Thumbnails viewer and image processing using GDI+ and MFC

// PreviewDlg.cpp : implementation file
//

#include "stdafx.h"
#include "ImageTool.h"
#include "PreviewDlg.h"
#include "MainFrm.h"
#include "ImageToolDoc.h"
#include "memdc.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

/////////////////////////////////////////////////////////////////////////////
// CPreviewDlg
CPreviewDlg::CPreviewDlg()
{
}

CPreviewDlg::~CPreviewDlg()
{
}

BEGIN_MESSAGE_MAP(CPreviewDlg, CDialog)
	//{{AFX_MSG_MAP(CPreviewDlg)
	ON_WM_CREATE()
	ON_WM_DRAWITEM()
	ON_WM_SIZE()
	ON_WM_CTLCOLOR()
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CPreviewDlg message handlers
int CPreviewDlg::OnCreate( LPCREATESTRUCT lpCreateStruct ) 
{
	if( CDialog::OnCreate( lpCreateStruct ) == -1 )
	{
		return -1;
	}
	
	CRect rect; GetClientRect( &rect );

	m_wndCanvas.Create( "Image Preview Canvas",
		                WS_VISIBLE | WS_CHILD | SS_OWNERDRAW,
						rect,
						this,
						80 );

	return 0;
}

void CPreviewDlg::OnDrawItem( int nIDCtl, LPDRAWITEMSTRUCT lpDrawItemStruct ) 
{
	if( lpDrawItemStruct->itemAction & ODA_DRAWENTIRE )
	{
		CMemDC *pMemDC = NULL;
		pMemDC = new CMemDC( lpDrawItemStruct->hDC );
		lpDrawItemStruct->hDC = pMemDC->m_hDC;

		CRect rect; GetClientRect( rect );
		HBRUSH hBrush = ::CreateSolidBrush( RGB(255, 255, 255) );
		
		::FillRect( lpDrawItemStruct->hDC, rect, hBrush );
		
		DeleteObject( hBrush );
		CImageToolDoc *pDoc = (CImageToolDoc*)((CMainFrame*)AfxGetMainWnd())->GetActiveDocument();
		
		if( pDoc->m_pSelectedImage != NULL )
		{
			Graphics graphics( lpDrawItemStruct->hDC );
			graphics.SetInterpolationMode(InterpolationModeHighQualityBicubic);
			graphics.DrawImage( pDoc->m_pSelectedImage,	
				                 Rect( lpDrawItemStruct->rcItem.left, 
									   lpDrawItemStruct->rcItem.top,
									   lpDrawItemStruct->rcItem.right - lpDrawItemStruct->rcItem.left,
									   lpDrawItemStruct->rcItem.bottom - lpDrawItemStruct->rcItem.top)); 
		}

		delete pMemDC;
	}
}

void CPreviewDlg::OnSize( UINT nType, int cx, int cy ) 
{
	CDialog::OnSize(nType, cx, cy);
	
	CRect rc; GetClientRect( rc );

	CMainFrame* pFrame = (CMainFrame*)AfxGetMainWnd();

	if( pFrame == NULL )
	{
		return;
	}

	CImageToolDoc* pDoc = (CImageToolDoc*)pFrame->GetActiveDocument();

	if( pDoc->m_pSelectedImage == NULL )
	{
		rc.SetRectEmpty();
		m_wndCanvas.MoveWindow( rc );
	}
	else
	{
		const int   nWidth    = rc.Width();
		const int   nHeight   = rc.Height();
		const float fRatio    = (float)nHeight/nWidth;
		const float fImgRatio = (float)pDoc->m_pSelectedImage->GetHeight()/pDoc->m_pSelectedImage->GetWidth();

		int XDest, YDest, nDestWidth, nDestHeight;
	
		if( fImgRatio > fRatio )
		{
			nDestWidth  = nHeight/fImgRatio;
			XDest       = (nWidth-nDestWidth)/2;
			YDest       = 0;
			nDestHeight = nHeight;
		}
		else
		{
			XDest       = 0;
			nDestWidth  = nWidth;
			nDestHeight = nWidth*fImgRatio;
			YDest       = (nHeight-nDestHeight)/2;
		}

		CRect rect(XDest, YDest, XDest+nDestWidth, YDest+nDestHeight);
		m_wndCanvas.MoveWindow( rect );
		m_wndCanvas.Invalidate();
	}
}

HBRUSH CPreviewDlg::OnCtlColor(CDC* pDC, CWnd* pWnd, UINT nCtlColor) 
{
	switch (nCtlColor) 
	{
	case CTLCOLOR_DLG:
		pDC->SetBkColor( RGB(255,255,255) );
		return (HBRUSH)GetStockObject( WHITE_BRUSH );
	default:
		return CDialog::OnCtlColor(pDC, pWnd, nCtlColor);
	}
}