* Implemented the Wu Anti-Aliased line drawing algorithm. Soon the canvas DrawLine will start using it.

* Created a very quick and simple Wu Line example.

3 files changed, 173 insertions, 2 deletions

diff --git a/src/corelib/gfx_wuline.pas b/src/corelib/gfx_wuline.pas
new file mode 100644
index 00000000..ce5c403b
--- /dev/null
+++ b/src/corelib/gfx_wuline.pas
@@ -0,0 +1,167 @@
+{
+    fpGUI  -  Free Pascal GUI Library
+
+    Copyright (C) 2006 - 2007 See the file AUTHORS.txt, included in this
+    distribution, for details of the copyright.
+
+    See the file COPYING.modifiedLGPL, included in this distribution,
+    for details about redistributing fpGUI.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+
+    Description:
+
+      A Object Pascal implemenation of Wu Anti-Aliased Lines.
+      For details about the algorithm have a look at:
+        http://freespace.virgin.net/hugo.elias/graphics/x_wuline.htm
+      Here is an implementation in C++
+        http://www.codeproject.com/gdi/antialias.asp
+}
+unit gfx_wuline;
+
+{$mode objfpc}{$H+}
+
+interface
+
+uses
+  Classes, SysUtils, gfxbase, fpgfx;
+
+
+procedure WuLine(ACanvas: TfpgCanvas; Point1, Point2: TPoint; AColor: TfpgColor);
+procedure DrawWuCircle(Canvas: TfpgCanvas; x, y, r: integer; AColor: TfpgColor);
+
+
+implementation
+
+
+type
+  // to get access to Protected fields
+  TCanvasHack = class(TfpgCanvas);
+  
+
+// Blend a pixel with the current colour
+procedure AlphaBlendPixel(ACanvas: TfpgCanvas; X, Y: integer; R, G, B: word; ARatio: Double);
+var
+  LBack, LNew: TRGBTriple;
+  LMinusRatio: Double;
+begin
+  if (X < 0) or (X > TCanvasHack(ACanvas).FWindow.Width - 1) or (Y < 0) or
+     (Y > TCanvasHack(ACanvas).FWindow.Height - 1) then
+    Exit; // clipping
+
+  LMinusRatio := 1 - ARatio;
+  LBack       := fpgColorToRGBTriple(ACanvas.Pixels[X, Y]);
+  LNew.Blue   := round(B*ARatio + LBack.Blue*LMinusRatio);
+  LNew.Green  := round(G*ARatio + LBack.Green*LMinusRatio);
+  LNew.Red    := round(R*ARatio + LBack.Red*LMinusRatio);
+  ACanvas.Pixels[X, Y] := RGBTripleTofpgColor(LNew);
+end;
+
+// Draw a anti-aliased line
+procedure WuLine(ACanvas: TfpgCanvas; Point1, Point2: TPoint; AColor: TfpgColor);
+var
+  deltax, deltay, loop, start, finish: integer;
+  dx, dy, dydx: single; // fractional parts
+  LR, LG, LB: word;
+  x1, x2, y1, y2: integer;
+begin
+  x1      := Point1.X;
+  y1      := Point1.Y;
+  x2      := Point2.X;
+  y2      := Point2.Y;
+  deltax  := abs(x2 - x1); // Calculate deltax and deltay for initialisation
+  deltay  := abs(y2 - y1);
+  
+  if (deltax = 0) or (deltay = 0) then  // straight lines
+  begin
+    ACanvas.SetColor(AColor);
+    ACanvas.DrawLine(x1, y1, x2, y2);
+    Exit; //==>
+  end;
+  LR := fpgGetRed(AColor);
+  LG := fpgGetGreen(AColor);
+  LB := fpgGetBlue(AColor);
+  if deltax > deltay then
+  begin // horizontal or vertical
+    if y2 > y1 then // determine rise and run
+      dydx := -(deltay / deltax)
+    else
+      dydx := deltay / deltax;
+      
+    if x2 < x1 then
+    begin
+      start   := x2; // right to left
