Celebrate National IT Professionals Day with 3 months of free Premium Membership. Use Code ITDAY17

x
?
Solved

How to rotate an image in C++

Posted on 1999-01-25
3
Medium Priority
?
388 Views
Last Modified: 2008-03-10
How would one rotate an image in Visual C++, specify the point around which it is rotated, and as a bonus find out where in the newly rotated image a pixel from the origional image was? (Ex. find out where in the new image the bottom-leftmost pixel from the origional image is.)
0
Comment
Question by:Alec417
[X]
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 Comments
 
LVL 32

Expert Comment

by:jhance
ID: 1185125
Are you looking to do general purpose rotation or limited?  By limited, I mean orthogonal only perhaps.  If so, there are many shortcuts that speed things up by avoiding solving trigonometric (i.e. VERY slow) equations for each point.  If general purpose, you just perform a angular transformation on each point using the origin of the rotation as the base point.  Surely you covered this in grade-school mathematics....

BTW, this wouldn't be homework, would it???
0
 
LVL 10

Accepted Solution

by:
viktornet earned 240 total points
ID: 1185126
Here is a function that will do it...

double rad(double degree)
{
  return (degree * 3.1415 / 180);
}

int round(double num)
{
  return int(num + 0.5);
}

void RotateImage(Image* OrigImg, Image* NewImg, int Theta)
{
                  int CenterX, CenterY;
      double CosX, SinY;
      int x, y, nx, ny;
      NewImg->Width = OrigImg->Width;
      NewImg->Height = OrigImg->Height;
      CenterX = OrigImg->Width >> 1;
      CenterY = OrigImg->Height >> 1;
      CosX = cos(rad(Theta));
      SinY = sin(rad(Theta));
      for (int i = 0; i < OrigImg->Height; i++) {
            for (int j = 0; j < OrigImg->Width; j++) {
                  x = j - CenterX;
                  y = i - CenterY;
                  nx = CenterX + round(x*CosX - y*SinY);
                  ny = CenterY + round(x*SinY + Y*CosX);
                  NewImg->Pixels[j][i] = OrigImg->Pixels[nx][ny];
            }
      }
}

It should look something like this...

-Viktor
--Ivanov
0
 
LVL 23

Expert Comment

by:chensu
ID: 1185127
0

Featured Post

New benefit for Premium Members - Upgrade now!

Ready to get started with anonymous questions today? It's easy! Learn more.

Question has a verified solution.

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

Errors will happen. It is a fact of life for the programmer. How and when errors are detected have a great impact on quality and cost of a product. It is better to detect errors at compile time, when possible and practical. Errors that make their wa…
This article will show you some of the more useful Standard Template Library (STL) algorithms through the use of working examples.  You will learn about how these algorithms fit into the STL architecture, how they work with STL containers, and why t…
The viewer will be introduced to the technique of using vectors in C++. The video will cover how to define a vector, store values in the vector and retrieve data from the values stored in the vector.
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

730 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