[aeff]

saludos, como indica el título de este post mi duda es relacionada con esta API, lo que quiero lograr es opacidad entre dos Bitmaps, tengo una referencia implementada para C++ y cuando intento llevarla a Pascal usando Delphi no me funciona absolutamente nada, en realidad no tengo ni idea de que hace realmente con los objetos en juego, si alguien ya tiene alguna experiencia con esta API les pido que me den una mano, aquí les va la referencia quie tengo pero para C++,

void DrawAlphaBlend (HWND hWnd, HDC hdcwnd)
{
    HDC hdc;                          // handle of the DC we will create 
    BLENDFUNCTION bf;         // structure for alpha blending
    HBITMAP hbitmap;           // bitmap handle
    BITMAPINFO bmi;           // bitmap header
    VOID *pvBits;                // pointer to DIB section
    ULONG   ulWindowWidth, ulWindowHeight;      // window width/height
    ULONG   ulBitmapWidth, ulBitmapHeight;      // bitmap width/height
    RECT    rt;                   // used for getting window dimensions
    UINT32   x,y;              // stepping variables
    UCHAR ubAlpha;         // used for doing transparent gradient
UCHAR ubRed;        
    UCHAR ubGreen;
    UCHAR ubBlue;
    float fAlphaFactor;       // used to do premultiply

    // get window dimensions
    GetClientRect(hWnd, &rt);

    // calculate window width/height
    ulWindowWidth = rt.right - rt.left;  
    ulWindowHeight = rt.bottom - rt.top;  

    // make sure we have at least some window size
    if ((!ulWindowWidth) || (!ulWindowHeight))
        return;

    // divide the window into 3 horizontal areas
    ulWindowHeight = ulWindowHeight / 3;

    // create a DC for our bitmap -- the source DC for AlphaBlend 
    hdc = CreateCompatibleDC(hdcwnd);

    // zero the memory for the bitmap info
    ZeroMemory(&bmi, sizeof(BITMAPINFO));

    // setup bitmap info 
    // set the bitmap width and height to 60% of the width and height of each of the three horizontal areas. Later on, the blending will occur in the center of each of the three areas.
    bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    bmi.bmiHeader.biWidth = ulBitmapWidth = ulWindowWidth - (ulWindowWidth/5)*2;
    bmi.bmiHeader.biHeight = ulBitmapHeight = ulWindowHeight - (ulWindowHeight/5)*2;
    bmi.bmiHeader.biPlanes = 1;
    bmi.bmiHeader.biBitCount = 32;         // four 8-bit components
    bmi.bmiHeader.biCompression = BI_RGB;
    bmi.bmiHeader.biSizeImage = ulBitmapWidth * ulBitmapHeight * 4;

    // create our DIB section and select the bitmap into the dc
    hbitmap = CreateDIBSection(hdc, &bmi, DIB_RGB_COLORS, &pvBits, NULL, 0x0);
    SelectObject(hdc, hbitmap);

    // in top window area, constant alpha = 50%, but no source alpha
    // the color format for each pixel is 0xaarrggbb 
    // set all pixels to blue and set source alpha to zero
for (y = 0; y < ulBitmapHeight; y++)
for (x = 0; x < ulBitmapWidth; x++)
            ((UINT32 *)pvBits)[x + y * ulBitmapWidth] = 0x000000ff; 

    bf.BlendOp = AC_SRC_OVER;
    bf.BlendFlags = 0;
    bf.SourceConstantAlpha = 0x7f;  // half of 0xff = 50% transparency
    bf.AlphaFormat = 0;             // ignore source alpha channel

    if (!AlphaBlend(hdcwnd, ulWindowWidth/5, ulWindowHeight/5, 
                    ulBitmapWidth, ulBitmapHeight, 
                    hdc, 0, 0, ulBitmapWidth, ulBitmapHeight, bf))
        return;                     // alpha blend failed

    // in middle window area, constant alpha = 100% (disabled), source 
    // alpha is 0 in middle of bitmap and opaque in rest of bitmap 
for (y = 0; y < ulBitmapHeight; y++)
for (x = 0; x < ulBitmapWidth; x++)
            if ((x > (int)(ulBitmapWidth/5)) && (x < (ulBitmapWidth-ulBitmapWidth/5)) &&
                (y > (int)(ulBitmapHeight/5)) && (y < (ulBitmapHeight-ulBitmapHeight/5)))
                //in middle of bitmap: source alpha = 0 (transparent).
                // This means multiply each color component by 0x00.
                // Thus, after AlphaBlend, we have a, 0x00 * r, 
                // 0x00 * g,and 0x00 * b (which is 0x00000000)
                // for now, set all pixels to red
                ((UINT32 *)pvBits)[x + y * ulBitmapWidth] = 0x00ff0000; 
            else
                // in the rest of bitmap, source alpha = 0xff (opaque) 
                // and set all pixels to blue 
                ((UINT32 *)pvBits)[x + y * ulBitmapWidth] = 0xff0000ff; 
            endif;

    bf.BlendOp = AC_SRC_OVER;
    bf.BlendFlags = 0;
    bf.AlphaFormat = AC_SRC_ALPHA;  // use source alpha 
    bf.SourceConstantAlpha = 0xff;  // opaque (disable constant alpha)

    if (!AlphaBlend(hdcwnd, ulWindowWidth/5, ulWindowHeight/5+ulWindowHeight, ulBitmapWidth, ulBitmapHeight, hdc, 0, 0, ulBitmapWidth, ulBitmapHeight, bf))
        return;

    // bottom window area, use constant alpha = 75% and a changing
    // source alpha. Create a gradient effect using source alpha, and 
    // then fade it even more with constant alpha
    ubRed = 0x00;
    ubGreen = 0x00;
    ubBlue = 0xff;

for (y = 0; y < ulBitmapHeight; y++)
for (x = 0; x < ulBitmapWidth; x++)
        {
            // for a simple gradient, base the alpha value on the x 
            // value of the pixel 
            ubAlpha = (UCHAR)((float)x / (float)ulBitmapWidth * 255);
            //calculate the factor by which we multiply each component
            fAlphaFactor = (float)ubAlpha / (float)0xff; 
            // multiply each pixel by fAlphaFactor, so each component 
            // is less than or equal to the alpha value.
            ((UINT32 *)pvBits)[x + y * ulBitmapWidth] 
= (ubAlpha << 24) |                       //0xaa000000
                 ((UCHAR)(ubRed * fAlphaFactor) << 16) |  //0x00rr0000
((UCHAR)(ubGreen * fAlphaFactor) << 8) | //0x0000gg00
                 ((UCHAR)(ubBlue   * fAlphaFactor));      //0x000000bb
        }

    bf.BlendOp = AC_SRC_OVER;
    bf.BlendFlags = 0;
    bf.AlphaFormat = AC_SRC_ALPHA;   // use source alpha 
    bf.SourceConstantAlpha = 0xbf;   // use constant alpha, with 
                                     // 75% opaqueness

    AlphaBlend(hdcwnd, ulWindowWidth/5, 
               ulWindowHeight/5+2*ulWindowHeight, ulBitmapWidth, 
               ulBitmapHeight, hdc, 0, 0, ulBitmapWidth, 
               ulBitmapHeight, bf);

    // do cleanup
    DeleteObject(hbitmap);
    DeleteDC(hdc);

}

no tengo idea de como hacer funcionar esta API,

mil gracias de antemano colega,
espero que me puedan ayudar.

saludos!
aeff!