Difference between revisions of "Graphics - Working with TCanvas"

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Questo può essere ottenuto con il codice seguente:
+
This can be obtained with following code:
 
<syntaxhighlight>SelectObject(Canvas.Handle, GetStockObject(DEFAULT_GUI_FONT));</syntaxhighlight>
 
<syntaxhighlight>SelectObject(Canvas.Handle, GetStockObject(DEFAULT_GUI_FONT));</syntaxhighlight>
  

Revision as of 18:02, 22 October 2016

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Using the default GUI font

!! temporary message to Nifan : could you leave this content in English please, write the Italian version in the page Graphics_-_Working_with_TCanvas/it. !!


This can be obtained with following code:

SelectObject(Canvas.Handle, GetStockObject(DEFAULT_GUI_FONT));

Disegnare un testo delimitato in larghezza

Utilizzare la routine DrawText, prima con il parametro DT_CALCRECT e poi senza.

// First calculate the text size then draw it
TextBox := Rect(0, currentPos.Y, Width, High(Integer));
DrawText(ACanvas.Handle, PChar(Text), Length(Text),
  TextBox, DT_WORDBREAK or DT_INTERNAL or DT_CALCRECT);

DrawText(ACanvas.Handle, PChar(Text), Length(Text),
  TextBox, DT_WORDBREAK or DT_INTERNAL);

Drawing text with sharp edges (non antialiased)

Some widgetsets support this via

Canvas.Font.Quality := fqNonAntialiased;

Some widgetsets like the gtk2 do not support this and always paint antialiased. Here is a simple procedure to draw text with sharp edges under gtk2. It does not consider all cases, but it should give an idea:

procedure PaintAliased(Canvas: TCanvas; x,y: integer; const TheText: string);
var
  w,h: integer;
  IntfImg: TLazIntfImage;
  Img: TBitmap;
  dy: Integer;
  dx: Integer;
  col: TFPColor;
  FontColor: TColor;
  c: TColor;
begin
  w:=0;
  h:=0;
  Canvas.GetTextSize(TheText,w,h);
  if (w<=0) or (h<=0) then exit;
  Img:=TBitmap.Create;
  IntfImg:=nil;
  try
    // paint text to a bitmap
    Img.Masked:=true;
    Img.SetSize(w,h);
    Img.Canvas.Brush.Style:=bsSolid;
    Img.Canvas.Brush.Color:=clWhite;
    Img.Canvas.FillRect(0,0,w,h);
    Img.Canvas.Font:=Canvas.Font;
    Img.Canvas.TextOut(0,0,TheText);
    // get memory image
    IntfImg:=Img.CreateIntfImage;
    // replace gray pixels
    FontColor:=ColorToRGB(Canvas.Font.Color);
    for dy:=0 to h-1 do begin
      for dx:=0 to w-1 do begin
        col:=IntfImg.Colors[dx,dy];
        c:=FPColorToTColor(col);
        if c<>FontColor then
          IntfImg.Colors[dx,dy]:=colTransparent;
      end;
    end;
    // create bitmap
    Img.LoadFromIntfImage(IntfImg);
    // paint
    Canvas.Draw(x,y,Img);
  finally
    IntfImg.Free;
    Img.Free;
  end;
end;