// Calculate new X position, then adjust for workarea
   xNew = rParent.left + ((wParent - wChild) /2);
   if (xNew < rWorkArea.left) {
      xNew = rWorkArea.left;
   } else if ((xNew+wChild) > rWorkArea.right) {
      xNew = rWorkArea.right - wChild;
   }

   // Calculate new Y position, then adjust for workarea
   yNew = rParent.top  + ((hParent - hChild) /2);
   if (yNew < rWorkArea.top) {
      yNew = rWorkArea.top;
   } else if ((yNew+hChild) > rWorkArea.bottom) {
      yNew = rWorkArea.bottom - hChild;
   }

   // Set it, and return
   return SetWindowPos (hwndChild, NULL, xNew, yNew, 0, 0, SWP_NOSIZE |
          SWP_NOZORDER);
}

//----------------
//  BuildPngList
//----------------

BOOL BuildPngList (PTSTR pstrPathName, TCHAR **ppFileList, int *pFileCount,
     int *pFileIndex)
{
    static TCHAR              szImgPathName [MAX_PATH];
    static TCHAR              szImgFileName [MAX_PATH];
    static TCHAR              szImgFindName [MAX_PATH];

    WIN32_FIND_DATA           finddata;
    HANDLE                    hFind;

    static TCHAR              szTmp [MAX_PATH];
    BOOL                      bOk;
    int                       i, ii;
    int                       j, jj;

    // free previous file-list

    if (*ppFileList != NULL)
    {
        free (*ppFileList);
        *ppFileList = NULL;
    }

    // extract foldername, filename and search-name

    strcpy (szImgPathName, pstrPathName);
    strcpy (szImgFileName, strrchr (pstrPathName, '\\') + 1);

    strcpy (szImgFindName, szImgPathName);
    *(strrchr (szImgFindName, '\\') + 1) = '\0';
    strcat (szImgFindName, "*.png");

    // first cycle: count number of files in directory for memory allocation

    *pFileCount = 0;

    hFind = FindFirstFile(szImgFindName, &finddata);
    bOk = (hFind != (HANDLE) -1);

    while (bOk)
    {
        *pFileCount += 1;
        bOk = FindNextFile(hFind, &finddata);
    }
    FindClose(hFind);

    // allocation memory for file-list

    *ppFileList = (TCHAR *) malloc (*pFileCount * MAX_PATH);

    // second cycle: read directory and store filenames in file-list

    hFind = FindFirstFile(szImgFindName, &finddata);
    bOk = (hFind != (HANDLE) -1);

    i = 0;
    ii = 0;
    while (bOk)
    {
        strcpy (*ppFileList + ii, szImgPathName);
        strcpy (strrchr(*ppFileList + ii, '\\') + 1, finddata.cFileName);

        if (strcmp(pstrPathName, *ppFileList + ii) == 0)
            *pFileIndex = i;

        ii += MAX_PATH;
        i++;

        bOk = FindNextFile(hFind, &finddata);
    }
    FindClose(hFind);

    // finally we must sort the file-list

    for (i = 0; i < *pFileCount - 1; i++)
    {
        ii = i * MAX_PATH;
        for (j = i+1; j < *pFileCount; j++)
        {
            jj = j * MAX_PATH;
            if (strcmp (*ppFileList + ii, *ppFileList + jj) > 0)
            {
                strcpy (szTmp, *ppFileList + jj);
                strcpy (*ppFileList + jj, *ppFileList + ii);
                strcpy (*ppFileList + ii, szTmp);

                // check if this was the current image that we moved

                if (*pFileIndex == i)
                    *pFileIndex = j;
                else
                    if (*pFileIndex == j)
                        *pFileIndex = i;
            }
        }
    }

    return TRUE;
}

//----------------
//  SearchPngList
//----------------

BOOL SearchPngList (
        TCHAR *pFileList, int FileCount, int *pFileIndex,
        PTSTR pstrPrevName, PTSTR pstrNextName)
{
    if (FileCount > 0)
    {
        // get previous entry
        
        if (pstrPrevName != NULL)
        {
            if (*pFileIndex > 0)
                *pFileIndex -= 1;
            else
                *pFileIndex = FileCount - 1;
            
            strcpy (pstrPrevName, pFileList + (*pFileIndex * MAX_PATH));
        }
        
        // get next entry
        
        if (pstrNextName != NULL)
        {
            if (*pFileIndex < FileCount - 1)
                *pFileIndex += 1;
            else
                *pFileIndex = 0;
            
            strcpy (pstrNextName, pFileList + (*pFileIndex * MAX_PATH));
        }
        
        return TRUE;
    }
    else
    {
        return FALSE;
    }
}

//-----------------
//  LoadImageFile
//-----------------

BOOL LoadImageFile (HWND hwnd, PTSTR pstrPathName,
                png_byte **ppbImage, int *pxImgSize, int *pyImgSize,
                int *piChannels, png_color *pBkgColor)
{
    static TCHAR szTmp [MAX_PATH];

