Message-ID: <3B1DEF45.1D46CF36@borland.newsgroups>
Date: Wed, 06 Jun 2001 18:52:21 +1000
From: Charles Hacker <reply.to@borland.newsgroups>
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Subject: Re: Antialias ?
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Alexander Adam wrote:
> 
> I've searched the web for a while but found nothing simple to use for
> antialiasing a font which is on a tcanvas, any ideas ?

I snagged this bit of code that may be of use...

By Gustavo Daud <gubah@sti.com.br> }
procedure DrawAAText(Dest: TBitmap; DX, DY: Integer; Text: String);
type
  pRGBLine = ^TRGBLine;
  TRGBLine = Array[Word] of TRGBTriple;

  {Separate R, G and B values from the color}
  procedure SeparateColor(Color: TColor; var r: Byte; var g: byte; var
b:
byte);
  begin
    R := Color and $FF0000 shr 16;
    G := Color and $00FF00 shr 8;
    B := Color and $0000FF;
  end;
var
  TempBitmap: TBitmap;
  x, y      : Integer;
  totr,
  totg,
  totb      : Integer;
  j, i      : Integer;
  Line      : pRGBLine;
  TempLine  : Array[0..1] of pRGBLine;
begin
  {Creates a temporary bitmap do work with supersampling}
  TempBitmap := TBitmap.Create;


  with TempBitmap do
  begin
    PixelFormat := pf24bit;

    {Copy attributes from previous bitmap}
    Canvas.Font.Assign(Dest.Canvas.Font);
    Canvas.Brush.Assign(Dest.Canvas.Brush);
    Canvas.Pen.Assign(Dest.Canvas.Pen);

    Canvas.Font.Size := Canvas.Font.Size * 2;

    {Make it twice larger to apply supersampling later}
    Width  := Canvas.TextWidth(Text);
    Height := Canvas.TextHeight(Text);

    {To prevent unexpected junk}
    if (Width div 2) + DX > Dest.Width then
      Width := (Dest.Width - DX) * 2;
    if (Height div 2) + DY > Dest.Height then
      Height := (Dest.Height - DY) * 2;


    {If the brush style is clear, then copy the image from the}
    {previous image to create the propher effect}
    if Canvas.Brush.Style = bsClear then
    begin
      Canvas.Draw(-DX, -DY, Dest);
      Canvas.Stretchdraw(Rect(0, 0, Width * 2, Height * 2), TempBitmap);
    end;

    {Draws the text using double size}
    Canvas.TextOut(0, 0, Text);
  end;

  {Draws the antialiased image}
  for y := 0 to ((TempBitmap.Height) div 2) - 1 do begin

    {If the y pixel is outside the clipping region, do the proper
action}
    if dy + y < 0 then
      Continue
    else if Dy + y > Dest.Height - 1 then
      Break;

    {Scanline for faster access}
    Line := Dest.ScanLine[DY + y];

    TempLine[0] := TempBitmap.Scanline[2*y];
    TempLine[1] := TempBitmap.Scanline[(2*y) + 1];

    for x := 0 to ((TempBitmap.Width) div 2) - 1 do begin

      {If the x pixel is outside the clipping region, do the proper
action}
      if dx + x < 0 then
        Continue
      else if Dx + x > Dest.Width - 1 then
        Break;

      {Compute the value of the output pixel (x, y) }
      TotR := 0;
      TotG := 0;
      TotB := 0;

      for j := 0 to 1 do begin
        for i := 0 to 1 do
          with TempLine[j][2*x+i] do begin

            inc(TotR, rgbtRed); inc(TotG, rgbtGreen); inc(TotB,
rgbtBlue);
          end;
      end;

      {Set the pixel values thru scanline}
      with Line[DX + x] do
      begin
        rgbtRed := TotR div 4;
        rgbtGreen := TotG div 4;
        rgbtBlue := TotB div 4;
      end;

    end;
  end;

  {Free the temporary bitmap}
  TempBitmap.Free;
end;

-- 
Charles Hacker
Lecturer in Electronics and Computing
School of Engineering
Griffith University - Gold Coast
Australia