Transfarent Bitmap

unit TransBitU;

interface

uses

Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,

StdCtrls, Spin, ExtCtrls;

type

TForm1 = class(TForm)

ImgBackground1: TImage;

ImgTransparent1: TImage;

SpinEdit1: TSpinEdit;

SpinEdit2: TSpinEdit;

Label1: TLabel;

Label2: TLabel;

ImgSprite1: TImage;

ImgMask1: TImage;

Label3: TLabel;

Label4: TLabel;

Label5: TLabel;

Label6: TLabel;

imgDrawn1: TImage;

Label7: TLabel;

Button1: TButton;

procedure SpinEdit1Change(Sender: TObject);

procedure FormCreate(Sender: TObject);

procedure Button1Click(Sender: TObject);

private

{ Private declarations }

public

{ Public declarations }

end;

var

Form1: TForm1;

initialized: boolean; // used to indicate when the sprite and mask are made

implementation

{$R *.DFM}

procedure initialize;

const TranspColour=clBlack; // the colour of pixels that will be made invisible

begin // creates the mask and sprite

with form1 do

begin

imgMask1.Height:=imgTransparent1.Height;

imgMask1.Width:=imgTransparent1.Width;

imgSprite1.Height:=imgTransparent1.Height;

imgSprite1.Width:=imgTransparent1.Width;

// now the images have their dimensions equal

// Now, start creating the Mask

imgMask1.Canvas.Draw(0,0,imgTransparent1.Picture.Bitmap);// copy the image

imgMask1.Picture.Bitmap.Mask(TranspColour);

// The mask is now created.

//Now, start creating the sprite

imgSprite1.Canvas.Draw(0,0,imgMask1.Picture.Bitmap);

imgSprite1.Canvas.Pen.Mode:=pmnot; // not mode for inverting the colours of the mask

imgSprite1.Canvas.Rectangle(-1,-1,imgSprite1.Width+1,imgSprite1.Height+1);

// invert colours of the mask

imgSprite1.Canvas.CopyMode:=cmSrcAnd; // and mode

imgSprite1.Canvas.Draw(0,0,imgTransparent1.Picture.Bitmap);

// Sprite is now created.

imgDrawn1.Height:=imgBackground1.Height;

imgDrawn1.Width:=imgBackground1.Width;

// the background now has the dimensions of the background

end;

initialized:=true;

// indicate that the mask, and sprite has been created

end;

procedure TForm1.SpinEdit1Change(Sender: TObject);

// Draw the transparent bitmap

var

x,y: integer; // top,left coordinates of the transparent graphic

begin

if not initialized then

initialize; // Create the mask and sprite, if hasn't been done yet.

x:=spinedit1.value;

y:=spinedit2.value; // get the input coordinates

imgDrawn1.Canvas.Draw(0,0,imgBackground1.Picture.Bitmap); // copy the background into the image

imgDrawn1.Canvas.CopyMode:=cmSrcAnd; // and mode

imgDrawn1.Canvas.Draw(x,y,imgMask1.Picture.Bitmap);

// Mask drawn

imgDrawn1.Canvas.CopyMode:=cmSrcPaint; // or mode

imgDrawn1.Canvas.Draw(x,y,imgSprite1.Picture.Bitmap);

imgDrawn1.Canvas.CopyMode:=cmSrcCopy; // the normal mode

end;

procedure TForm1.FormCreate(Sender: TObject);

begin

initialized:=false;

end;

procedure TForm1.Button1Click(Sender: TObject);

begin // initialize

initialize;

end;

end.