    // if there's an existing PNG, free the memory

    if (*ppbImage)
    {
        free (*ppbImage);
        *ppbImage = NULL;
    }

    // Load the entire PNG into memory

    SetCursor (LoadCursor (NULL, IDC_WAIT));
    ShowCursor (TRUE);

    PngLoadImage (pstrPathName, ppbImage, pxImgSize, pyImgSize, piChannels,
                  pBkgColor);

    ShowCursor (FALSE);
    SetCursor (LoadCursor (NULL, IDC_ARROW));

    if (*ppbImage != NULL)
    {
        sprintf (szTmp, "VisualPng - %s", strrchr(pstrPathName, '\\') + 1);
        SetWindowText (hwnd, szTmp);
    }
    else
    {
        MessageBox (hwnd, TEXT ("Error in loading the PNG image"),
            szProgName, MB_ICONEXCLAMATION | MB_OK);
        return FALSE;
    }

    return TRUE;
}

//----------------
//  DisplayImage
//----------------

BOOL DisplayImage (HWND hwnd, BYTE **ppDib,
        BYTE **ppDiData, int cxWinSize, int cyWinSize,
        BYTE *pbImage, int cxImgSize, int cyImgSize, int cImgChannels,
        BOOL bStretched)
{
    BYTE                       *pDib = *ppDib;
    BYTE                       *pDiData = *ppDiData;
    // BITMAPFILEHEADER        *pbmfh;
    BITMAPINFOHEADER           *pbmih;
    WORD                        wDIRowBytes;
    png_color                   bkgBlack = {0, 0, 0};
    png_color                   bkgGray  = {127, 127, 127};
    png_color                   bkgWhite = {255, 255, 255};

    // allocate memory for the Device Independant bitmap

    wDIRowBytes = (WORD) ((3 * cxWinSize + 3L) >> 2) << 2;

    if (pDib)
    {
        free (pDib);
        pDib = NULL;
    }

    if (!(pDib = (BYTE *) malloc (sizeof(BITMAPINFOHEADER) +
        wDIRowBytes * cyWinSize)))
    {
        MessageBox (hwnd, TEXT ("Error in displaying the PNG image"),
            szProgName, MB_ICONEXCLAMATION | MB_OK);
        *ppDib = pDib = NULL;
        return FALSE;
    }
    *ppDib = pDib;
    memset (pDib, 0, sizeof(BITMAPINFOHEADER));

    // initialize the dib-structure

    pbmih = (BITMAPINFOHEADER *) pDib;
    pbmih->biSize = sizeof(BITMAPINFOHEADER);
    pbmih->biWidth = cxWinSize;
    pbmih->biHeight = -((long) cyWinSize);
    pbmih->biPlanes = 1;
    pbmih->biBitCount = 24;
    pbmih->biCompression = 0;
    pDiData = pDib + sizeof(BITMAPINFOHEADER);
    *ppDiData = pDiData;

    // first fill bitmap with gray and image border

    InitBitmap (pDiData, cxWinSize, cyWinSize);

    // then fill bitmap with image

    if (pbImage)
    {
        FillBitmap (
            pDiData, cxWinSize, cyWinSize,
            pbImage, cxImgSize, cyImgSize, cImgChannels,
            bStretched);
    }

    return TRUE;
}

//--------------
//  InitBitmap
//--------------

BOOL InitBitmap (BYTE *pDiData, int cxWinSize, int cyWinSize)
{
    BYTE *dst;
    int x, y, col;

    // initialize the background with gray

    dst = pDiData;
    for (y = 0; y < cyWinSize; y++)
    {
        col = 0;
        for (x = 0; x < cxWinSize; x++)
        {
            // fill with GRAY
            *dst++ = 127;
            *dst++ = 127;
            *dst++ = 127;
            col += 3;
        }
        // rows start on 4 byte boundaries
        while ((col % 4) != 0)
        {
            dst++;
            col++;
        }
    }

    return TRUE;
}

//--------------
//  FillBitmap
//--------------

BOOL FillBitmap (
        BYTE *pDiData, int cxWinSize, int cyWinSize,
        BYTE *pbImage, int cxImgSize, int cyImgSize, int cImgChannels,
        BOOL bStretched)
{
    BYTE *pStretchedImage;
    BYTE *pImg;
    BYTE *src, *dst;
    BYTE r, g, b, a;
    const int cDIChannels = 3;
    WORD wImgRowBytes;
    WORD wDIRowBytes;
    int cxNewSize, cyNewSize;
    int cxImgPos, cyImgPos;
    int xImg, yImg;
    int xWin, yWin;
    int xOld, yOld;
    int xNew, yNew;

    if (bStretched)
    {
        cxNewSize = cxWinSize - 2 * MARGIN;
        cyNewSize = cyWinSize - 2 * MARGIN;

