Mega Code Archive
How to flip a bitmap image
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Question:
Is there a RTL or API function to flip a bitmap image?
Answer:
You can use the Windows function StrechBlt() to help you with this. Some older versions of Windows (Windows 3.1, Windows 95) had problems with the graphic card drivers for these functions.
I myself had a Diamond Stealth (or was it a Diamond Speedstar?) where this Windows function was not implemented properly in the Windows 95 driver. There is another Win API function for it.. for device independant bitmaps - it is called StretchDIBits(), but StretchBlt() is faster.
And nowadays (June 2004), all graphic cards should be supported properly.
type
TMirror = (mtHorizontal, mtVertical, mtBoth );
procedure Mirror(Picture: TPicture; MirrorType: TMirror);
var
MemBmp: Graphics.TBitmap;
Dest: TRect;
begin { Mirror }
if Assigned(Picture.Graphic) then
begin
MemBmp := Graphics.TBitmap.Create;
try
MemBmp.PixelFormat := pf24bit;
MemBmp.HandleType := bmDIB;
MemBmp.Width := Self.Picture.Graphic.Width;
MemBmp.Height := Self.Picture.Height;
MemBmp.Canvas.Draw(0, 0, Picture.Graphic);
case MirrorType of
mtHorizontal:
begin
//SpiegelnVertikal(MemBmp);
//SpiegelnHorizontal(MemBmp);
Dest.Left := MemBmp.Width;
Dest.Top := 0;
Dest.Right := -MemBmp.Width;
Dest.Bottom := MemBmp.Height
end;
mtVertical:
begin
Dest.Left := 0;
Dest.Top := MemBmp.Height;
Dest.Right := MemBmp.Width;
Dest.Bottom := -MemBmp.Height
end;
mtBoth:
begin
Dest.Left := MemBmp.Width;
Dest.Top := MemBmp.Height;
Dest.Right := -MemBmp.Width;
Dest.Bottom := -MemBmp.Height
end;
end; { case MirrorType }
StretchBlt(MemBmp.Canvas.Handle, Dest.Left, Dest.Top, Dest.Right, Dest.Bottom,
MemBmp.Canvas.Handle, 0, 0, MemBmp.Width, MemBmp.Height,
SRCCOPY);
Picture.Graphic.Assign(MemBmp);
Invalidate
finally
FreeAndNil(MemBmp)
end; { try }
end; { Assigned(Picture.Graphic) }
end; { Mirror }
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