png alpha-transparency in linux
lazarus / 39-Graphics

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cd · 2010-04-04 17:29

compare the two following
wheres alpha in linux?

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Troodon · 2010-04-04 20:02

That is antialiasing.

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cd · 2010-04-04 22:13

No, that has nothing to do with antialiasing.
That is ignoring semi-transparent alpha-channel. pixels with alpha>0.5
are shown as fully opaque, alpha<0.5 is treated as fully transparent.

The same thing concerns 32bit icons, which are displayed well in
windows, but have same coarse edge in lunix.

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Marc · 2010-04-05 22:04

Currently the routines we use for graphics drawing support 1-bit alpha
only. Change is planned, but don't count on it soon.

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cd · 2010-04-06 09:34

is the code that is used in windows os-dependent?

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Marc · 2010-04-06 10:12

Yes, in windows, winapi functions are used

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circular · 2010-04-11 17:53

Ok, i added it. Try this with BGRABitmap :

Code: [Select]uses BGRABitmap;

{...}

procedure TForm1.FormCreate(Sender: TObject);
begin
  png := TBGRABitmap.Create('somefile.png');
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  png.Free;
end;

procedure TForm1.FormPaint(Sender: TObject);
begin
  png.Draw(Canvas,0,0,False);
end;

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cd · 2010-04-12 05:21

circular

your BGRABitmap is very good, but i can't use it becaus it is GPLed.

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circular · 2010-04-12 07:43

See the other topic to continue talking about the license :
TBitmap.ScanLine