        // stretch the image to it's window determined size

        // the following two are the same, but the first has side-effects
        // because of rounding
//      if ((cyNewSize / cxNewSize) > (cyImgSize / cxImgSize))
        if ((cyNewSize * cxImgSize) > (cyImgSize * cxNewSize))
        {
            cyNewSize = cxNewSize * cyImgSize / cxImgSize;
            cxImgPos = MARGIN;
            cyImgPos = (cyWinSize - cyNewSize) / 2;
        }
        else
        {
            cxNewSize = cyNewSize * cxImgSize / cyImgSize;
            cyImgPos = MARGIN;
            cxImgPos = (cxWinSize - cxNewSize) / 2;
        }

        pStretchedImage = malloc (cImgChannels * cxNewSize * cyNewSize);
        pImg = pStretchedImage;

        for (yNew = 0; yNew < cyNewSize; yNew++)
        {
            yOld = yNew * cyImgSize / cyNewSize;
            for (xNew = 0; xNew < cxNewSize; xNew++)
            {
                xOld = xNew * cxImgSize / cxNewSize;

                r = *(pbImage + cImgChannels * ((yOld * cxImgSize) + xOld) + 0);
                g = *(pbImage + cImgChannels * ((yOld * cxImgSize) + xOld) + 1);
                b = *(pbImage + cImgChannels * ((yOld * cxImgSize) + xOld) + 2);
                *pImg++ = r;
                *pImg++ = g;
                *pImg++ = b;
                if (cImgChannels == 4)
                {
                    a = *(pbImage + cImgChannels * ((yOld * cxImgSize) + xOld)
                        + 3);
                    *pImg++ = a;
                }
            }
        }

        // calculate row-bytes

        wImgRowBytes = cImgChannels * cxNewSize;
        wDIRowBytes = (WORD) ((cDIChannels * cxWinSize + 3L) >> 2) << 2;

        // copy image to screen

        for (yImg = 0, yWin = cyImgPos; yImg < cyNewSize; yImg++, yWin++)
        {
            if (yWin >= cyWinSize - cyImgPos)
                break;
            src = pStretchedImage + yImg * wImgRowBytes;
            dst = pDiData + yWin * wDIRowBytes + cxImgPos * cDIChannels;

            for (xImg = 0, xWin = cxImgPos; xImg < cxNewSize; xImg++, xWin++)
            {
                if (xWin >= cxWinSize - cxImgPos)
                    break;
                r = *src++;
                g = *src++;
                b = *src++;
                *dst++ = b; /* note the reverse order */
                *dst++ = g;
                *dst++ = r;
                if (cImgChannels == 4)
                {
                    a = *src++;
                }
            }
        }

        // free memory

        if (pStretchedImage != NULL)
        {
            free (pStretchedImage);
            pStretchedImage = NULL;
        }

    }

    // process the image not-stretched

    else
    {
        // calculate the central position

        cxImgPos = (cxWinSize - cxImgSize) / 2;
        cyImgPos = (cyWinSize - cyImgSize) / 2;

        // check for image larger than window

        if (cxImgPos < MARGIN)
            cxImgPos = MARGIN;
        if (cyImgPos < MARGIN)
            cyImgPos = MARGIN;

        // calculate both row-bytes

        wImgRowBytes = cImgChannels * cxImgSize;
        wDIRowBytes = (WORD) ((cDIChannels * cxWinSize + 3L) >> 2) << 2;

        // copy image to screen

        for (yImg = 0, yWin = cyImgPos; yImg < cyImgSize; yImg++, yWin++)
        {
            if (yWin >= cyWinSize - MARGIN)
                break;
            src = pbImage + yImg * wImgRowBytes;
            dst = pDiData + yWin * wDIRowBytes + cxImgPos * cDIChannels;

            for (xImg = 0, xWin = cxImgPos; xImg < cxImgSize; xImg++, xWin++)
            {
                if (xWin >= cxWinSize - MARGIN)
                    break;
                r = *src++;
                g = *src++;
                b = *src++;
                *dst++ = b; /* note the reverse order */
                *dst++ = g;
                *dst++ = r;
                if (cImgChannels == 4)
                {
                    a = *src++;
                }
            }
        }
    }

    return TRUE;
}

//-----------------
//  end of source
//-----------------