BitmapColorTranslate(HDC hdcBits, BITMAP* pbm, DWORD rgb)

gistfile1.txt

/*
 *  using the first pixel as the "transparent" color, make all pixels
 *  in the hdc that are equal to the "transparent" color the passed
 *  color.
 */
PRIV VOID  BitmapColorTranslate(HDC hdcBits, BITMAP* pbm, DWORD rgb)
{
    HDC     hdcMask;
    HBITMAP hbmMask, hbmT;
    HBRUSH  hbrT;
    BOOL    fMono;

    /*
     * is the bitmap mono, or the first pixel is already equal to the
     * passed color?  if so we have nothing to do.
     */

    fMono = pbm->bmPlanes == 1 && pbm->bmBitsPixel == 1;
    if (fMono || GetPixel(hdcBits, 0, 0) == rgb)
        return;

    // create a mask bitmap and associated DC

    if ((hbmMask = CreateBitmap(pbm->bmWidth, pbm->bmHeight, 1, 1, NULL)))
    {
        hdcMask = CreateCompatibleDC(hdcBits);

        // select the mask bitmap into the mono DC

        hbmT = SelectObject(hdcMask, hbmMask);

        // create the brush and select it into the bits DC

        hbrT = SelectObject(hdcBits, CreateSolidBrush(rgb));

        // do a color to mono bitblt to build the mask
        // generate 1's where the source is equal to the background is
        if (hdcMask) {
           SetBkColor(hdcBits, GetPixel(hdcBits, 0, 0));
           BitBlt(hdcMask, 0, 0, pbm->bmWidth, pbm->bmHeight, hdcBits, 0, 0, SRCCOPY);
        
           // where the mask is 1 lay down the brush, where it is 0 leave the desitnation
   
           SetBkColor(hdcBits, rgbWhite);
           SetTextColor(hdcBits, rgbBlack);
           BitBlt(hdcBits, 0, 0, pbm->bmWidth, pbm->bmHeight, hdcMask, 0, 0, DSPDxax);
   
           DeleteObject(SelectObject(hdcBits, hbrT));
           DeleteObject(SelectObject(hdcMask, hbmT));
   
           DeleteDC(hdcMask);
        }
    }
}