再学 GDI+[92]: TGPImage(12) - 调整图像透明度

本例效果图:

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代码文件:

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unit Unit1;



interface



uses

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

  Dialogs, StdCtrls, ComCtrls;



type

  TForm1 = class(TForm)

    TrackBar1: TTrackBar;

    procedure FormCreate(Sender: TObject);

    procedure FormPaint(Sender: TObject);

    procedure TrackBar1Change(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



uses GDIPOBJ, GDIPAPI;



var

  ColorMatrix: TColorMatrix = (

    (1.0, 0.0, 0.0, 0.0, 0.0),

    (0.0, 1.0, 0.0, 0.0, 0.0),

    (0.0, 0.0, 1.0, 0.0, 0.0),

    (0.0, 0.0, 0.0, 1.0, 0.0),

    (0.0, 0.0, 0.0, 0.0, 1.0));



procedure TForm1.FormCreate(Sender: TObject);

begin

  TrackBar1.Height := 23;

  TrackBar1.ShowSelRange := False;

  TrackBar1.Max := 100;

  TrackBar1.Position := TrackBar1.Max;



  DoubleBuffered := True;

end;



procedure TForm1.FormPaint(Sender: TObject);

var

  g: TGPGraphics;

  img: TGPImage;

  ImageAttributes: TGPImageAttributes;

begin

  g := TGPGraphics.Create(Canvas.Handle);

  img := TGPImage.Create('c:\temp\test.png');



  ImageAttributes := TGPImageAttributes.Create;



  {TColorMatrix 数组的 [3,3] 决定透明度}

  ColorMatrix[3,3] := TrackBar1.Position / 100;

  ImageAttributes.SetColorMatrix(ColorMatrix);



  g.DrawImage(img,

              MakeRect(0, 0, img.GetWidth, img.GetHeight),

              0,

              0,

              img.GetWidth,

              img.GetHeight,

              UnitPixel,

              ImageAttributes

              );



  ImageAttributes.Free;

  img.Free;

  g.Free;

end;



procedure TForm1.TrackBar1Change(Sender: TObject);

begin

  Repaint;

end;



end.


 
   

窗体文件:

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object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 267

  ClientWidth = 316

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  Position = poDesktopCenter

  OnCreate = FormCreate

  OnPaint = FormPaint

  PixelsPerInch = 96

  TextHeight = 13

  object TrackBar1: TTrackBar

    Left = 0

    Top = 240

    Width = 305

    Height = 45

    TabOrder = 0

    OnChange = TrackBar1Change

  end

end