+      finish  := x1;
+      dy      := y2;
+    end
+    else
+    begin
+      start   := x1; // left to right
+      finish  := x2;
+      dy      := y1;
+      dydx    := -dydx; // inverse slope
+    end;
+    
+    for loop := start to finish do
+    begin
+      AlphaBlendPixel(ACanvas, loop, trunc(dy), LR, LG, LB, 1 - frac(dy));
+      AlphaBlendPixel(ACanvas, loop, trunc(dy) + 1, LR, LG, LB, frac(dy));
+      dy := dy + dydx; // next point
+    end;
+  end
+  else
+  begin
+    if x2 > x1 then // determine rise and run
+      dydx := -(deltax / deltay)
+    else
+      dydx := deltax / deltay;
+      
+    if y2 < y1 then
+    begin
+      start   := y2; // right to left
+      finish  := y1;
+      dx      := x2;
+    end
+    else
+    begin
+      start   := y1; // left to right
+      finish  := y2;
+      dx      := x1;
+      dydx    := -dydx; // inverse slope
+    end;
+    
+    for loop := start to finish do
+    begin
+      AlphaBlendPixel(ACanvas, trunc(dx), loop, LR, LG, LB, 1 - frac(dx));
+      AlphaBlendPixel(ACanvas, trunc(dx) + 1, loop, LR, LG, LB, frac(dx));
+      dx := dx + dydx; // next point
+    end;
+  end;
+end;
+
+// A very basic circle implementation. Not to pretty, but it works.
+procedure DrawWuCircle(Canvas: TfpgCanvas; x, y, r: integer; AColor: TfpgColor);
+var
+	x1, y1, x2, y2: integer;
+	dt: integer;
+  theta: integer;
+begin
+  theta := 0;
+  dt := 4;
+  while theta < 360 do
+  begin
+		x1 := round( r*cos(theta*pi/180.0)+x);
+		y1 := round(-r*sin(theta*pi/180.0)+y);
+
+		x2 := round( r*cos((theta+dt)*pi/180.0)+x);
+		y2 := round(-r*sin((theta+dt)*pi/180.0)+y);
+
+		WuLine(Canvas, Point(x1, y1), Point(x2, y2), AColor);
+    theta := theta + dt;
+  end;
+end;
+
+end.
+
diff --git a/src/corelib/x11/fpgfx_package.lpk b/src/corelib/x11/fpgfx_package.lpk
index 49ac5b3a..6536d8e5 100644
--- a/src/corelib/x11/fpgfx_package.lpk
+++ b/src/corelib/x11/fpgfx_package.lpk
@@ -24,7 +24,7 @@
     <License Value="Modified LGPL
 "/>
     <Version Minor="5" Release="1"/>
-    <Files Count="17">
+    <Files Count="18">
       <Item1>
         <Filename Value="x11_xft.pas"/>
         <UnitName Value="x11_xft"/>
@@ -93,6 +93,10 @@
         <Filename Value="../gfx_command_intf.pas"/>
         <UnitName Value="gfx_command_intf"/>
       </Item17>
+      <Item18>
+        <Filename Value="../gfx_wuline.pas"/>
+        <UnitName Value="gfx_wuline"/>
+      </Item18>
     </Files>
     <LazDoc Paths="../../../docs/xml/corelib/;../../../docs/xml/corelib/x11/;../../../docs/xml/corelib/gdi/"/>
     <RequiredPkgs Count="1">
diff --git a/src/corelib/x11/fpgfx_package.pas b/src/corelib/x11/fpgfx_package.pas
index d3ec9058..34e24d16 100644
--- a/src/corelib/x11/fpgfx_package.pas
+++ b/src/corelib/x11/fpgfx_package.pas
@@ -10,7 +10,7 @@ uses
   x11_xft, x11_keyconv, gfxbase, gfx_x11, fpgfx, gfx_stdimages, gfx_imgfmt_bmp, 
     gfx_widget, gfx_UTF8utils, gfx_extinterpolation, gfx_cmdlineparams, 
     gfx_clipboard, gfx_utils, gfx_popupwindow, gfx_impl, gfx_strings, 
-    gfx_command_intf; 
+    gfx_command_intf, gfx_wuline; 
 
 implementation