Smooth Sliding Graphics Object

Posted on 2003-02-22
Medium Priority
Last Modified: 2012-06-21
Using VC7, C++, no direct-x or open/gl. How can I smoothly slide an object(bitmap) across a bitmap background. I need to slide it slowly and smoothly in various directions. i.e. sliding a chess piece, etc.
Question by:_kp
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3

Author Comment

ID: 8000577
Forgot to mention, windows MFC platform.

Accepted Solution

imadjinn earned 200 total points
ID: 8000799
Here is a VERY useful class that I use for this task.  In your OnPaint (or wherever) create a CMemDC and pass the DC you created in to it.  Since it is dervied from CDC directly you can use it interchangeably with CPaintDC as well.

#ifndef _MEMDC_H_
#define _MEMDC_H_

// CMemDC - memory DC
// Author: Keith Rule
// Email:  keithr@europa.com
// Copyright 1996-2002, Keith Rule
// You may freely use or modify this code provided this
// Copyright is included in all derived versions.
// History - 10/3/97 Fixed scrolling bug.
//                   Added print support. - KR
//           11/3/99 Fixed most common complaint. Added
//                   background color fill. - KR
//           11/3/99 Added support for mapping modes other than
//                   MM_TEXT as suggested by Lee Sang Hun. - KR
//           02/11/02 Added support for CScrollView as supplied
//                    by Gary Kirkham. - KR
// This class implements a memory Device Context which allows
// flicker free drawing.

class CMemDC : public CDC {
     CBitmap          m_bitmap;          // Offscreen bitmap
     CBitmap*     m_oldBitmap;     // bitmap originally found in CMemDC
     CDC*          m_pDC;               // Saves CDC passed in constructor
     CRect          m_rect;               // Rectangle of drawing area.
     BOOL          m_bMemDC;          // TRUE if CDC really is a Memory DC.
     CMemDC(CDC* pDC, const CRect* pRect = NULL) : CDC()
          ASSERT(pDC != NULL);

          // Some initialization
          m_pDC = pDC;
          m_oldBitmap = NULL;
          m_bMemDC = !pDC->IsPrinting();

          // Get the rectangle to draw
          if (pRect == NULL) {
          } else {
               m_rect = *pRect;

          if (m_bMemDC) {
               // Create a Memory DC

               m_bitmap.CreateCompatibleBitmap(pDC, m_rect.Width(), m_rect.Height());
               m_oldBitmap = SelectObject(&m_bitmap);



               SetWindowOrg(m_rect.left, m_rect.top);
          } else {
               // Make a copy of the relevent parts of the current DC for printing
               m_bPrinting = pDC->m_bPrinting;
               m_hDC       = pDC->m_hDC;
               m_hAttribDC = pDC->m_hAttribDC;

          // Fill background
          FillSolidRect(m_rect, pDC->GetBkColor());
          if (m_bMemDC) {
               // Copy the offscreen bitmap onto the screen.
               m_pDC->BitBlt(m_rect.left, m_rect.top, m_rect.Width(), m_rect.Height(),
                    this, m_rect.left, m_rect.top, SRCCOPY);              
               //Swap back the original bitmap.
          } else {
               // All we need to do is replace the DC with an illegal value,
               // this keeps us from accidently deleting the handles associated with
               // the CDC that was passed to the constructor.              
               m_hDC = m_hAttribDC = NULL;
     // Allow usage as a pointer    
     CMemDC* operator->()
          return this;

     // Allow usage as a pointer    
     operator CMemDC*()
          return this;


Author Comment

ID: 8001254
Thanks for the info. Actually I'm already using that code. Guess you're right, it's pretty popular. ;) My question is more related to the animation...I have a small group of separate bitmaps that I want to blit seperately to an off screen empty buffer (a group of chips) using DrawTransparentBitmap(), then take that new image using DrawTransparentBitmap() to move it onto the screen and then draw/step/erase/etc. to allow moning them smoothly around the screen. Basically create a bitmap of all the little bitmaps in the collection, and move that one bitmap.

Author Comment

ID: 8001814
Update to previous question. I have it sort of working.
The problem now is I have a bitmap that I created with CreateCompatibleBitmap() and BltBlt'd into, in a CDC that I need to get a CBitmap reference to so I can prepare a mask for use with DrawTransparentBitmap(). How do I get/create the CBitmap I need from the CDC?

Featured Post

Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Article by: SunnyDark
This article's goal is to present you with an easy to use XML wrapper for C++ and also present some interesting techniques that you might use with MS C++. The reason I built this class is to ease the pain of using XML files with C++, since there is…
In days of old, returning something by value from a function in C++ was necessarily avoided because it would, invariably, involve one or even two copies of the object being created and potentially costly calls to a copy-constructor and destructor. A…
The viewer will learn how to user default arguments when defining functions. This method of defining functions will be contrasted with the non-default-argument of defining functions.
The viewer will be introduced to the member functions push_back and pop_back of the vector class. The video will teach the difference between the two as well as how to use each one along with its functionality.
Suggested Courses
Course of the Month14 days, 21 hours left to enroll

771 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question