Thumbnail Picture Control

Sample Image - ThumbNailCtrl.png

Introduction

Recently, I was asked to write a thumbnail control to preview a certain numbers of pictures from a database. At the beginning, I was just lazy and want to get one over the net. After a few days, unluckily, I still got nothing. With my boss pressure, I finally have to write it once. Thank you to my boss if you find this piece of code is useful.

Background

You are suggested to know a little bit about the use of custom control. I would recommend you to try the MFC Grid Control by Chris Maunder and his great articles at beginner level about "Creating Custom Controls".

Using the code

Although I have recommended you to have basic knowledge from previous articles, I will still provide step-by-step instructions to use the control.

Step 1: Create a Dialog resource with a custom control on it.
Type "CThumbNailControl" in class and "IDC_FRAME_THUMB" in ID

Step 2: Create a class and associate it to the preivous created dialog. Go to the header file of the class. Insert a include and a variable like below:

...
#include "ThumbNailControl.h"

class CThumbNailDlg : public CDialog
  {
  private:
    <code>CThumbNailControl	m_cThumbFrame</code>;
...

Step 3: And then go to the cpp file to add the line "DDX_Control(pDX, IDC_FRAME_THUMB, m_cThumbFrame);"

void CThumbNailDlg::DoDataExchange(CDataExchange* pDX)
{
  CDialog::DoDataExchange(pDX);
  //{{AFX_DATA_MAP(CThumbNailDlg)
  DDX_Text(pDX, IDC_MSG, m_sMsg);
  //}}AFX_DATA_MAP
  <code>DDX_Control(pDX, IDC_FRAME_THUMB, m_cThumbFrame);</code>
}

Step 4: Now, go to OnInitDialog. An initialization is required here. The two integers are the width and heigh of a thumbnail button. You must call the "m_cThumbFrame.InitializeVariables" once. The default size is width=100 & height=75.

BOOL CThumbNailDlg::OnInitDialog()
{
  CDialog::OnInitDialog();

...
  // TODO: Add extra initialization here
  m_cThumbFrame.InitializeVariables( 200, 150 );

  m_cThumbFrame.Add( "fish.bmp" );
  m_cThumbFrame.Add( "pinboard.bmp" );
  m_cThumbFrame.Add( "chess.bmp" );
  m_cThumbFrame.Add( "box.bmp" );
	
  return TRUE;  // return TRUE  unless you set the focus to a control
}

That's ALL.

Callback for L/R Mouse Clicks

Now, the control is ready to use. You only have to add a few more codes to response to the left and right mouse clicks (L/R MouseDown). In the header file of your dialog, add the following lines.

  afx_msg LRESULT OnTnbLClicked( WPARAM wParam, LPARAM lParam );
  afx_msg LRESULT OnTnbRClicked( WPARAM wParam, LPARAM lParam );

In the Message Map section of the dialog cpp file, add...

BEGIN_MESSAGE_MAP(CThumbNailDlg, CDialog)
  //{{AFX_MSG_MAP(CThumbNailDlg)
  ON_WM_SYSCOMMAND()
  ON_WM_PAINT()
  ON_WM_QUERYDRAGICON()
  //}}AFX_MSG_MAP
  ON_REGISTERED_MESSAGE( UWM_ON_TNB_LCLICKED, OnTnbLClicked )
  ON_REGISTERED_MESSAGE( UWM_ON_TNB_RCLICKED, OnTnbRClicked )
END_MESSAGE_MAP()

Now, you can add two functions to response to the 2 events.

  LRESULT CThumbNailDlg::OnTnbLClicked( WPARAM wParam, LPARAM /* lParam  */ )
  LRESULT CThumbNailDlg::OnTnbRClicked( WPARAM wParam, LPARAM /* lParam */ )

Some Known Issues

A smart reader like you may question for the supportted image formats. I am sorry that the current version could only support the bitmap file. Perhaps in the later version, I will add the code to support other formats. Interested readers could could refer to the article "Simple class for drawing pictures (jpg, tif, gif, etc...)" by Peter Hendrix or any other to integrate the codes together. I would be grateful if you spend the efforts to help me. ^_^

Another issue is about the calling of AfxMessageBox with mouse clicked action. You have to call ResetTrackFlag immediately after the popup of message box. I don't have time to deeply resolve it. Just write one more function to reset the flag. You may refer to and try modify the CThumbNailDlg::OnTnbRClicked in demo project to see the problem.

Comments

If you would like to give me comments and any suggestions, leave me a message or an email.

History

2002/10/25 Version 1.0 First relese.

License

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