Solved

Bitmap Rotation

Posted on 1997-05-12
3
402 Views
Last Modified: 2010-04-06
how do I rotate the bitmap in a standard TBitmap say 90 degrees left or right
0
Comment
Question by:elessar
[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
  • 2
3 Comments
 
LVL 4

Accepted Solution

by:
erajoj earned 50 total points
ID: 1336157
I had no clue whatsoever howto rotate a bitmap fast...
...so I had to find out.
This code is fast(!/?). And it can rotate a TImage at ANY
angle.
Set the arbangle real to what you want and the rest will be done
for you:

procedure TMainForm.Image1DblClick(Sender: TObject);
var
  points      : array[0..3] of TPoint;
  bmp         : TBitmap; { temporary storage }
  index       : Integer;
  minx, miny  : Integer;
  maxx, maxy  : Integer;
  arbangle, r : Real;

  function min(a, b: Integer): Integer;
  begin
    if a<b then result := a else result := b;
  end;

  function max(a, b: Integer): Integer;
  begin
    if a>b then result := a else result := b;
  end;

begin
  arbangle := 5; { arbitrary angle, can be any angle }
  if sender is TImage then with (sender as TImage) do { Is it a TImage? }
  if not picture.bitmap.empty then begin              { Is it a bitmap? }
    bmp := TBitmap.Create;
    r := Math.Degtorad(arbangle);
    { Some lame maths }
    points[0].x := round(width-(cos(r)*width-sin(r)*height));
    points[0].y := round(height-(sin(r)*width+cos(r)*height));
    points[1].x := round(width+sin(r)*height);
    points[1].y := round(height-cos(r)*height);
    points[2].x := round(width-cos(r)*width);
    points[2].y := round(height-sin(r)*width);
    points[3].x := Width;
    points[3].y := Height;
    { Remove negative coordinates }
    minx := min(points[0].x, min(points[1].x, min(points[2].x, points[3].x)));
    miny := min(points[0].y, min(points[1].y, min(points[2].y, points[3].y)));
    for index := 0 to 3 do begin
      dec(points[index].x, minx);
      dec(points[index].y, miny);
    end;
    maxx := max(points[0].x, max(points[1].x, max(points[2].x, points[3].x)));
    maxy := max(points[0].y, max(points[1].y, max(points[2].y, points[3].y)));
    { Set size }
    bmp.width  := maxx;
    bmp.Height := maxy;
    { Here's the magic }
    if not PlgBlt(
      bmp.canvas.handle, // handle of destination device context
      points,               // vertices of destination parallelogram
      canvas.handle,       // handle of source device context
      0,                // x-coord. of upper-left corner of source rect.
      0,                // y-coord. of upper-left corner of source rect.
      Width,             // width of source rectangle
      Height,             // height of source rectangle
      0,                 // handle of bitmask
      0,                 // x-coord. of upper-left corner of bitmask rect.
      0                   // y-coord. of upper-left corner of bitmask rect.
     ) then { errorhandling stuff };
     { Could possibly have been done in a better way }
     picture.bitmap.Width  := bmp.Width;
     picture.bitmap.Height := bmp.Height;
     canvas.draw(0, 0, bmp);
     bmp.Free;
  end;

end;

Hope you can use it!

/// John

0
 

Author Comment

by:elessar
ID: 1336158
exactly what I was looking for ta! - since I have also posted this question on newsgroups and some people have requested that if I get any replies could I forward them... any objections if I pass this code around?
0
 
LVL 4

Expert Comment

by:erajoj
ID: 1336159
No objections whatsoever!
Just make sure to mention that you got it via
the Experts Exchange.

/// John
0

Featured Post

Announcing the Most Valuable Experts of 2016

MVEs are more concerned with the satisfaction of those they help than with the considerable points they can earn. They are the types of people you feel privileged to call colleagues. Join us in honoring this amazing group of Experts.

Question has a verified solution.

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

Have you ever had your Delphi form/application just hanging while waiting for data to load? This is the article to read if you want to learn some things about adding threads for data loading in the background. First, I'll setup a general applica…
Introduction I have seen many questions in this Delphi topic area where queries in threads are needed or suggested. I know bumped into a similar need. This article will address some of the concepts when dealing with a multithreaded delphi database…
This video Micro Tutorial shows how to password-protect PDF files with free software. Many software products can do this, such as Adobe Acrobat (but not Adobe Reader), Nuance PaperPort, and Nuance Power PDF, but they are not free products. This vide…
There's a multitude of different network monitoring solutions out there, and you're probably wondering what makes NetCrunch so special. It's completely agentless, but does let you create an agent, if you desire. It offers powerful scalability …

729 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