C / C++ / MFC

HRGN cMainSkin::ScanRegion(HBITMAP pBitmap, BYTE jTranspR, BYTE jTranspG, BYTE jTranspB)
{
    // bitmap width and height
    WORD wBmpWidth, wBmpHeight;

    // the final region and a temporary region
    HRGN hRgn, hTmpRgn;

    // 24bit pixels from the bitmap
    BYTE *pPixels = Get24BitPixels(pBitmap, &wBmpWidth, &wBmpHeight);
    
     if (!pPixels) 
          return NULL;

    // create our working region
    hRgn = CreateRectRgn(0, 0, wBmpWidth, wBmpHeight);
    
     if (!hRgn) 
     { 
          delete pPixels;
         
         return NULL;
    }

    // ---------------------------------------------------------
    // scan the bitmap
    // ---------------------------------------------------------
    DWORD p = 0;

    for (WORD y = 0; y < wBmpHeight; y++)
    {
         for (WORD x = 0; x < wBmpWidth; x++)
         {
              BYTE jRed   = pPixels[p+2];
              BYTE jGreen = pPixels[p+1];
              BYTE jBlue  = pPixels[p+0];

              if (jRed == jTranspR && jGreen == jTranspG && jBlue == jTranspB)
              {
                   // remove transparent color from region
                   hTmpRgn = CreateRectRgn(x,y,x+1,y+1);
                   CombineRgn(hRgn, hRgn, hTmpRgn, RGN_XOR);
                   DeleteObject(hTmpRgn);
              }

              // next pixel
              p += 3;
         }
    }

    // release pixels
    delete pPixels;

    // return the region
    return hRgn;
}

BYTE* Get24BitPixels(HBITMAP pBitmap, WORD *pwWidth, WORD *pwHeight)
{
    // a bitmap object just to get bitmap width and height
    BITMAP bmpBmp;

    // pointer to original bitmap info
    LPBITMAPINFO pbmiInfo;

    // bitmap info will hold the new 24bit bitmap info
    BITMAPINFO bmiInfo;

    // width and height of the bitmap
    WORD wBmpWidth, wBmpHeight;

    // ---------------------------------------------------------
    // get some info from the bitmap
    // ---------------------------------------------------------
    GetObject(pBitmap, sizeof(bmpBmp), &bmpBmp);
    pbmiInfo   = (LPBITMAPINFO) &bmpBmp;

    // get width and height
    wBmpWidth  = (WORD)pbmiInfo->bmiHeader.biWidth;
    wBmpWidth -= (wBmpWidth%4);                       // width is 4 byte boundary aligned.
    wBmpHeight = (WORD)pbmiInfo->bmiHeader.biHeight;

    // copy to caller width and height parms
    *pwWidth  = wBmpWidth;
    *pwHeight = wBmpHeight;
    // ---------------------------------------------------------

    // allocate width * height * 24bits pixels
    BYTE *pPixels = new BYTE[wBmpWidth*wBmpHeight*3];
    
     if (!pPixels) 
          return NULL;

    // get user desktop device context to get pixels from
    HDC hDC = GetWindowDC(NULL);

    // fill desired structure
    bmiInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    bmiInfo.bmiHeader.biWidth = wBmpWidth;
    bmiInfo.bmiHeader.biHeight = -wBmpHeight;
    bmiInfo.bmiHeader.biPlanes = 1;
    bmiInfo.bmiHeader.biBitCount = 24;
    bmiInfo.bmiHeader.biCompression = BI_RGB;
    bmiInfo.bmiHeader.biSizeImage = wBmpWidth * wBmpHeight * 3;
    bmiInfo.bmiHeader.biXPelsPerMeter = 0;
    bmiInfo.bmiHeader.biYPelsPerMeter = 0;
    bmiInfo.bmiHeader.biClrUsed = 0;
    bmiInfo.bmiHeader.biClrImportant = 0;

    // get pixels from the original bitmap converted to 24bits
    int iRes = GetDIBits(hDC, pBitmap, 0, wBmpHeight, (LPVOID)pPixels, &bmiInfo, DIB_RGB_COLORS);

    // release the device context
    ReleaseDC(NULL, hDC);

    // if failed, cancel the operation.
    if (!iRes)                                                              // The error is here, GetLastError gives me #87 INVALID_PARAM
    {
         delete pPixels;     
          
          return NULL;
    };

    // return the pixel array
    return pPixels;
}

void cMainSkin::SetButtonRegion(void)
{
    for (int i = 0; i < 7; i++)
         hButtonRgn[i] = ScanRegion(hButtonPartialBitmap[i], iMaskColor[0], 
                                           iMaskColor[1], iMaskColor[2]);

    
     SetWindowRgn(hwndMenu,     hButtonRgn[0], TRUE);
    SetWindowRgn(hwndMinimize, hButtonRgn[1], TRUE);
    SetWindowRgn(hwndClose,    hButtonRgn[2], TRUE);
    SetWindowRgn(hwndView,     hButtonRgn[3], TRUE);
    SetWindowRgn(hwndAdd,      hButtonRgn[4], TRUE);
    SetWindowRgn(hwndFind,     hButtonRgn[5], TRUE);
    SetWindowRgn(hwndExternal, hButtonRgn[6], TRUE);

    for (i = 0; i < 7; i++)
         DeleteObject(hButtonRgn[i]);
}