y + p[ 0 ].y );

            dest[ 2 ].x = ( LONG )( halfW + pos.x - p[ 0 ].x + p[ 1 ].x );
            dest[ 2 ].y = ( LONG )( halfH + pos.x - p[ 0 ].y + p[ 1 ].y );

            PlgBlt( hDC, dest, hMemDC, 0, 0, width, height, NULL, 0, 0 );
            
            DeleteDC( hMemDC );

            EndPaint( hWnd, &ps );
        }
        break;

    default:
        return DefWindowProc( hWnd, uMsg, wParam, lParam );
    }

    return 0;
}