Peripheral drift illusion: Difference between revisions

=={{header|Delphi}}==

{{works with|Delphi|6.0}}

{{libheader|SysUtils,StdCtrls}}

<syntaxhighlight lang="Delphi">

{The illusion works by drawing light/dark edges around

{the squares in an inconsistent pattern that confuses}

{the eye about whethe squares are raise or lowered}

{Specifies corner on which the white lines are drawn}

type TCorners = (crTopLeft = 0,crTopRght = 1,crBtmLeft = 3,crBtmRght = 2);

{Array of edge patterns}

const Edges: array [0..12-1] of array [0..12-1] of TCorners =(

(crTopLeft, crBtmLeft, crBtmLeft, crBtmRght, crBtmRght, crTopRght, crTopRght, crTopLeft, crTopLeft, crBtmLeft, crBtmLeft, crBtmRght),

(crTopLeft, crTopLeft, crBtmLeft, crBtmLeft, crBtmRght, crBtmRght, crTopRght, crTopRght, crTopLeft, crTopLeft, crBtmLeft, crBtmLeft),

(crTopRght, crTopLeft, crTopLeft, crBtmLeft, crBtmLeft, crBtmRght, crBtmRght, crTopRght, crTopRght, crTopLeft, crTopLeft, crBtmLeft),

(crTopRght, crTopRght, crTopLeft, crTopLeft, crBtmLeft, crBtmLeft, crBtmRght, crBtmRght, crTopRght, crTopRght, crTopLeft, crTopLeft),

(crBtmRght, crTopRght, crTopRght, crTopLeft, crTopLeft, crBtmLeft, crBtmLeft, crBtmRght, crBtmRght, crTopRght, crTopRght, crTopLeft),

(crBtmRght, crBtmRght, crTopRght, crTopRght, crTopLeft, crTopLeft, crBtmLeft, crBtmLeft, crBtmRght, crBtmRght, crTopRght, crTopRght),

(crBtmLeft, crBtmRght, crBtmRght, crTopRght, crTopRght, crTopLeft, crTopLeft, crBtmLeft, crBtmLeft, crBtmRght, crBtmRght, crTopRght),

(crBtmLeft, crBtmLeft, crBtmRght, crBtmRght, crTopRght, crTopRght, crTopLeft, crTopLeft, crBtmLeft, crBtmLeft, crBtmRght, crBtmRght),

(crTopLeft, crBtmLeft, crBtmLeft, crBtmRght, crBtmRght, crTopRght, crTopRght, crTopLeft, crTopLeft, crBtmLeft, crBtmLeft, crBtmRght),

(crTopLeft, crTopLeft, crBtmLeft, crBtmLeft, crBtmRght, crBtmRght, crTopRght, crTopRght, crTopLeft, crTopLeft, crBtmLeft, crBtmLeft),

(crTopRght, crTopLeft, crTopLeft, crBtmLeft, crBtmLeft, crBtmRght, crBtmRght, crTopRght, crTopRght, crTopLeft, crTopLeft, crBtmLeft),

(crTopRght, crTopRght, crTopLeft, crTopLeft, crBtmLeft, crBtmLeft, crBtmRght, crBtmRght, crTopRght, crTopRght, crTopLeft, crTopLeft));

{Base colors}

const LightOlive: TColor = $04D0D3;

const PaleBlue: TColor = $FF523E;

{Patterns of edge colors}

type TColorArray = array [0..4-1] of array [0..4-1] of TColor;

const Colors: TColorArray = (

(clWhite, clBlack, clBlack, clWhite),

(clWhite, clWhite, clBlack, clBlack),

(clBlack, clWhite, clWhite, clBlack),

(clBlack, clBlack, clWhite, clWhite));

procedure DrawEdge(Canvas: TCanvas; PX, PY, Size: integer; Colors: TColorArray; Edge: TCorners);

{Draw edges around square}

begin

Canvas.MoveTo(PX, PY);

Canvas.Pen.Color:=Colors[Integer(Edge),0];

Canvas.LineTo(PX+Size, PY);

Canvas.Pen.Color:=Colors[Integer(Edge),1];

Canvas.LineTo(PX+Size, PY+Size);

Canvas.Pen.Color:=Colors[Integer(Edge),2];

Canvas.LineTo(PX, PY+Size);

Canvas.Pen.Color:=Colors[Integer(Edge),3];

Canvas.LineTo(PX, PY);

end;

procedure DrawPeripheralDrift(Image: TImage);

{Draw Peripheral Drift illusion}

var WWidth,WHeight: integer;

var X,Y,PX,PY: integer;

var SqrSize,Border,Spacing,InSquare,CellSize: integer;

begin

{Calculate base size from window size}

WWidth:=Min(Image.Width,Image.Height);

WHeight:=WWidth;

{Calculate border, square and spacing from base size}

InSquare:=MulDiv(WWidth,780,1000);

Border:=(WWidth-InSquare) div 2;

CellSize:=InSquare div 12;

SqrSize:=MulDiv(CellSize,75,100);

Spacing:=MulDiv(CellSize,25,100);

{Draw background rectangel}

Image.Canvas.Brush.Color:=LightOlive;

Image.Canvas.Rectangle(0,0,WWidth,WHeight);

{Draw 12x12 grid of squares}

for X:= 0 to 12-1 do

begin

PX:= Border + X*CellSize;

for Y:= 0 to 12-1 do

begin

PY:= Border + Y*CellSize;

{Draw square}

Image.Canvas.Brush.Color:=PaleBlue;

Image.Canvas.Pen.Color:=PaleBlue;

Image.Canvas.Rectangle(PX, PY, PX+SqrSize, PY+SqrSize);

{Draw edges, which causes the illusion}

DrawEdge(Image.Canvas, PX, PY, SqrSize, Colors, Edges[Y,X]);

end;

end;

Image.Invalidate;

end;

procedure ShowPeripheralDrift(Image: TImage);

begin

DrawPeripheralDrift(Image);

end;

</syntaxhighlight>

{{out}}

<pre>

Elapsed Time: 6.274 ms.

</pre>