Solved

Bitmap Rotation

Posted on 1997-05-12
3
400 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
  • 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

Suggested Solutions

Title # Comments Views Activity
delphi exception 7 68
Printing problem 2 102
tvirtualstringtree freeze when load too manny images 10 71
Why  'Host Connection unavailable/Socket Error #113 No route to host' 6 52
Creating an auto free TStringList The TStringList is a basic and frequently used object in Delphi. On many occasions, you may want to create a temporary list, process some items in the list and be done with the list. In such cases, you have to…
Hello everybody This Article will show you how to validate number with TEdit control, What's the TEdit control? TEdit is a standard Windows edit control on a form, it allows to user to write, read and copy/paste single line of text. Usua…
Although Jacob Bernoulli (1654-1705) has been credited as the creator of "Binomial Distribution Table", Gottfried Leibniz (1646-1716) did his dissertation on the subject in 1666; Leibniz you may recall is the co-inventor of "Calculus" and beat Isaac…

860 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