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再学GDI+[24]: TGPLinearGradientBrush - 之三

时间:2012-05-05 | 栏目:Delphi教程 | 点击:

TGPLinearGradientBrush.Create(
 const point1, point2: TGPPoint; {线性渐变起始点与终止点}
 color1, color2: TGPColor    {线性渐变起始色与终止色}
);
TGPLinearGradientBrush.Create(
 const point1, point2: TGPPointF;
 color1, color2: TGPColor
);

本例效果图:

代码文件:unit Unit1;
interface
uses
 Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
 Dialogs, StdCtrls, TeCanvas, ExtCtrls;
type
 TForm1 = class(TForm)
  ButtonColor1: TButtonColor;
  ButtonColor2: TButtonColor;
  procedure FormCreate(Sender: TObject);
  procedure FormPaint(Sender: TObject);
  procedure ButtonColor1Click(Sender: TObject);
  procedure ButtonColor2Click(Sender: TObject);
  procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
   Shift: TShiftState; X, Y: Integer);
  procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
   Shift: TShiftState; X, Y: Integer);
  procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
 end;
var
 Form1: TForm1;
implementation
{$R *.dfm}
uses GDIPOBJ, GDIPAPI, TypInfo;
var
 pts: array[0..1] of TPoint;
 f: Boolean;
 p: 0..2;
procedure TForm1.FormCreate(Sender: TObject);
begin
 ButtonColor1.Caption := '色1   ';
 ButtonColor2.Caption := '色2   ';
 ButtonColor1.SymbolColor := clLime;
 ButtonColor2.SymbolColor := clBlack;
 pts[0].X := 8;
 pts[0].Y := 8;
 pts[1].X := ClientWidth - 10;
 pts[1].Y := ClientHeight - 10;
end;
procedure TForm1.FormPaint(Sender: TObject);
var
 g: TGPGraphics;
 p: TGPPen;
 lb: TGPLinearGradientBrush;
 c1,c2: TGPColor;
 r: TGPRect;
begin
 g := TGPGraphics.Create(Canvas.Handle);
 p := TGPPen.Create(aclRed);
 r := MakeRect(20, 40, ClientWidth - 40, ClientHeight - 50);
 c1 := ColorRefToARGB(ButtonColor1.SymbolColor);
 c2 := ColorRefToARGB(ButtonColor2.SymbolColor);
 lb := TGPLinearGradientBrush.Create(TGPPoint(pts[0]), TGPPoint(pts[1]), c1, c2);
 g.FillEllipse(lb, r);
 g.DrawRectangle(p, MakeRect(pts[0].X-2, pts[0].Y-2, 4, 4));
 g.DrawRectangle(p, MakeRect(pts[1].X-2, pts[1].Y-2, 4, 4));
 lb.Free;
 p.Free;
 g.Free;
end;
procedure TForm1.ButtonColor1Click(Sender: TObject);
begin
 Repaint;
end;
procedure TForm1.ButtonColor2Click(Sender: TObject);
begin
 Repaint;
end;
procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
 Shift: TShiftState; X, Y: Integer);
begin
 f := True;
end;
procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
 Y: Integer);
var
 i: Integer;
begin
 if f then
 begin
  if p = 0 then Exit;
  pts[p-1] := Point(X,Y);
  Repaint;
 end else begin
  p := 0;
  Cursor := crDefault;
  for i := 0 to 1 do
   if PtInRect(Bounds(pts[i].X-2, pts[i].Y-2, 4, 4), Point(X,Y)) then
   begin
    p := i+1;
    Cursor := crHandPoint;
   end;
 end;
end;
procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
 Shift: TShiftState; X, Y: Integer);
begin
 f := False;
end;
end.

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