Click here to Skip to main content
13,357,438 members (66,296 online)
Click here to Skip to main content
Add your own
alternative version


54 bookmarked
Posted 3 Jun 2003

Buffered Canvas for Memory DC with Rotation, Clipping, Transparency

, 3 Jun 2003
Rate this:
Please Sign up or sign in to vote.
Code for buffering and rotating your drawing context.

Sample Image - demo1.jpg


I needed to rotate some drawing that I am doing in a program, but there is no rotate method in the DC for a window. So I wrote a canvas class that could do rotation and solve other problems too!

The buffer canvas class will store all your DC operations and do one copy to the screen.


  1. Solves flickering problems
  2. Ability to rotate text, drawings, and images
  3. Clips anything outside of its bounds
  4. Transparency mode for replacing background color with other window contents

Using the code

The class is called CBuffCanvas and has very few function calls to remember:


CBuffCanvas(CWnd *pWnd, CRect bounds, COLORREF bkColor, bool isTransparent);

Requires a pointer to the window, the bounding rectangle, a background color, and whether to be transparent

Drawing context

CDC* GetDC();

Returns the DC to the buffered canvas. Use this DC to do all of your drawing operations.


void Rotate(int degrees, CPoint origin); void Rotate(int degrees);

Rotates the drawing counter-clockwise from the origin (optional).

Copy to screen

void Draw(CDC* screen);

Takes a pointer to a drawing context and copies the buffered context over to the screen.

CBuffCanvas memCanvas(this, CRect(50,50,350,350), RGB(100,100,100), true);

// Get the DC from the buffer for drawing
CDC * pmemDC = memCanvas.GetDC();

// Do some drawing and text
CPen bluePen(PS_SOLID, 1, RGB(0,0,255));
pmemDC->TextOut(130,150, "Buffer Canvas Demo");

// Rotate the canvas 30 degrees counter-clockwise

// Call the draw function to copy the buffered canvas to the screen

Note that there may be performance issues to consider, especially when using the transparent mode. Don't try to draw large areas if you don't want flickering. Also, try doing the rotation in another part of your program than the OnPaint function.

Points of interest

I got the transparent draw down using BitBlt's. Also the bit by bit rotation go by trigonometry back up to par.


This is my first go at it, so I hope that it works for everyone!


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here


About the Author

Kevin Spaeth
Web Developer
United States United States
I am currently working for the U.S. Peace Corps in the Kingdom of Tonga. I teach C++ at the Tongan Insitute of Higher Education. In my spare time, I go kayaking and snorkeling. Tonga is a very out of the way, non-tourist island in the South Pacific. If you need to just get away, I highly recommend you come here.
As for programming, I am currently working on MFC applications. I am always interested in more work if you like what I've done. Enjoy!


You may also be interested in...

Comments and Discussions

GeneralRe: a bit slowly Pin
billhao18-Jun-03 20:06
memberbillhao18-Jun-03 20:06 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Praise Praise    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

Permalink | Advertise | Privacy | Terms of Use | Mobile
Web03 | 2.8.180111.1 | Last Updated 4 Jun 2003
Article Copyright 2003 by Kevin Spaeth
Everything else Copyright © CodeProject, 1999-2018
Layout: fixed | fluid