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再学GDI+[92]: TGPImage(12) - 调整图像透明度
2012-05-29 00:00:00   来源:www.bianceng.cn   评论:0 点击:

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本例效果图:

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代码文件: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: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

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