Thumtrack Length Issue when resizing window with Image on Horizontal fit - c++

Question

For Example: if my image width and height is 1600x2000 and client window width and height is 900x600.. now I want to fit the image horizontally. For that I will bring down the image width(1600) to window width(900) and also to maintain the original aspect ratio of the image i will also bring down the height of the image(2000) to 1125. for that I have used the below logic in FITHORIZONTAL Then I will use below wm_size code to set the scroll bar position and thumb length. Unfortunately the full image is not shown even though the thumb tracker has reached the end of the scroll bar.
switch(FitType)
{
case FITHORIZONTAL:
//find out whether resize percentage is decrease or increase
if(ActualImageWidth > WindowWidth) //resize decreasing
{
//find out the pecentage of decreased value
resizedPercent = WindowWidth/ActualImageWidth;
} else //resize increasing
{
//find out the pecentage of increased value
resizedPercent = ActualImageWidth/WindowWidth;
}
ResizedWidth = iWndwidth;
ResizedHeight = ActualImageHeight * resizedPercent;
break;
}
case WM_SIZE :
{
GetWindowRect(hWnd, &rect);
WndWidth = rect.right - rect.left;
WndHeight = rect.bottom - rect.top;
GetScrollInfo(hWnd, SB_VERT, &si);
int yMaxScroll = max((int)ResizedHeight - WndHeight, 0);
int yCurrentScroll = min(si.nPos, yMaxScroll);
si.cbSize = sizeof(si);
si.fMask = SIF_RANGE | SIF_PAGE | SIF_POS;
si.nMin = 0;
si.nMax = ResizedHeight;
si.nPage = WndHeight;
si.nPos = 0;
SetScrollInfo(hWnd, SB_VERT, &si, TRUE);
InvalidateRect(hWnd, &rect, true);
return 0;
}