CopyRect not working under Linux?
lazarus / 39-Graphics

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han · 2017-12-07 22:37

I working on a code conversion from Windows to Linux and have an odd
problem I can't fix. The program works with images and requires a
horizontal and vertical flip of an Timage. It works in Window but not
under Linux (fpc 3.0.2 and 3.0.4). I have impression the CopyRect
doesn't work. Below my routine. Why doesn't it work in Linux and how
to fix?

procedure Tmainwindow.Fliphorizontal1Click(Sender: TObject);
var src, dest: TRect;
    bmp: TBitmap;
    w, h: integer;
begin
  w:=image1.Picture.Width; h:=image1.Picture.Height;
  dest:=bounds(0, 0, w, h);
  //src:=rect(0, h, w, 0); // Vertical flip
  src:=rect(w, 0, 0, h); // Horizontal flip
  //src:=rect(w, h, 0, 0); // Both flip
  bmp:=TBitmap.Create;
  bmp.PixelFormat:=pf24bit;
  bmp.SetSize(w, h);
  bmp.Canvas.Draw(0, 0, image1.Picture.Bitmap);
  image1.Picture.Bitmap.Canvas.CopyRect(dest, bmp.Canvas, src);
  bmp.Free;
end;

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Blaazen · 2017-12-07 23:22

Hi, this works under Linux (Qt):
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i   ... 
dest:=rect(w, 0, 0, h); 
image1.Picture.Bitmap.Canvas.StretchDraw(dest, bmp);

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han · 2017-12-08 07:53

Yes that works!. I'm not a fan of StrechDraw since it can result in
distortions. The application is an astronomical application and should
be correct on subpixel level.

Later, I found a way to fix the CopyRect routine:

This works only in MS-Windows
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
 src:=rect(w, 0, 0, h);  dest:=bounds(0, 0, w, h);
This works both in MS-Windows and Linux:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
src:=rect(0, 0, w, h);dest:=rect(w, 0, 0, h);//horizontal flip
Weird, is this a bug?

This is the new procedure working both in MS-Windows and Linux:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
Tmainwindow.Fliphorizontal1Click(Sender: TObject);var src, dest:
TRect;    bmp: TBitmap;    w, h: integer;begin 
w:=image1.Picture.Width; h:=image1.Picture.Height;  src:=rect(0, 0, w,
h);  dest:=rect(w, 0, 0, h);//horizontal flip  bmp:=TBitmap.Create; 
bmp.PixelFormat:=pf24bit;  bmp.SetSize(w, h);  bmp.Canvas.Draw(0, 0,
image1.Picture.Bitmap);  image1.Picture.Bitmap.Canvas.CopyRect(dest,
bmp.Canvas, src);  bmp.Free;end;

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han · 2017-12-08 09:33

The same effect with StretchDraw if line 13 is replaced with:

     image1.Picture.Bitmap.Canvas.StretchDraw(dest, bmp);    

Is this a different behavior inside Linux?

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Blaazen · 2017-12-08 16:27

Yes, both CopyRect and StrechDraw work in Linux now. I don't if that
trick of swapping Src and Dest rectangles is a bug, although.