再学GDI+[92]: TGPImage（12） - 调整图像透明度

再学GDI+[92]: TGPImage（12） - 调整图像透明度2012-05-29 cnblogs 万一本例效果图:

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:	emp	est.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